GB2105043A - Halide ion selective electrode - Google Patents

Abstract

A halide selective electrode comprises a base layer of silver or a semi-conductor material such as silicon dioxide/silicon, having provided thereon, in sequence, a silver halide layer and a layer capable of permeation by halogen ions to be measured and composed of a polymer latex, a copolymer or a polymer blend. By the provision of the polymer layer, a concentration or activity of halogen ions can be accurately measured in a shortened period of time without interference by uric acid, halogen ions other than those to be measured or other interfering low molecular weight substances.

Description

SPECIFICATION lon selective electrode for measuring halogen ions BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to an improved electrode for measuring halogen ions which is capable of measuring a concentration or acitivity of halogen ions in terms of a potential which varies depending upon their concentration or activity. The present invention further relates to a device for measuring a potential, useful for measuring halogen ions, in which such an electrode is incorporated.

The term "electrode" as used herein refers to an electrode in the same sense as that is generally called a half cell or monopole.

DEVELOPMENT OF THE INVENTION It is well known to employ silver halide for measuring halogen ions and silver/silver halide electrodes are very often used for this purpose. Further, electrodes which comprise connecting a lead wire directly to a tablet made of silver halide are also known (see, U.S. Patents 3,502,560, 3,591,482 and 3,856,649; Research Disclosure, vol. 161, No. 16113, September, 1977, etc.).These known silver/silver halide electrodes can be employed both as reference electrodes and as electrodes for measuring halogen ions; when a concentration or activity of halogen ions in a solution is attempted to measure a concentration or activity of halogen ions in a solution using these electrodes, however, a potential generated is affected due to interference by other halogen ions, e.g., bromine ions when measuring chlorine ions, or uric acid and other low molecular weight compounds, present in the solution brought into contact with the electrodes.

As a result, it is impossible to accurately measure a concentration or activity of desired halogen ions.

For the purposes of removing such so-called interfering substances, a method for coating the surface of silver/silver chloride electrodes with an alkyl acrylate layer has been proposed (U.S.

Patent 3,591,482). On the other hand, it has been proposed in platinum electrodes for measuring activity of hydrogen peroxide that electrodes are coated with a covering made of cellulose esters, silicone rubber, methyl methacrylate, etc. to which a property of allowing to permeate ions to be measured but preventing other interfering substances (e.g., uric acid or other low molecular weight substances) from permeating is imparted (U.S. Patent 3,979,274).

Ion selective electrodes having a property of selectively permeating only ions to be measured therethrough have also been proposed (Proc. Analyt. Div. Chem. Soc., pages 332 to 334 (1977). On the other hand, a method for protecting silver/silver chloride electrodes with hydrophilic resin, etc. such as epoxy resin or the like is described in Japanese Utility Model Application 14472/65. In these conventional techniques, however, it is difficult to say that operation for measurement is simple and moreover, the time required for stabilizing a potential generated (so called 'drift phenomenon") is prolonged; therefore, the conventional techniques involve problems in practical use.

In Japanese Patent Application (OPI) 89741/80 (the term "OPI" as used herein refers to an application which is unexamined but open to public inspection), electrodes which comprise laminating, in sequence, a silver layer, a silver chloride layer and a chlorine ion-permeable coating layer composed of a water-insoluble polymer represented by cellulose esters and electrochemically contacting the silver chloride layer with a means for measuring a potential difference are disclosed as electrodes for measuring a concentration or activity of chlorine ions in body fluids such as blood serum. It is said that according to these electrodes, a potential generated in response to a concentration or activity of chlorine ions is measured and the measurement is enabled for a short period of time without undergoing interference of interfering substances.

However, cellulose esters useful for forming a coated layer for capable of permeating chlorine ions are insoluble in water and, accordingly, volatile organic solvents such as acetone, methyl ethyl ketone, etc. must be used in providing the coated layer. At the present time, there is a tendency to avoid at all costs the use of volatile organic solvents is avoided in every way in chemical factories because there is a danger of accidental exploitation in handling, or, much more cause these solvents may cause environmental contamination.In spite of this, waterinsoluble polymers that are inevitably accompanied by the use of such organic solvents should have been employed as raw materials for the chlorine ion-permable coated layer in Japenese Patent Application (OPI) 89741 /80; a main reason therefor is because chlorine (or halogen) ions to be measured are exclusively present in an aqueous medium. If an ion-permeable coated layer is composed of a material which is naturally soluble in water, the coated layer is dissolved by a sample liquid such as serum or the like when it is brought into contact with the sample liquid; as a result, a stable potential cannot be obtained and, interfering substances to be removed are also brought into contact with electrodes together with ions to be measured to thereby generate an interference potential. Thus, serious errors or biased results are found in the measurement data.

With respect to coated electrodes per se---although they are not for measuring halogen ions, various techniques for coating electrodes are reported in U.S. Patents 3,694,163, 3,912,614 and 3,979,274, Proc. Analyt. Div. Chem. Soc., pages 332 to 334, November (1977), etc. However, these surface coatings are not applicable to measurement of halogen ions as they are, in which permeation of particular interfering substances should be prevented, although they can function as protective layers of the body of the electrodes.Further, even if these coating techniques are substitutable in silver halide electrodes for analyzing halogen ions in any manner, a considerable period of time is required until halogen ions in a solution permeate through these coated layers and are brought into contact with the body of the electrodes so that these electrodes cannot contribute to speedy operation of analysis.

In Japanese Patent Application (OPI) 89741 /80, cellulose esters or (meth)acrylic acid polymers are disclosed as a coating composition which can physically protect electrodes, selectively permeate halogen ions alone and as a result, assist in shortening the time period for analysis. These compositions for a coated layer cannot achieve their purpose unless they meet specific parameters for diffusion coefficient as well as permeability; it is described therein that, for example, polyvinyl acetate, polyvinyl chloride, cellulose, polyvinyl pyrrolidone, etc. cannot achieve the foregoing purpose since they do not meet the defined parameters for diffusion coefficient or permeability.As discussed above, it is a technical acknowledgement in the art of electrodes for measuring halogen ions that, in order to provide a coated layer on electrodes capable of permeating and diffusing halogen ions alone to be measured but incapable of allowing to permeate other interfering substances, a coating composition satisfying the parameters as defined in Japanese Patent Application (OPI) 89741/80 should be employed and, if a coating composition which does not meet the parameters so defined is employed, a coated layer having good protecting function or good ion selectivity can not be obtained.

Further, more importantly, a sample solution is aqueous in most cases and accordingly, only water-insoluble polymers can generally be employed as a coating composition, as discussed above. If a water-soluble coating composition is employed, coated electrodes using such a composition would be dissolved out and broken when brought into contact with a sample solution; the coated layer is no longer maintained.

As a result of investigations on compositions for a halogen ion-permeable coated layer for forming a surface coating for silver/silver halide electrodes for measuring halogen ions, in particular, suited for rapid analysis without involving the foregoing disadvantages observed in the prior art, the present inventors have found that electrodes suitable for use as electrodes for measuring halogen ions can be obtained by providing an ion-permeable coated layer using a polymer latex. The present inventors have also found that a coated layer having excellent efficiency can be unexpectely formed when copolymers of at least two monomers constituting homopolymers, or a blend of at least two homopolymers which are recognized in the art to be ineffective are employed.

SUMMARY OF THE INVENTION The present invention relates to an electrode for measuring halogen ions which comprises silver halide as a substance for detecting halogen ions having provided on the surface of the silver halide a coated layer capable of allowing permeation of aimed halogen ions, in which the coated layer capable of allowing permeation of the halogen ions (hereafter referred to as "coated layer" of sometimes as "protective layer") is composed of a polymer latex.

The present invention further relates to an electrode for measuring halogen ions which comprises silver halide as a substance for detecting halogen ions having provided on the surface of silver halide a coated layer capable of allowing permeation of aimed halogen ions, in which the coated layer is composed of a copolymer obtained by copolymerizing at least one of monomers represented by formula (V) described hereafter and at least one of monomers represented by formula (Vl) described hereafter.

The present invention further relates to an electrode for measuring halogen ions which comprises silver halide as a substance for detecting halogen ions having provided on the surface of the silver halide a coated layer capable of allowing permeation of aimed halogen ions, in which the coated layer is composed of a polymer blend of at least one of hydrophobic polymers selected from Group (AAA) described hereafter and at least one of hydrophilic polymers selected from Group (BBB) described hereafter.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph showing a potential-time response in the case of using one embodiment of the electrode in accordance with the present invention.

Fiaure 2 is a paraph showing a Cl- content-potential response in the case of using another embodiment of the electrode in accordance with the present invention.

Figure 3 is a graph showing a Cl - content-potential response in the case of a further embodiment of the electrode in accordance with the present invention.

Figures 4 and 5 are graphs showing a potential-time response obtained in the case of using various embodiments of the electrode for measuring halogen ions in accordance with the present invention, respectively.

Figure 6 is a graph showing a Cl- content-potential response obtained in the case of using one example of the electrode in accordance with the present invention.

Figure 7 is a graph showing a potential-time response obtained in the case of using an electrode (Sample 2) for measuring halogen ions embodying the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION Polymer latexes which are employed as materials for the coated layer can form a waterinsoluble coated layer, notwithstanding that they can be applied in the form where the latexes are emulsified and dispersed in water. That is, once the coated layer is formed, this coated layer becomes insoluble in a sample liquid even when the coated layer is brought into contact with the sample liquid. When the technical background that water-insoluble polymers necessarily accompanied by the use of organic solvents should have been chosen in the step of preparing electrodes disclosed in Japanese Patent Application (OPI) 89741 /80 (corresponding to U.S.

Patents 4,199,411 and 4,199,412) is taken into account, it is quite surprising that latexes could be used in a state where they are emuslified and dispersed in water.

The electrode in accordance with the present invention is characterized in that, in an electrode for measuring halogen ions comprising silver halide, as a substance for detecting halogen ions, having provided a coated layer capable of permeating desired halogen ions at the surface of the silver halide, the coated layer capable of allowing permeation of the halogen ions (hereafter merely referred to as "coated layer") is composed of a polymer latex.

The coated layer is formed in accordance with a conventional technique for forming a layer using a polymer latex obrained by emulsion polymerization of monomers described hereafter in such a concentration as is synthesized, or after further diluting the polymer latex with water at an appropriate concentration that is suitable for coating operation.

Representative examples of polymer latexes are as follows, wherein the alkyl moiety or group of alkyl nature including a substituent(s) thereon has 1 to about 20 carbon atoms and the aryl moiety or group of aryl nature including a substituent(s) thereon has 6 to about 1 2 carbon atoms, and examples of the substituents include alkyl, aryl, alkoxy-carbonyl groups and a halogen atom such as chlorine, fluorine, iodine, etc., unless otherwise indicated.

I. Polymer Latex (I): Polymer latex produced by emulsion polymerization of each of at least one monomer selected from the group consisting of monomers of Group (A), at least one monomer selected from the group consisting of monomers of Group (B) and at least one monomer selected from the group consisting of monomers of Group (C): Group (A): Ethylene-type monomers having at least one free carboxylic acid group, free sulfonic acid group or a free phosphoric acid group or a salt thereof: Group (B): Monomers represented by formula (IB):

wherein X, V: hydrogen atom, methyl group, halogen atom, or -COOR1 group Y: hydrogen atom, methyl group, halogen atom or -(CH2)nCOOR2 Z: aryl group, -COOR3 or -OCOR5 R', R2, R3: they may be the same or different and represent an aliphatic group or an aryl group.

n: O, 1,2 or 3 Group (C): Unsaturated monomers other than monomers belonging to Group (A) and Group (B) and copolymerizable with monomers of Group (A) or Group (B): Monomers for Group (C) are specifically selected from acrylamindes, methacrylamindes, vinyl ethers, vinyl ketones, allyl compounds, olefins, vinyl heterocyclic compounds, unsaturated nitriles and polyfunctional monomers.

The coated layer contained in the electrode in accordance with the present invention can further be composed of a copolymer obtained by copolymerizing at least one of hydrophobic monomers (AA) represented by formula (V) below and at least one of hydrophilic monomers (BB) represented by formula (VI) below: Hydrophobic Monomer (AA):

Hydrophilic Monomer (BB):

In formula (V), R'O represents a hydrogen atom, an alkyl group, or a halogen atom;R20 represents an alkyl group, a substituted alkyl group, an alkoxycarbonyl group, a substituted alkoxycarbonyl group, an alkoxycarbonylalkyl group, an alkycarboxy group, a substituted alkylcarboxy group, an alkylcarboxylalkyl group, a substituted alkylcarboxyalkyl group, an aryl group, a substituted aryl group, a monoalkylaminocarbonyl group, a substituted monoalkylaminocarbonyl group, a dialkylaminocarbonyl group, a substituted dialkylaminocarbonyl group or a halogen atom.

In formula (VI), R30 represents a hydrogen atom or an alkyl group; R40 represents a

nucleus (wherein Z represents an atomic group necessary for completing a pyrrolidone nucleus, an imidazole nucleus, an oxazolone nucleus or a succinimido nucleus), a 2-pyridyl group, a 4pyridyl group, a hydroxycarbonyl group, an aminocarbonyl group, an alkylaminocarbonyl group, a substituted alklaminocarbonyl group, a dialkylaminocarbonyl group, a substituted dialkylaminocarbonyl group, a sulfonyl group, a hydroxy group, an amino group, a substituted amino group, a carboxyaryl group, a sulfoaryl group, a hydroxyethoxycarbonyl group, a sulfonic acid group, a phosphoric acid group, a substituted alkoxy group.

In another embodiment of the present invention, the coated layer can also be composed of a polymer blend of at least one of hydrophobic polymers selected from Group (AAA) described below and at least one of hydrophilic polymers selected from Group (BBB) described below.

(AAA) Hydrophobic Polymer (AAA-1): Hydrophobic polymers obtained by polymerizing at least one monomer represented by formula (V) above: (AAA-2): Polyamides (AAA-3): Ethyl cellulose (BBB) Hydrophilic Polymer (BBB-1): Hydrophilic polymers obtained by polymerizing at least one monomer represented by formula (VI) above: (BBB-2): Polyethylene glycol (BBB-3): Methyl cellulose (BBB-4): Carboxymethyl cellulose (BBB-5): Hydroxyethyl cellulose (BBB-6): Maleic acid polymers (BBB-7): Maleic anhydride polymers (BBB-8): Fumaric acid polymers The blend of the polymers described above that is employed in the coated layer constituting the electrode in accordance with the present invention is obtained by selecting one each from Group (AAA) and Group (BBB) and blending them.While there is no particular criterion for the selection, it is sufficient to maintain a coating property to an extent that the resulting coated layer is not destroyed by a sample liquid when the sample liquid was dropped onto the coated layer. Of combinations of the above polymers, a blend of a hydrophobic copolymer belonging to (AAA-1) and a hydrophobic homopolymer or copolymer belonging to (BBB-1), and a blend of a hydrophobic homopolymer belonging to (AAA-1) and a hydrophilic copolymer belonging to (BBB-1) are particularly preferred.

In Japanese Patent Application (OPI) 89741/80 (corresponding to U.S. Patents 4,199,411 and 4,199,412), a mixture of cellulose acetate and polyethylene glycol is mentioned; however, polyethylene glycol is blended with cellulose acetate solely for purpose of improving storability of a coated layer. Such a purpose and effect is entirely different from the purpose and effect achieved by the present invention in which a coated layer is formed by blending at least two of specific polymers.

Monomers of Groups (A), (B) and (C) are described in greater detail below.

The ethylene-type monomers (A), hereafter Group (A) monomers, may also contain alkoxycarbonyl group, aryl groups and carbamoyl groups in addition to the above described carboxylic, sulfonic and phosphoric acid groups. Further, the above described acid groups may be linked directly to or may be linked through an atom (e.g., -O-) or an atomic group (e.g., -CH2-, -OCH2-) to the ethylene residue (moiety).

Specific examples of the Group (A) monomers include the following monofunctional monomers.

Acrylic acid, methacrylic acid, itaconic acid, maleic acid, monoalkyl itacontates (e.g., monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, etc.), monoalkyl maleates (e.g., monomethyl maleate, monoethyl maleate, monobutyl maleate, monooctyl maleate, etc.), citraconic acid, styrene-sulfonic acid, vinylbenzylsulfonic acid, vinylsulfonic acid, acryloyloxyalkylsulfonic acids (e.g., acryloyloxymethylsulfonic acid, acryloyloxyethylsulfonic acid, acryloyloxypropylsulfonic acid, acryloyloxybutylsulfonic acid, etc.), methacryloyloxyalkylsulfonic acids (e.g., methacryloyloxymethylsulfonic acid, methacryloyloxyethylsulfonic acid, methacryloyloxypropylsulfonic acid, methacryloyloxybutylsulfonic acid, etc.), acrylamidoalkylsulfonic acids (e.g., 2-acrylamido 2-methylethanesulfonic acid, 2-acryla mido-2-methylpropanesulfonic acid, 2-acrylamido-2-methyl- butanesulfonic acid, etc.), methacrylamidoalkylsulfonic acids (e.g., 2-methacrylamido-2-methylethanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylbutanesulfonic acid, etc.), acryloyloxyalkylphosphonates (e.g., acryloyloxyethylphosphonate, 3-acryloyloxypropyl-2-phosophonate, etc.), methacryloyloxyalkylphosphonates (e.g., methacryloyloxyethylphosphonate, 3-methacryloyloxypropyl-2-phosphonate, etc.), etc.

In the above described monomers of Group (A), the alkyl moiety generally has about 1 to about 8 carbon atoms. These acids representative of monomers of Group (A), ethylene-type monomers containing a carboxylic acid group, a sulfonic acid group or a phosphoric acid group may also be in the form of the alkali metal salts thereof (preferably Na+ or K+) or the ammonium salts thereof.

Examples of suitable aliphatic groups represented by R1 to R3 in formula (IB), hereafter often Group (B) monomers, include straight or branched alkyl groups (including cyclic alkyl groups) and substituted alkyl groups. These alkyl groups or the alkyl moieties thereof preferably have 1 to 1 2 carbon atoms.

Examples of substituents in the substituted alkyl groups include an aryl group, an aryloxy group, a halogen atom, a cyano group, an acyl group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an amino group (including an amino group substituted with one or two alkyl groups and aryl groups), a hydroxy group, an alkoxy group, and a heterocyclic residue (e.g., a 5- or 6-membered ring, which may be unsaturated or saturated and which may be condensed with an aromatic ring and in which the hetero atom includes one or more of an oxygen atom, a nitrogen atom and a sulfur atom, etc.), etc.

Examples of suitable aryl groups represented by R' to R3 in formula (IB) include, of course, both unsubstituted and substituted phenyl and naphthyl groups. Examples of suitable substituents thereof include an alkyl group, in addition to the substituents described above with respect to the substituted alkyl group for R' to R3.

Examples of the monomers of Group (B) include monofunctional monomers such as acrylic acid esters, methacrylic acid esters, crotonic acid esters, vinyl esters, maleic acid diesters, fumaric acid diesters, itaconic acid diesters and styrenes, etc.

Further specific examples of these Group (B) monomers include monofunctional monomers such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, tert-octyl acrylate, 2-phenoxyethyl acrylate, 2-chloroethyl acrylate, 2-bromoethyl acrylate, 4-chlorobutyl acrylate, cyanoethyl acrylate, 2-acetoxyethyl acrylate, dimethylaminoethyl acrylate, benzyl acrylate, methoxybenzyl acrylate, 2-chlorocyclohexyl acrylate, cyclohexyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate, phenyl acrylate, 5-hydroxypentyl acrylate, 2,2dimethyl-3-hydroxypropyl acrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate, 2-ethoxye thyl acrylate, 2-isopropoxyethyl acrylate, 2-butoxyethyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate, 2-(2-butoxyethoxy)ethyl acrylate, -methoxypolyethylene glycol acrylate (mean polymerization degree of polyethylene glycol is about 9), 1 -bromo-2-methoxyethyl crylate, 1 , 1 -dichloro-2- ethoxyethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, amyl methacrylate, hexylmethacrylate, cyclohexyl methacrylate, benzyl methacrylate, chlorobenzyl methacrylate, octyl methacrylate, N-ethyl-N-phenylaminoethyl methacrylate, 2-(3-phenylpropyloxy)ethyl methacrylate, dimethylaminophenoxyethyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate, phenyl methacrylate, naphthyl methacrylate, 2-hydroxyethyl methacrylate, 3hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, triethyleneglycol monomethacrylate, dipropylene glycol monomethacrylate, 2-methoxyethyl methacrylate, 3-methoxybutyl methacrylate, 2-acetoxyethyl methacrylate, acetoacetoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-iso-propoxyethyl methacrylate, 2-butoxyethyl methacrylate 2-(2-methoxyethoxy)ethyl methacrylate, 2-(2-ethoxyethoxy)ethyl methacrylate, 2-(2-butoxyethoxy)ethyl methacrylate, -methoxypoly- ethylene glycol methacrylate (mean polymerizaton degree of polyethylene glycol is 6), vinyl acetate, vinyl propionate, vinyl isobutyiate, vinyl dimethylpropionate, vinyl ethyl butyrate, vinyl valerate, vinyl carproate, vinyl chloroacetate, vinyl dichloroacetate, vinyl methoxyacetate, vinyl butoxyacetate, vinyl phenylacetate, vinyl acetoacetate, vinyl lactate, vinyl-ss-phenylbutyrate, vinyl cyclohexylcarboxylate, vinyl benzoate, vinyl salicyclate, vinyl chlorobenzoate, vinyl tetrachlorobenzoate, vinyl naphthoate, styrene, methylstyrene, dimethylstyrene, trimthylstryrene, ethylstryrene, diethylstyrene, isopropylstyrene, butylstyrene, hexylstyrene, cyclohexylstyrene, decystyrene, benzylstyrene, chloromethylstryrene, trifluoromethylstyrene, ethoxymethylstyrene, acetoxymethylstyrene, methoxystyrene, 4-methoxy-3-methylst,1rene, dimethoxystyrene, chlorostyrene, dichlorostyrene, trichlorostyrene, tetrachlorostyrene, pentachlorostyrene, bromostyrene, dibromostryrene, iodostyrene, fluorostyrene, trifluorostyrene, 2-bromo-4-trifluoromethylstyrene, 4-fluoro-3trifluoromethylstryene, vinylbenzoic acid methyl ester, butyl crotonate, hexyl crotonate, glycerin monocrotonate, dimethyl itacontate, diethyl itaconate, dibutyl itaconate, diethyl maleate, dimethyl maleate, dibutyl maleate, diethyl fumarate, dihexyl fumarate, dibutyl fumarate, etc.

Examples of the monomers other than those of Group (A) and Group (B) and copolymerizable therewith, hereafter often Group (C) monomers, include the following compounds.

acrylamides: for example, methylacrlyamide, ethylacrylamide, propylacrylamide, isopropylacrylamide, butylacrylamide, tert-butylacrylamide, heptylacrylamide, tert-octylacrylamide, cyclohexylacrylaminde, benzylacrylamide, hydroxymethylacrylamide, methoxyethylacrylamide, dimethy laminoethylacrylamide, hydroxyethylacrylamide, phenylacrylamide, hydroxyphenylacrylamide, tolylacrylamide, naphthylacrylamide, dimethylacrylamide, diethylacrylamide, dibutylacrylamide, diisobutylacrylamide, N-( 1 , 1 -dimethyl-3-oxobutyl)acrylamide, methylbenzylacrylamide, benzyloxyethylacrylamide, ss-cycanoethylacrylamide, acryloylmorpholine, N-methyl-N-acryloylpiperazine, N-acryloylpiperid ine, N-( 1 , 1 -d imethyl-3-hydroxybutyl)acrylamide, N-ss-morpholinoethylacrylam- ide, N-acryloylhexamethyleneim ine, N-hydroxyethyl-N-methylacrylamide, N-2-acetamidoethyl-Nacetylacrylamide, acrylhydrazine, etc.

methacrylamides: for example, methylmethacrylamide, tert-butylmethacrylamide, tert-octylmethacrylamide, benzylmethacrylamide, cyclohexylmethacrylamide, phenylmethacrylamide, dimethylmethacrylamide, diethylmethacrylamide, dipropyimethacrylamide, hydroxyethyl-N-methylmethacrylamide, N-methyl-N-phenylmethacrylam ide, N-ethyl-N-phenylmetharylamide, methacrylhydrazine, etc.

allyl compounds: for example, ailyl acetate, allyl caproate, allyl caprylate, allyl laurate, allyl palmitate, allyl stearate, allyl benzoate, allyl acetoacetate, allyl lactate, allyloxyethanol, allyl butyl ether, allyl phenyl ether, etc.

vinyl ethers: for example, methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, octyl vinyl ether, decyl vinyl ether, ethylhexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethylvinyl ether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinyl ether, hydroxyethylvinyl ether, diethylene glycol vinyl ether, dimethylaminoethyl vinyl ether, etc.; vinyl ketones: for example, methyl vinyl ketone, phenyl vinyl ketone, methoxyethyl vinyl ketone, etc.; olefins: for example, unsaturated hydrocarbons such as dicyclopentadiene, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl- 1 -pentene, 1-heptene, 1-octene, 1-decene, 5 methyl-l-nonene, 5,5- d imethyl- 1 -octene, 4-methyl-1-hexene, 4,4-d imethyl- 1 -pentene, 5-methyl 1-hexene, 4-methyl-l-heptene, 5-methyl- 1 -heptene, 4, 4-dimethyl- 1 -hexene, 5,5, 6-trimthyl-1 - heptene, 1-dodecene, 1-octadecene, etc.; ; vinyl heterocyclic compounds (where the heterocyclic ring may be a 5- or 6-member ring, which may be condensed with an aromatic ring and in which the hetero atoms include one or more of a nitrogen atom, an oxygen atom anda sulfur atom): for example, N-vinyloxazolidone, vinylpyridine, vinyl picoline, N-vinylimidazole, N-vinyl-2-methylimidazole, N-vinyltriazole, N-vinyl3, 5-dimethyltriazole, N-vinylpyrrolidone, N-vinyl-3, 5-dimethylpyrazole, N-vinylcarbazole, vinylthiophene, N-vinylsuccinimide, N-vinylgiutarimide, N-vinyladipimide, N-vinylpiperidone, N-vinyl-e caprolactam, N-vinyl-2-pyrrolidone, etc.; unsaturated nitriles: for example, acrylonitrile, methacrylontrile, etc.; polyfunctional monomers: for example, polyfunctional monomers having a plurality of vinyl groups (for example, 2 to 3 vinyl groups), e.g., aliphatic or aromatic hydrocarbons having a plurality of vinyl groups (such as butadiene and divinylbenzene), bis- or tris-a,ss-unsaturated carbonyl compounds (for example, diallyl phthalate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate and compounds having the following formulae:

and polyfunctional monomers having a vinyl group andan active methylene group (for example, acetoacetoxyethyl methacrylate described in Japanese Patent Application (OPI) 5819/70, etc.), etc.

Of these monomers, acrylic acid, methacrylic acid, itaconic acid, 2-acrylamido-2-methylpropaneslfonic acid and phosphoric acid esters having polymerizable unsaturared functional groups as described above (but having a free phosphoric acid group of a salt thereof) are preferred as the monomers of Group (A), and acrylic acid is most preferred. Acrylic acid esters, methacylic acid esters and stryenes are preferred as monomers of Group (B), and butyl acylate and styrene are most preferred.

Of the monomers of Group (C), acrylamides and methacrylamides are preferred and, acrylamides or methacrylamides shown by formula (IID) hereinafter are particularly preferred.

The ratio of Group (A) monomer and Group (B) monomer or Group (A) monomer, Group (B) monomer and Group (C) monomer components in the copolymers of the polymer latex can be appropriately varied depending upon the characteristics desired for electrodes for measuring halogen ions to which a coated layer formed using the polymer latex is applied. A preferred amount of the Group (A) monomer component is in the range of about 0.1 x 10-3 mol to about 2.2 X 10-3 mol per gram of the solid content of the latex polymer. A particularly preferred amount of the Group (A) monomer component is in the range of 0.4 x 10-3 mol to 1.0 X 10-3 mol per gram of the solid content of the latex polymer. A preferred amount of the Group (B) monomer component is in the range of about 50 to about 99% by weight based on the solid content of the polymer latex and particularly 80 to 99% by weight.A preferred amount of the Group (C) monomer component is in the range of O to about 49% by weight and particularly 0 to 19% by weight of the solid content of the polymer latex. A suitable molcular weight for the polymer latex is about 5,000 to about 100,000, preferably 20,000 to 50,000.

The ratio of the above described monomer components is based on the relative ratio of monomers added to a polymerization reactor in the conventional free radical polymerization process.

Typical examples of preferred latex polymers composing the coated layer provided in the present invention include the following compounds, but the present invention is not to be construed as being limited to these examples.

(1) Ethyl methacrylate-acrylic acid copolymer (97:3 by weight, hereafter the same) (2) Propyl methacrylate-acrylic acid copolymer (96:4) (3) Butyl methacrylate-acrylic acid copolymer ((97.5:2.5) (4) Butyl methacrylate-acrylic acid copolymer (96:4) (5) sec-Butyl methacrylate-acrylic acid copolymer ((97:3) (6) tert-Butyl methacrylate-acrylic acid copolymer (98:2) (7) Ethyl methacrylate-itaconic acid copolymer (98:2) (8) Butyl methacrylate-itaconic acid copolymer (97.5:2.5) (9) Cyclohexyl methacrylate-acrylic acid copolymer (97:3) (10) Tetrahydrofurfuryl methacry!ate-acrylic acid copolymer (96:4) (11) 2-Acetoxyethyl methacrylate-acrylic acid copolymer (97:3) (12) Ethyl acrylate-methacrylic acid copolymer ((90: 10) (13) Benzyl acrylate-acrylic acid copolymer ((96:4) (14) Phenyl acrylate-acrylic acid copolymer (97:3) (15) Propyl methacrylate-maleic acid copolymer (99:1) (16) Butyl methacrylate-sodium vinylbenzylsulfonate copolymer (91:9) (17) Ethyl acrylate-2-acrylamido-2-methylpropanesulfonic acid copolymer (93:7) (18) Propyl acrylate-sodiu m 2-methacryloyloxyethylsulfonate copolymer (92:8) (19) Butyl methacrylate-monoethyl itaconate copolymer (93:7) (20) sec-Butyl methacrylate-2-methacryloyloxyethyl phosphonate copolymer (91:9) (21) Styrene-butyl acrylate-acrylic acid copolymer ((53.4:43.6:3) (22) Styrene-butyl acrylate-acrylic acid copolymer (52.8:43.2:4) (23) Styrene-ethoxyethyl acrylate-acrylic acid copolymer (48:48:4) (24) Styrene-butyl acrylate-itaconic acid copolymer (48:48::4) (25) Styrene-butyl acrylate-methacr)-iic acid copolymer (46:46:8) (26) Styrene-ethyl acrylate-2-acrylamido-2-methyl propanesulfonic acid copolymer ((40:50:10) (27) Methyl methacrylate-butyl methacrylate-itaconic acid copolymer (10:85:5) (28) Cyclohexyl methacrylate-octyl acrylate-acrylic acid copolymer (70:24:6) (29) Benzyl methacrylate-2-ethylhexyl acrylate-acrylic acid copolymer (60:35:5) (30) Phenyl methacrylate-butyl acrylate-sodium 2-methacryloyoxyethylsulfonate copolymer (55:40:5) (31) Ethyl methacrylate-2-acetoxyethyl methacrylate-acrylic acid copolymer (30:64:6) (32) Butyl methacrylate-2-hydroxyethyl methacrylate copolymer (90:5:5) (33) Butyl methacrylate-acrylic acid-2-acrylyamide-2-methylpropanesulfonic acid copolymer (92:4::4) (34) Benzyl methacrylate-vinyl acetate-sodium 2-methacryloyloxypropanesulfonate (30:63:7) (35) Ethyl methacrylate-vinyl butylate-acrylic acid copolymer (60:36:4) (36) Vinyltoluene-ethoxyethyl acrylate-acrylic acid copolymer (53:43:4) (37) Styrene-dibutyl maleate-maleic acid copolymer (50:43:7) (38) Butyl methacrylate-dimethylacrylamide-acrylic acid copolymer (70:25:5) (39) Cyclohexyl methacrylate-N-( 1 , 1 -dimethyl-3-oxo-butyl)acrylamide-acrylic acid copolymer (60:36:4) (40) Butyl methacrylate-tert-butylacrylamide-acryl ic acid copolymer (70:26:4) (41) Butyl methacrylate-acrylonitrile-methacrylic acid copolymer (80:12:8) (42) Butyl methacrylate-ethylene glycol dimethacrylate-acrylic acid copolymer (92:3: :5) (43) Styrene-butyl acrylate-divinylbenzene-acrylic acid copolymer (50:42:3:5) (44) Tetrahydrofurfuryl methacrylate-ethyl acrylate-ethylene glycol dimethacrylate-itaconic acid copolymer (60:32:4:4) (45) H exyl methacrylate-tert-butylacryla mide-methylene bisacrylamide-2-acrylamide-2-methylpropane-sulfonic acid copolymer (62:26:3:9) These polymer latexes can be employed by blending two or more thereof, for purpose of improving film-formjng ability or planability, or other physical and mechanical properties.

The polymer latex used in the present invention can be synthesized using processes well known to one skilled in the art of synthesizing polymers. The polymer latex can be easily synthesized with reference to the descriptions appearing hereafter in the present specification and in, e.g., U.S. Patents 2,914,499, 3,033,833 and 3,547,899, etc. Representative examples of such syntheses are shown in Japanese Patent Application (OPI) 72622/78 (corresponding to U.S. Patent 4,199,362), etc.

Synthesis examples of typical polymer latexes can be advantageously employed for the coated layer are given below.

Synthesis Example 1 Synthesis of Latex Polymer (3): A 1 liter 3-neck flask equipped with a thermometer, a nitrogen inlet conduit, a stirrer, a reflux condenser and a dropping funnel was placed on a steam bath. 5 g of sodium nonyiphenoxy polyethylene propanesulfonate ether was put in this flask and 300 ml of distilled water was then added thereto to dissolve. 70 g of n-butyl methacrylate was added to the mixture to emulsify the mixture. 1.868 g of potassium persulfate and 0.75 g of sodium hydrogen sulfite were dissolved in 100 ml of distilled water. One-third of the resulting solution (Solution A) was put in the flask. The air in the flask was purged with nitrogen gas. The temperature in the flask was increased to 60"C and stirring was continued. A polymerization reaction began with the generation of heat.After the generation of heat reached a maximum, 1/4 of the remaineder of Solution A was added to the reaction mixture. A mixture of 27.5 g of n-butyl methacrylate and 2.5 g of acrylic acid was added dropwise using a dropping funnel and the addition thereof was completed after 30 minutes. The temperature in the flask was kept at 60"C during the addition.

After completion of the addition, 1/2 of the remainder of Solution A was added to the mixture after the lapse of 1 hour. After 30 minutes, the remainder of Solution A was added to the mixture. After stirring for 1 hour at 60"C, the temperature was decreased to room temperature (about 20 to 30"C) to finish the reaction.

Synthesis Example 2 Synthesis of Latex Polymer (4): 5 g of sodium nonylphenoxy polyoxyethylene propane-sulfonate ether was placed into the same type of apparatus as described in Synthesis Example 1, and dissolved using 300 ml of distilled water. After purging the air in the flask with nitrogen gas, a mixture of 96 g of n-butyl methacrylate and 4 9 of acrylic acid was added thereto and an emulsion was formed. 1.975 g of potassium persulfate and 0.761 of sodium hydrogen sulfite were dissolved in 100 ml of distilled water (Solution A2). 1/2 of Solution A2 was put in the flask. When the temperature in the flask had risen to 60"C, a polymerization reaction began with the generation of heat. Stirring was continued while the temperature in the flask was kept at 60"C by reducing the temperature of the steam bath.After 2 hrs., 1/2 of the remainder of Solution A2 was added to the mixture.

After 30 mins., the remainder of Solution A2 was added thereto. After the stirring had been continued at 60"C for 1 hr., the temperature was decreased to room temperature to finish the reaction.

Synthesis Example 3 Synthesis of Latex Polymer (21): A 2 liter 3-neck flask equipped with a thermometer, a nitrogen inlet tube, a stirrer, a reflux condenser and a dropping funnel was placed on a steam bath. 10 g of sodium nonylphenoxy polyoxyethylene propanesulfonate ether was put in this flask and 600 ml of distilled water was added thereto to dissolve. The air in the flask was purged with nitrogen gas, a mixture of 87.3 g of n-butyl acrylate, 6 g of acrylic acid and 106.7 g of styrene was added thereto and an emulsion was formed. 4.836 g of potassium persulfate and 1.862 g of sodium hydrogen sulfite were dissolved in 200 ml of distilled water (Solution A3). 1/2 of Solution A3 was put in the flask. When the temperature in the flask had increased to 60"C, a polymerization reaction began with generation of heat.Stirring was continued while the temperature in the flask was kept at 60"C by reducing the temperature of the steam bath. After 2 hrs., 1 /2 of the remainder of Solution A3 was added to the mixture. After 30 mins., the remainder of Solution A3 was added thereto. After the stirring had been continued at 60"C for 1 hr., the temperature was reduced to room temperature to finish the reaction.

Synthesis Example 4 Synthesis of Latex Polymer (22): The synthesis was carried out in the same manner as in SYnthesis Example 3 except that the amounts of styrene, n-butyl acrylate and acrylic acid were each 105.6 g, 86.4 g and 8 g, respectively and a solution prepared by dissolving 4.864 g of potassium persulfate and 1.874 9 of sodium hydrogen sulfite in 200 ml of distilled water (Solution A4) was used instead of Solution A3.

Synthesis Example 5 Synthesis of Latex Polymer (24): 5 g of sodium nonylphenoxy polyoxyethylene propane-sulfonate ether was placed in the same type of apparatus as described in Synthesis Example 1, and dissolved by adding 300 ml of distilled water. After purging the air in the flask with nitrogen gas, 48 9 of n-butyl acrylate, 48 g of styrene and 4 g of itaconic acid were added to the flask and the mixture was emulsified.

2.342 g of potassium persulfate and 0.902 g of sodium hydrogen sulfite were dissolved in 100 ml of distilled water (Solution As). 1/2 of Solution A5 was put in the flask. When the temperature in the flask was increased to 60"C, a polymerization reaction began with the generation of heat. The stirring was continued while the temperature in the flask was kept to 60"C by reducing the temperature of the steam bath. After 2 hrs., 1/2 of the remainder of Solution As was added to the mixture. After 30 mins., the remainer of Solution As was added thereto. After the stirring had been continued at 60"C for 1 hr., the temperature was reduced to room temperature to finish the reaction.

II. Polymer Latex (all): Polymer latex produced by emulsion polymerization of each of at least one monomer selected from the group consisting of monomers of Group (D), at least one monomer selected from the group consisting of monomers of Group (E) and at least one monomer selected from the group consisting of monomers of Group (F) Group (D): Monomers represented by the following formula (IID) (a suitable amount is in the ragne of about 0.5 to about 40% by weight):

wherein R4 represents a hydrogen atom or a methyl group; T represents a hydrogen atom or an aliphatic group; Q represents a -CH2-OCOR group, a

group, a -CH2OR2d group, a

group or a

group.

R" represents an aliphatic group or an aryl group; Ria and R'b, which may be the same or different, each represents an aliphatic group or R'" and Rib may combine to form a ring; R2d represents a hydrogen atom or an aliphatic group; R3d, R4d, R5d, R6d and R7d, which may be the same of different, each represents a hydrogen atom or a CH2OR2d group provided that all of the R3d to R7d do not represent hydrogen atoms at the same time; and W represents an atomic group necessary to form a ring together with the -N-CO- linkage.

Group (E): Polymerizable ethylenically unsaturated monomers having at least a free carboxylic acid group, sulfonic acid group or phosphoric acid group or a salt thereof: Group (F): Monomers other than those monomers of Group (A) and Group (B) which are copolymerizable with the monomers of Group (D) and Group (E): In the polymer latex (II) used in the present invention, a suitable amount of the Group (D) monomer is about 0.5 to about 40% by weight, preferably 2 to 21% by weight, a suitable amount of the Group (E) monomer is about 1 to about 12% by weight, preferably 2 to 8% by weight, and a suitable amount of the Group (F) monomer is about 48 to about 99% by weight, preferably 77 to 96% by weight. Monomers of Groups (D), (E) and (F) are illustrated in greater detail below.Throughout this specification the monomer compositions (% by weight) are for the latex prior to emulsion polymerization.

The aliphatic group for R" in formula (IID) may contain 1 to 8 carbon atoms and includes a straight or branched chain substituted or unsubstituted alkyl group having 1 to 8 carbon atoms and preferably 1 to 4 carbon atoms (e.g., methyl, ethyl, t-butyl, chloromethyl, etc.).

The aliphatic group for R1a and Rlb includes a straight or branched alkyl group having 1 to 6 carbon atoms and preferably 1 to 3 carbon atoms and may be substituted or unsubstituted (e.g., methyl, ethyl, propyl, etc.). Examples of the substituents for the alkyl group include a hydroxy group, a halogen atom, a straight or branched alkoxy group having 1 to 6 carbon atoms, etc.

The ring formed by R1" and Rib may be a 5-membered or 6-membered saturated or unsaturated heterocyclic ring formed with the nitrogen atom in the -CH2NR1aRlb moiety and may contain one or more other hetero atoms such as a nitrogen atom, a sulfur atom or an oxygen atom.

The aliphatic groups for T and R2d include a straight, branched or cyclic alkyl group having 1 to 1 8 carbon atoms and preferably 1 to 6 carbon atoms which may be substituted or unsubstituted. Examples of the substituents include a monocyclic aryl group having 6 to 10 carbon atoms such as a phenyl group, a halogen atom such as fluorine, chlorine, bromine or iodine, etc.

The aliphatic groups for T and R2d also include an alkenyl group having 2 to 1 8 carbon atoms and preferably 2 to 6 carbon atoms, such as an allyl group, an ethenyl group, a butenyl group, an oleyl group, etc.

Specific examples of the alkyl groups for T or R2d include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, etc.

Examples of the atomic group represented by W include, for example, a -(CH2)3- group or a -(CH2)5- group, etc., forming a 5- to 7-membered ring.

When Q is a

group, Q represents a methylol product of a diacetoneacrylamide or a diacetone methacrylamide or a precursor thereof. The methylol product includes a mono-, di-, tri-, tetra- or penta-methylol product. For example, the trimethylol product is a mixture including substituted products in which the degree of the substitution is 3 in which the positons substituted are different as a main component and further contains methylol products in which the degree of the substitution is 1, 2, 4 or 5, and which has an average degree of methylolation of about 3.

Specific examples of compounds represented by formula (IID) include N-hydroxymethylacrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, N-tert-butoxymethylacrylamide, N-butoxymethylacrylamide, N-hydroxymethylmethacrylamide, N-methoxymethylmethacrylamide, N-ethoxymethylmethacrylamide, N-butoxymethylmethacrylamide, hydroxymethylated diacetoneacrylamide having a hydroxymethylation degree of about 0.5 to about 4.5 and; acrylamide ormethacrylamide derivatives such as N-(N', N '-dimethylaminomethyl)methacrylamide, N-(N',N'dibutylaminomethyl)methacrylamide, N-(morpholinomethyl)methacrylamide, N-(N'-methyl-N'-(2hydroxyethyl)-amino)methyl methacrylamide, N-(N ', N'-bis(2-hydroxyethyl)-amino)methyl methacrylamide, N-acetoxymethylacrylamide, N-propyloxymethylacrylamide, N-acryiamidomethylpyrro- lidone, etc. and other acrylamide or methacrylamide derivatives as described in Macromoleculare Chemie, vol. 57, pages 27 to 51 (1962), etc.

Of the monomers of Group (E), an unsaturated acid represented by the following general formula (IIIE) or a salt thereof is preferred:

wherein R8e represents a hydrogen atom or a methyl group; L and M, which may be the same or different, each represents a hydrogen atom, a carboxy group, a carboxyalkylene group (an alkylene moiety having 1 to 3 carbon atoms is preferred), an alkoxycarbonyl group (the alkyl moiety has preferably 1 to 8 carbon atoms and may be a straight, branched or alicyclic Ikyl group), or a -COO-R'-OPO3H2 group (wherein R' represents a straight or branched alkylene group and those alkylene groups having 1 to 1 2 carbon atoms are preferred).

Also L and M may represent a group in which the carboxy group, the carboxyalkylene group or the -COO-R'-OPO3H2 group and an alkali metal ion (preferably Na+ or K+) or ammonium ion form a salt. Further, at least one of L and M should be a carboxy group, a carobxyalkylene group, a -COO-R'-OPO3H2 group or a salt thereof (as described above).

Specific examples of the monomers represented by formula (IIIE) include the following: acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, monoalkyl itaconates (for example, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, etc.), monoalkyl maleates (for example, monomethyl maleate, monoethyl maleate, monobutyl maleate, monooctyl maleate, etc.), citraconic acid, sodium acrylate, ammonium acrylate, ammonium methacrylate, acryloyloxyalkylphosphates (for example, acryloyloxyethyl phosphate, 3-acryloyloxypropyl-2phosphate, etc.), methacryloyloxyalkyl phosphates (for example, methacryloyloxyethyl phosphate (acid phosphoxyethyl methacrylate), 3-methacryloyloxypropyl-2-phosphate, etc.), 3-chloro-2-acid phosphoxypropyl methacrylate.

Although the monomers of Group (F) may be any of a wide variety of ethylenically unsaturated monomers which are known in the art, a monomer represented by the following general formula (IVF) is particularly effective:

wherein X' represents a hydrogen atom, a methyl group or a -COOR1 group; Y' represents a hydrogen atom, a methyl group or a (CH2)n,-COOR' ' group; I represents an aryl group, a -COOR"' group, a cyano group, a halogen atom or a -OCO-R"' group; R9', R'O' and R"f, which may be the same or different, each represents an aliphatic group or an aryl group; and nf represents 0, 1, 2 or 3.

The aliphatic group for 99' to R'1' includes a straight, branched or cyclic alkyl group which may be substituted or unsubstituted. The alkyl group preferably has 1 to 12 carbon atoms.

Examples of the substituents for the substituted alkyl group include an alkoxy group having 1 to 8 carbon atoms such as methoxy, ethoxy, isopropoxy, butoxy, etc.; an aryl group having 6 to 10 carbon atoms such as phenyl, chlorophenyl, dimethylphenyl, etc., an aryloxy group having 6 to 10 carbon atoms such as phenoxy, chlorophenoxy, etc., an arylalkyleneoxy group having 7 to 1 2 carbon atoms such as benzyloxy, phenethyloxy, etc., a halogen atom, a cyano group, an acyl group having 2 to 8 carbon atoms such as acetyl, propionyl, etc., an alkylcarbonyloxy group having 2 to 8 carbon atoms such as acetoxy, propionyloxy, caproyloxy, etc., a caproyloxy, etc., an arylcarbonyloxy group having 7 to 1 2 carbon atoms such as benzoyloxy, chlorobenzoyloxy, etc., an amino group (including a substituted amino group in which the substituents may be an alkyl group, an aryl group, etc., and the number of the substituents is 1 or 2), a hydroxy group, an alkoxyalkyleneoxy group having 3 to 10 carbon atoms such as methoxyethoxy, ethoxyethoxy, butoxyethoxy, etc., a heterocyclic residue (wherein the hetero atom is, e.g., an oxygen atom, a nitrogen atom, a sulfur atom, etc., a 5- or 6-membered ring being preferred, and the ring may be unsaturated or saturated and condensed with an aromatic ring, etc.).

Further, the aryl group for R9' to R11 includes a substituted or unsubstituted phenyl or naphthyl group. Examples of the substituents include an alkyl group in addition to the substituents described above for the substituted alkyl group.

Examples of the monomers of Group (F) include monomers such as acrylic acid esters, methacrylic acid esters, crotonic acid esters, vinyl esters, maleic acid diesters, fumaric acid diesters, itaconic acid diesters, styrenes, acrylonitriles, vinyl chloride, etc., wherein the alcoholderived moiety contains 1 to 24 carbon atoms.

Further, specific examples of these Group (F) monomers include acrylic acid esters, e.g., methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, amyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, 2-octyl acrylate, tert-octyl acrylate, 2-phenoxyethyl acrylate, 2-chloroethyl acrylate, 2-bromoethyl acrylate, 4chlorobutyl acrylate, cyanoethyl acrylate, 2-acetoxyethyl acrylate, dimethylaminoethyl acrylate, benzyl acrylate, methoxybenzyl acrylate, 2-ch lorocyclohexyl acrylate, 2-chlorohexyl acrylate, cyclohexyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate, phenyl acrylate, 5-hydroxypentyl acrylate, 2,2-dimethyl-3-hydroxypropyiacrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate, 2-ethoxyethyl acrylate, 2-iso-propoxyethyl acrylate, 2-butoxyethyl acrylate, 2-(2-methoxyethoxy)ethyl acrylate, 2-(2-butoxyethoxy)ethyl acrylate, 1 -bromo-2-methoxyethyl acrylate, 1 , 1- di-chloro-2-ethoxyethyl acrylate, etc.; methacrylic acid esters, e.g., methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, sec-butylmethacrylate, amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, chlorobenzyl methacrylate, octyl methacrylate, N-ethyl-N-phenylaminoethyl methacrylate, 2-(3-phenylpropyloxy)ethyl methacrylate, furfuryl methacrylate, tetrahydrofurfuryl methacrylate, phenyl methacrylate, cresyl methacrylate, naphthyl methacrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, triethylene glycol monomethacrylate, 2-methoxyethyl methacrylate, 3-methoxybutyl methacrylate, 2-acetoxyethyl methacrylate, acetoacetoxyethyl methacrylate, 2-ethoxyethyl methacrylate, 2-iso-propoxyethyl methacrylate, 2-butoxyethyl methacrylate, 2-(2-methoxyethoxy)ethyl methacrylate, 2-(2-ethoxyethoxy)ethyl methacrylate, 2-(2-butoxyethoxy)ethyl methacrylate, etc.; vinyl esters, e.g., vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl dimethylpropionate, vinyl ethylbutyrate, vinyl valerate, vinyl caproate, vinyl chloroacetate, vinyl dichloroacetate, vinyl methoxyacetate, vinyl butoxyacetate, vinyl phenylacetate, vinyl acetoacetate, vinyl lactate, vinyl fi-phenylbutyrate, vinyl cyclohexylcarboxylate, vinyl benzoate, vinyl salicylate, vinyl chlorobenzoate, vinyl tetrachlorobenzoate, vinyl naphthoate, etc.; styrenes, e.g., styrene, methylstryrene, dimethylstyrene, trimethylstryrene, ethylstryrene, diethylstyrene, isopropylstryrene, butylstryrene, hexylstyrene, cyclohexylstyrene, decylstryrene, benzylstyrene, chloromethylstyrene, trifluoromethylstryrene, ethoxymethylstryrene, acetoxymethylstyrene, methoxystyrene, 4-methoxy-3-methylstryrene, dimethoxystyrene, chlorostyrene, dichlorostyrene, trichlorostyrene, tetrachlorostyrene, pentachlorostyrene, bromostyrene, dibromostyrene, fluorostyrene, trifluornstyrene, 2-bromo-4trifluoromethylstyrene, 4-fluoro-3-trifluoromethylstyrene, vi nylbenzoic acid methyl ester, etc.; crotonic acid esters, e.g., butyl crotonate, hexyl crotonate, glycerin monocrotonate, etc; itaconic acid diesters, e.g., dimethyl itaconate, diethyl itaconate, dibutyl itaconate, etc.; maleic acid diesters, e.g., diethyl maleate, diethyl maleate, dibutyl maleate, etc.; fumaric acid diesters, e.g., diethyl fumarate, dihexyl fumarate, dibutyl fumarate, etc.

Preferred Composition of the Copolymer: As a monomer (D), about 0.5 to about 40% by weight of N-hydroxymethyl acrylamide or Nhydroxymethyl methacrylamide, more preferably an N-alkoxymethyl acrylamide or an N-alkoxymethyl methacrylamide: as monomer (E), about 1 to about 12% by weight, more preferably about 2 to about 8% by weight of acrylic acid, methacrylic acid or itaconic acid: and as monomer (F), about 48 to about 99% by weight, more preferably about 77 to about 98% by weight of at least one ethylenically unsaturated monomer represented by the above described general formula (IVF).

As monomer (F), two or more copolymerizable components can be used, if desired. For example, in order to obtain a latex having an appropriate minimum film forming temperature (described in detail hereinafter), a hard component and a soft component can be used in an appropriate ratio. In this case, a hard component is an ethylene type monomer of the general formula (IVF) which forms a homopolymer having a glass transition temperature of 50"C or more, for example, styrene, acrylonitrile or methyl methacrylate is preferred.On the other hand, soft component is an ethylene type monomer of the general formula (IVF) which forms a homopolymer having a glass transition temperature of 40"C or less, for example, a substituted or unsubstituted alkyl acrylate (examples of the substituents include an alkoxy group, a halogen atom, etc.) is preferred.

Typical examples of preferred copolymers of aqueous latexes which can be employed to form the coated layer in accordance with the present invention are illustrated below.

(46) Styrene-butyl acrylate-acrylic acid-N-hydroxymethyl acrylamide copolymer (50:40:3:7 by weight ratio, hereafter the same) (47) Styrene-butyl acrylate-acrylic acid-N-hydroxymethlacrylamide copolymer (61:27:4:8) (48) Methyl methacrylate-butyl acrylate-acrylic acid-N-hydroxymethyl acrylamide copolymer (32:58:4:6) (49) Methyl methacrylate-butyl acrylate-acrylic acid-N-hydroxymethylacrylamide copolymer (63:28:3:6) (50) Methyl methacrylate-acrylic acid-N-hydroxymethyl acrylamide copolymer (92:4:4) (51) Butyl methacrylate-acrylic acid-N-hydroxymethyl acrylamide copolymer (90:4:6) (52) sec-butyl methacrylate-acrylic acid-N-butoxymethyl acrylamide copolymer (77:3:20) (53) Ethyl methacrylate-itaconic acid-hydroxymethylated diacetone acrylamide (degree of hydroxymethylation, 2.5) copolymer (95:2.5::2.5) (54) 2-Acetoxyethyl methacrylate-acrylic acid-N-ethoxymethyl acrylamide (87:3:10) (55) Ethyl acrylate-methacrylic acid-N-butoxymethyl acrylamide copolymer (88:6:6) (56) Propyl methacrylate-maleic acid-N-methoxy-methyl acrylamide copolymer (90:2:8) (57) Styrene-butyl acrylate-2-methacryloyloxyethyl phosphate-N-butoxymethyl acrylamide copolymer (50:40:2:8) (58) Styrene-ethoxyethyl acrylate-acrylic acid-N-hydroxymethyl acrylamide copolymer (43:43:4: 10) (59) Styrene-propyl acrylate-itaconic acid-N-methoxymethyl methacrylamide copolymer (40:38:8: 14) (60) Styrene-butyl acrylate-acrylic acid-hydroxymethylated d jacetone acrylamide (degree of hydroxymethylation, 2.5) copolymer (51.7:41.8:2:4.5) (61) Methyl methacrylate-butyl acrylate-acrylic acid-N-hydroxymethyl acrylamide copolymer (36.1:53.9:2:8) (62) n-Butyl methacrylate-acrylonitrile-acrylic acid-N-ethoxymethyl acrylamide copolymer (78:6:4: 12) (63) n-Butyl methacrylate-acrylonitrile-itaconic acid-N-hydroxymethyl methacrylamide copolymer ((79:5:2: 14) (64) Styrene-n-butyl acrylate-acrylic acid-N-acetoxymethyl acrylamide copolymer (50:40:3:7) (65) Styrene-n-butyl acrylate-acrylic acid-N-(morpholinomethyl)methacrylamide copolymer (48:40:4:8) All ratios in the above examples are by weight and based on the amount of each monomer added in a synthesis of the polymer latex (II).

The polymer latex (II) used in the present invention can be synthesized advantageously in a conventional manner with reference to the descriptions appearing in, for example, Japanese Patent Publications 29195/72. Japanese Patent Applications (OPI) 37488/73, 76593/73, 92022/73,21134/74 and 120634/74; Japanese Patent Application (OPI) 148589/76; British Patents 1,211,039 and 961,395, U.S. Patents 3,847,615, 3,840,371, 3,963,495, 2,795,564, 2,914,499, 3,033,833, 3,547,899, 3,227,672, 3,290,417, 3,262,919, 3,245,932, 2,681,897 and 3,230,275, Canadian Patent 704,778, John C.Petropoulos et al, OFFICIAL DIGEST, vol. 33, pages 719 to 736 (1961), Sadao Hayashi, Emulsion Nyumon (Introduction of Emulsion) (1970), Souichi Muroi, Chemistry of PolymerLatex (1 970), Takuhiko Motoyama, Vinyl Emulsion (1965) and Mike Shider Juang et al, Journal of Polymer Science, Polymer Science Edition, vol. 14, pages 2089 to 2107 (1976). Needless to say, the polymerizaton initiatior, concentration of reactants, the polymerization temperature, reaction time and the like can be varied widely in accordance with the effect desired.For example, the polymerization is, in general, carried out at 20 to 180"C, preferably 40 to 120"C, using 0.05 to 5% by weight of a free radical polymerization initiator and 0.1 to 10% by weight of an emulsifier based on the amount of monomers to be polymerized.

Suitable polymerization initiators include azo compounds, peroxides, hydroperoxides, redox catalysts, etc., for example, potassium persulfate, ammonium persulfate, tertbutyl peroctoate, benzoyl peroxide, isopropyl percarbonate, 2,4-dichlorobenzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroxide, dicumyl peroxide, azobis(2-amidinopropane)-hydrochloride, and the like.

Suitable emulsifiers include anionic, cationic, amphoteric or nonionic surface active agents and water-soluble polymers, for example, sodium laurate, sodium dodecylsulfate, sodium 1 octoxyCarbonylmethyl-1-ocotoxycarbonylmethanesulfonate, sodium laurylnaphthalenesulfonate, sodium laurylbenzenesulfonate, sodium laurylphosphate, cetyltrimethylammonium chloride, N-2ethylhexypyridinium chloride, polyoxyethylene nonyl phenyl ether, polyoxyethylene sobritanlauryl ester, polyvinyl alcohol, water-soluble polymers, emulsifiers described in Japanese Patent Publication 6190/78, and the like.

These polymer latexes of Group II can also be used as a blend of two or more. Further, the polymer latexes of Group II can also be employed as a blend with the polymer latex of Group The average particle size of the polymer latexes (I) and (II) described above is preferably about 0.05 to about 0.4 ym and particularly about 0.05 to about 0.2 ym. The average particle size is the number mean of the diameter of the particles measured microscopically in a conventional manner.

Further, latexes of polyvinyl chloride, latexes as described in U.S. Patent 2,795,564 and Japanese Patent Application (OPI) 22935/74, and other latexes that are easily conceivable to one skilled in the art in polymer chemistry can suitably be employed.

Some of latexes have poor property for forming a coated layer; however, by blending these latexes with a latex(es) having good property for forming a coated layer, not only capability of forming a layer but also efficiencies are improved.

It is necessary to incorporate a surface active agent for forming a latex. The incorporation of a surface active agent is also preferred for coating; for example, a fluorine type surface active agent is preferably employed.

Blending with a hydrophilic polymer is also effective for improving efficiencies of a coated layer, depending upon occasion. As hydrophilic polymers, hydrophilic polymers known for photographic use are preferably used.

Representative hydrophiclic polymers are those o-obtained by polymerizing at least one of monomers represented by formula:

wherein P represents a hydrogen atom or an alkyl group; Q represents a

nucleus (wherein Z represents an atomic group necessary for completing a pyrrolidone nucleus, an imidazole nucleus, an oxazolone nucleus or a succinimido nucleus), a 2-pyridyl group, a 4pyridyl group, a hydroxycarbonyl group, an aminocarbonyi group, an alkylaminocarbonyl group, a substituted alkylaminocarbonyl group, a dialkylaminocarbonyl group, a substituted dialkylaminocarbonyl group, a sulfonyl group, a hydroxy group, an amino group, a substituted amino group, a carboxyaryl group, a sulfoaryl group, a hydroxyethoxycarbonyl group, a sulfonic acid group, a phosphoric acid group, a substituted alkoxy group.

When the copolymer is used in the coated layer, it is preferred to use copolymers obtained by copolymerizing the hydrophiclic monomer (AA) and the hydrophilic monomer (BB) in a copolymerization ratio of from about 1 to about 50 mol%, preferably 1 to 35 mol%.

When the polymer blend is used in the coated layer, it is preferred to use polymer blends obtained by blending about 0.1 to about 50 mol% of the hydrophilic polymer (AAA) with the hydrophilic polymer (BBB).

There is no particular limitation to a layer thickness of the coated layer used in the ion selective electrode of this invention; however, a thickness of the coated layer id generally in the range of from about 0.1 to about 30 iim, preferably 0.5 to 20 lim, more preferably 0.5 to 15 Clam.

Using polymer latexes, copolymers or polymer blends described above, halogen ion-permeable coated layers are formed in an appropriate method in response to shape of an electrode. In case that the electrode is formed in a linear shape, the coated layer can be provided by. immersing it in a polymer latex, a copolymer or a polymer blend (if necesary and desired, using an appropriate solvent), spraying a polymer latex, a copolymer or a polymer blend (if necessary and desired, using an appropriate solvent) on the electrode, etc. In the case that the electrode is in a sheet-like or film-like shape, the coated layer can also be formed as a coating, utilizing thin layer coating technique. In any methods, the use of a polymer latex which is an aqueous dispersion enables to operation for forming a coating layer in a safe and simple manner with low cost.In this regard, polymer latexes are preferred as materials for forming a coated layer for the electrode in accordance with the present invention.

Electrodes can be prepared in a conventional manner (see, RESEARCH DISCLOSURE, vol.

161, No. 16113, September in 1977). For example, electrodes can be prepared by directly connecting a lead with silver halide molded under pressure; in the case of a linear shape, by subjecting a part of a silver wire to electrolysis with halogen, or the like. Further, in case of using the silver halide electrode in a sheet-like or film-like shape, the electrode can be prepared by immersing a thin layer of silver in a silver halide solution, or by vacuum-depositing silver on an insulating film and then subjecting a part of the surface of the silver layer in the direction of thickness and surface to a chemical treatment (e.g., immersion in a solution containing an oxidizing agent and halogen ions for an appropriate period of time) to thereby convert silver in part into silver halide, etc.Also in the case of converting the entire surface of the silver layer into a silver halide layer, the electrode of the present invention can be constituted, but, in this case, once a silver halide layer is formed in the foregoing method, a chemical treatment using hypo, etc. is subjected to a part of silver halide to re-convert into silver.

A ratio of a silver layer to silver halide may be any ratio as far as a stable potential is ensured in measurement, but it is preferable in the range of from 5 to 50%. Methods for preparing silver/silver halide electrodes are described in detail in RESEARCH DISCLOSURE supra, U.S.

Patents 3,591,482, 3,502,560 and 3,806,439.

The coated layer for the electrode of the present invention is also applicable to the system as disclosed in Japanese Patent Application (OPI) 89741 /80 in which a silicone base plate is employed instead of a silver layer. In this system, a silver halide layer is provided generally on a semi-conductive material such as silicone dioxide/silicone by a vacuum deposition method, etc.

The electrodes of this type is effective for applying to electric field effect transistor.

The coated layer can also contain a small quantity of a surface active agent. Surface active agents can be suitably chosen from known agents in coating technique, but particularly preferred is fluorine type and silicon type surface active agents (e.g., Florad, FC-128, FC-170, etc. manufactured by 3M Co., Ltd.).

In the coated layer that is formed using polymer latexes of quaternary ammonium salts as polymer latexes, ion exchange in response to concentration occurs between the polymer latex and halogen ions to be measured; in such a case, the purpose of the present invention can be attained even if the coated layer possess no ion selectivity.

In the thus constructed electrode of the present invention, halogen ions, e.g., chlorine ions, along that are analytes-are selectively brought into contact with the silver halide electrode due to selective permeability of the coated layer so that a potential is interfered only with difficulty, by other halogen ions or interfering substances such as cyan ions, uric acid, etc.

In the case that the electrode of the present invention is employed as a single electrode, it is possible to measure halogen ions in combination with a standard electrode commercially available (direct method); it is also possible to measure concentrations halogen ions by bringing solutions containing halogen ions having concentrations of two kinds (one becomes a standard solution and another is a sample liquid) into contact with the electrode of the present invention, respectively, and migrating both solutions into a bridge by a capillary phenomenon to contact each other nearly at the center of the bridge, whereby an electromotive force in proportion to ion activity in the solutions generates and can be measured as a potential difference (with respect to details of a differential method, see Japanese Patent Application 89471/80.In this case, the silver halide layer (or silver layer) is electrochemially brought into contact with a means for measuring a potential difference so that the halogen ion concentration can easily be determined.

Examples for the material for a bridge include porous paper such as filter paper and blotting paper; membrane filter; and cotton products such as cotton fabrics.

Examples for cells for measurement and bridges are shown in U.S. Patent 4,053,381, 4,184,936, 4,171,246, 4,214,968 and 4,250,010, and they can be advantageously applied to the electrode of the present invention.

The electrode of this present invention can also include an electrode system prepared by vacuum depositing a silver halide layer on a semiconductor support, such as silicon dioxide/silicon and providing the coated layer on the silver halide layer. Details of such an electrode system using silicon dioxide/silicon semiconductor support are disclosed in U.S. Patent 4,199,412.

The electrode of the present invention has a high response rate and thereby is capable of responding in a very short time. Further, the potential drift is very small, and it can be used repeatedly and has very good stability over a period of time. The electrode of the present invention can be used for analysis requiring high accuracy, because the ion concentration can be quantitatively measured accurately and reproductively. The electrode of the present invention is produced by a simple production step and is ecconomically advantageous.

Hereafter, the present invention will be described in greater detail with reference to the examples below.

Example 1 1 g of silver having a purity of 99.9% was put in a tungsten basket. After a polyethylene terephthalate (hereafter often referred to as "PET") film (15 x 12 cm) having a thickness of 100 pm was disposed in a vacuum evaporation apparatus at a distance of about 30 cm from the evaporation source, the apparatus was operated to carry out vacuum evaporation under a degree of vacuum of 5 X 10-5 Torr till a thickness of a silver layer became about 900 nm. Then a vinyl polymer tape (width 1 cm) was allowed to adhere to both edges of the film (edges of 1 2 cm width). The remaining unprotected surface was immersed in a treating solution consisting of 7.12 g of potassium bichromate, 5 g of conc. hydrochloric acid and 1000 ml of distilled water for 45 seconds at 25"C, followed by washing with water and drying.

A latex composed of styrene-butyl acrylate-acrylic acid-hydroxymethylacrylamide (50:42:2:6 wt%) (hereafter referred to as Latex7) was coated on the silver halide layer described above.

The coated layer was dried at 60 to 100"C to form a coated layer having a dry thickness of 3 g/m2. A sample liquid was applied to the coated layer by dropping the liquid thereon to obtain an electrode.

The thus obtained electrode was connected by a bridge composed of agar salt with a commercially available standard electrode (HS-305DS, manufactured by Toa Denpa Kogyo Co., Ltd.), which was then connected with a potentiometer (digital voltmeter, Model 3456 A, manufactured by Hewlett Packard Co., Ltd.) (direct method).

As sample liquids, 10 to 50,ul of aqueous solutions of NaCI having 80, 100 and 1 20 mmol, which was adjusted to have NaNO3 ion activity of 1 60 mmol, were employed, respectively.

Results obtained are shown in Fig. 1.

As is seen from Fig. 1, a stable potential was obtained in a few minutes when using the electrode obtained in this example.

Example 2 Effect of Adding Polyethylene Glycol: Based on the solid content of the latex shown in Example 1, 0, 5 and 10 wt% of polyethylene glycol (PEG-400, polymerization degree of about 400, produced by Wako Junyaku Co., Ltd.) was added to Latex. A coated layer was formed in a manner similar to Example 1 except that the resulting coating composition was employed instead of Latex. A dry thickness of the thus formed coated layer was 3 g/m2.

According to the measurement method (direct method) shown in Example 1, efficiency of the coated layer was evaluated. Time required until a potential became stable when blood serum (commercially available "VERSATOL" having chlorine ion content of 102 mmol/l) was employed were as shown in Table 1.

Table 1 Coated Layer a b c PEG 400 (wt%) 0 5 10 Time (min.) 4 2.5 1.5 As is understood from Table 1, the potential became stable for a shorter period of time and the effect of polyethylene glycol to stabilization of the potential was greater, as the addition amount of polyethylene glycol was increased.

Example 3 Efficiency of the electrode (containing 10 wt% of PEG-400) prepared in the method shown in Example 2 was examined using commercially available standard serum by the direct method. A linear relationship having a potential slope of - 57 mV was observed between potential and logarithm of concentration.

The Cl- contents of standard serum used were 77, 91, 102, 107, 110 and 120 mmol/l, respectively.

Example 4 In accordance with a differential method using a pair of the electrode films prepared in Example 3, the relationship between Cl- content of commercially available standard serum and potential characteristic was examined.

After-applying a standard solution (trade name "VERSATOL", manufactured by General Diagnostic Co., Ltd.; hereafter the same) on one of the electrode films and applying a sample liquid having a different content of chlorine ions on the other electrode film, a potential generated 3 minutes after was measured using ORION-Microprocessor lonalyzer, Model 901 (manufactured by ORION Co., Ltd.).

Results obtained are shown in Fig. 2.

As is understood from Fig. 2, a good linear relationship suited for analysis was noted between the CI- ion content and potential.

Example 5 The electrode films obtained in Example 4 were stored at room temperature. Similar test was performed six months after. Quite the same linear relation as in Example 4 was obtained.

From these results, it is understood that the electrode of the present invention is extremely excellent also in stability with the passage of time.

Example 6 A latex composed of butyl methacrylate and a compound of formula:

(90: 10 in a weight ratio) (hereafter referred to as Latex 2) was coated onto an Ag/AgCI layer prepared in accordane with the procedure of Example 1 to form a coated layer having a dry thickness of 2 g/m2.

Using the thus obtained electrode, Cl- in standard serum was measured by both the direct method shown in Example 3 and the differential method shown in Example 4. Extemely good results were similarly obtained (see, Fig. 3).

Example 7 Likewise, good content-potential relation (potential slope, - 52 mV) was given also when electrodes containing a plurality of layers formed from latex composed of butyl methacrylateglycine methacrylate (80:20 in a weight ratio) (Latex-3).

Example 8 An electrode was prepared in a manner similar to Example 1 except that a coated layer having a dry thickness of 2 g/m2 was formed by coating a composition below: Composition of Coating: Latex-1 (15% aq. solution) 16 g Latex-4* (15% aq. solution) 10.5 g Water 72.5 g 2% Aq. Solution of Surfactant 1 g methyl methacrylate-acrylic acid-N-hydroxymethyl acrylamide = 94:2:4 Using the thus obtained electrode, Cl- was measured as in Example 1 and a good linear relationship was similarly noted between the Cl- content and potential. Its potential slope was - 54 mV.

Examples 9 to 14 Electrodes were prepared in a manner similar to Example 1 except that, after adding 2 g of 2% (ethanol-water= 9:1) of fluorine type surfactant (FC 128, manufactured by 3M) and 3 g of water to 10 g of a 10% aqeuous solution of Latex-1 used in Example 1 and further adding an aqueous solution of each of hydrophilic polymers described below thereto, the resulting mixture was coated onto the AgCI layer to form a coated layer, respectively. In any case, the coated layer having excellent surface property was obtained.

Using each of the thus obtained electrodes, Cl- was measured. In any case, excellent potential characteristics were obtained.

Example No. Hydrophilic Polymer Amount Added(g) 9 PEG 60,000 (10% aq. solution) (polymerization degree, ca. 60,000) 6 10 Polyacrylamide (10% aq.

solution) 1 11 Polyvinyl pyrrolidone (5% aq. solution) 2 1 2 Carboxymethyl cellulose (10% aq. solution) 2 13 Methyl cellulose (1% aq.

solution) 1 1 4 Hydroxyethyl cellulose (1% nq. solution) 1 Example 15 Electrodes were prepared in a manner similar to Example 1 except that a subbing layer was provided on the AgCI layer by coating each of the hydrophilic polymers shown in Examples 9 to 14 on the AgCI layer and further thereon was provided a coated layer by coating each of latexes employed in Examples 1 to 8, respectively, followed by drying.

In the evaluation test, each of the electrodes gave good results.

Example 16 Effect of Br-: Abnormal serum was prepared by diluting commercially avaiable serum ("VERSATOL", (R.T.M.) manufactured by General Diagnostic Co., Ltd.) with 0.5 mmol of an aqueous KBr solution.

As a standard solution, the solution obtained by diluting VERSATOL with distilled water was employed.

Using Electrode b obtained in Example 2 and the electrode obtained in Example 6, potential generating 3 minutes after contact of the standard solution with the sample solution was measured in accordance with the direct method and the differential method.

Results are shown in Table 2 below.

For purpose of comparison, the measurement was also performed with the electrodes containing no coated layer.

Table 2 No Coated Layer Latex Latex-2 Direct Method -6.lmV - 0.3 mV -0.4mV Differential Method - 7.7 mV - 0.2 mV - 0.3 mV The potential of the standard solution should be O mV and the closer to zero the found potential is, the more accurately should the Cl- content be measured.

As is clear from the table above, the potentials were not in response to the Cl - content due to interference of Br- and interference by Br- was clearly noted, when no coated layer was provided. On the other hand, when using the electrodes of the present invention which contained the coated layers, interference by Br- was substantially completely eliminated.

Example 17 Using the electrode b prepared in Example 2, Cl- in a sample liquid obtaned by adding, as interfering substances, ascorbic acid, glucose, glutathion, mercaptopurine, BUN (urea and nitrogen) and billirubin to standard serum was measured in a manner similar to Example 1 6 in accordance with the direct method and the differential method described above. These interfering substances were substantially removed by the coated layer, and a bias of the potential obtained were almost nearly zero.

Example 18 An electrode was prepared in a manner similar to Example 1 except that a coated layer (dry thickness, 2 g/m2) was formed by coating a composition below onto the Ag/AgCI layer.

Coating Composition Latex5* (15% aq. solution) 10 g 5% Aq. Gelatin Solution 5 g Water 10 g * Styrene-N,N,N-trihexyl-N-vinylbenzyl ammonium chloride (5:95) Using the thus obtained electrode, Cl - was measured and, a good linear relationship was noted between the content and potential. Its potential slope was - 45 mV.

Example 19 An electrode was prepared in a manner similar to Example 1 except that a coated layer was formed by coating a composition below on the Ag/AgCI layer.

Coating Composition: Latex-6* (13% aq. solution) 10 g 5% Aq. Gelatin Solution 3 g Water 10 9 Latex6:

Using the thus obtained electrode, Cl- was measured as in Example 1, and a good linear relationship was noted between the content and potential.

Example 20 Onto a PET film having a thickness of 100 jim, metallic silver was deposited in a thickness of about 9000 angstrom in vacuum. Then, a vinyl polymer tape (width 1 cm) was allowed to adhere to one edge of the aforesaid deposited film to thereby protect a part of the silver surface and the remaining surface was impregnated with a treating solution composed of potassium bichromate-conc. hydrochloric acid-water (7 g-5 g-1000 9) at 25"C for 45 seconds, followed by washing with water and drying. Thus, an AgCI layer was provided on the silver layer.

In a mixture of 35 g of propyl alcohol and 1 5 g of water, 5 g of a copolymer of ethylene-vinyl alcohol (3:7) was dissolved and small quantities of PEG 400 and Triton (R.T.M) X-100 (manufactured by Rohm 8 Haas Co., Ltd.) were added to the resulting solution. Thereafter, the mixture was coated on the aforesaid AgCI surface in a dry thickness of 2 g/m2 followed by coating and drying. After stripping the vinyl polymer tape off, an electrode was obtained.

Example 21 In a manner similar to Example 1, an electrode was obtained except that 5 9 of a copolymer of vinyl acetate-vinyl pyrrolidone (9:1) was dissolved in 45 g of ethanl and 0.2 g of PEG 400 and 3 drops of Triton X-100 (manufactured by Rohm 8 Haas Co., Ltd.) were added to the resulting solution and the resulting mixture was coated onto the AgCI layer followed by drying.

Potential-Time Response (1) Direct Method A sample liquid was applied to each of the coated layers of the electrodes obtained in Examples 1 and 2 described above. A commercially available standard electrode (manufactured by Toa Denpa Kogyo Co., Ltd., Model HS-305DS) was connected with each of the electrode by a bridge composed of agar salt, which was then connected with a potentiometer (digital voltmeter, 3456A, manufactured by Hewlett Packard Co., Ltd.) to directly measure a potential (direct method).

As sample liquids, NaCI aqueous solutions having concentrations of 80, 100 and 1 20 mmol/l were employed (wherein the intensity of the salt was adjusted to 1 60 mmol/l as NaNO3).

Results obtained are shown in Figs. 4 (with the electrode obtained in Example 20) and Fig. 2 (with the electrode obtained with Example 21).

(2) Differential Method A potential-time response was evaluated by the differential method in which the electrode of Example 1 was used, and commercially available sera having different chlorine ion contents were used as sample liquids and commercially available serum having a normal value in chlorine content (100 mmol/l) as a standard liquid. Potentials read with a potentiometer three minutes after the application of the liquids were plotted, which is shown in Fig. 6.

Example 22 In a manner similar to Example 1, an electrode was prepared except that 5 9 of a vinyl acetate-vinyl imidazole (81:20) copolymer was dissolved in a solvent mixture of 75 9 of ethanol and 20 9 of ethyl acetate and the solution was coated on the AgCI layer in a dry thickness of 2.5 g/m2 to provide a protective layer.

Also in the case of using the thus obtained electrode, a good potential-time response was similarly obtained.

Example 23 An electrode was obtained in a manner similar to Example 1 except that a copolymer described below was employed as a copolymer for the protective layer.

Differential Method for Measurement of Br-: Using the thus obtained electrode, potentials were determined with liquid samples obtained by diluting a commercially available serum "VERSATOL" (manufactured by General Diagnostic Co., Ltd.) with water and a 0.5 mmol KBr aqueous solution, respectively, by the differential method.

Readings on a potentiometer are shown in Table 3 below, in which results obtained with the electrodes of Examples 1 and 2 and an electrode for control containing no protective layer by the same measurement method are also shown.

Table 3 Electrode Potential (mV) Example4 -1.7 Example 1 - 2.0 Example 2 - 1.2 Comparison Example (no protective layer) - 7.7 An electrode which undergoes interference with interfering substances shows a potential as close as 0 mV. As is evident from the results described above, the electrodes of the present invention are all sufficiently prevented from inferference.

Example 24 In a solvent mixture of 55 9 of ethanol and 20 9 of ethyl acetate, 4.6 g of polyvinyl acetate and 0.4 g of polyvinyl pyrrolidone were dissolved and 0.25 9 of polyethylene glycol (PEG-400, polymerization degree, about 400) and 5 drops of a surface active agent (a 1 % methanol solution of Triton X-100, manufactured by Rohm 8 Haas Co., Ltd.) were added to the resulting solution. The obtained solution was coated on a silver/silver chloride electrode in a layer thickness of 2.7 jim to prepare Sample No. 1.

The silver/silver chloride electrode was prepared by forming a silver layer on a polyethylene terephthalate by vacuum deposition, protecting a part of the silver layer with a vinyl polymer tape, impregnating the surface of the remaining silver layer with a solution of potassium bichromate and hydrochloric acid at about 25"C for 45 seconds and then stripping the vinyl polymer tape off.

Example 25 In 50 9 of methyl ethyl ketone and 1 5 9 of ethanol, 5 9 of polymethyl methacrylate and 0.4 g of polyvinyl pyrrolidone were dissolved and, 0.25 g of polyethylene glycol (PEG-400) and 5 drops of a surface active agent (a 1 % methanol solution of Triton X-100) were further added to the solution. The thus obtained solution was coated on the silver/silver chloride electrode described in Example 24 in a layer thickness of 2.5 jim after drying and then treated as in Example 24 to prepare Sample No. 2.

Example 26 In 80 g of methanol, 5 9 of nylon (CM-8000, manufactured by Toray Co., Ltd.) and 0.4 9 of polyvinyl pyrrolidone were dissolved and, 0.25 9 of polyethylene glycol (PEG-400) and 5 drops of a surface active agent (a 1 % methanol solution of Triton X-1 00) were further added to the solution. The thus obtained solution was coated on the silver/silver chloride electrode described in Example 24 in a layer thickness of 3.0 ym after drying and then treated as in Example 24 to prepare Sample No. 3.

Example 27 In 50 9 of methyl ethyl ketone and 1 5 9 of ethanol, 5 g of polymethyl methacrylate and 1 9 of polyvinylimidazole were dissolved and, 0.25 g of polyethylene glycol (PEG-400) and 5 drops of a surface active agent (a 1 % methanol solution of Triton X-1 00) were further added to the solution. The thus obtained solution was coated on the silver/silver chloride electrode described in Example 24 in a layer thickness of 3.3 jim after drying and then treated as in Example 24 to prepare Sample No. 4.

Example 28 In 80 g of methanol, 5 g of nylon and 1 g of polyvinylimidazole were dissolved and, 0.25 g of polyethylene glycol (PEG-400) and 5 drops of a surface active agent (a 1 % methanol solution of Triton X-100) were further added to the solution. The thus obtained solution was coated on the silver/silver chloride electrode described in Example 24 in a layer thickness of 3.4 jim after drying and then treated as in Example 24 to prepare Sample No. 5.

Example 29 In 85 g of methanol and 20 9 of ethyl acetate, 5 g of polyvinyl butyral and 1.5 g of polyvinyl pyrrolidone were dissolved and, 0.25 9 of polyethylene glycol (PEG-400) and 5 drops of a surface active agent (a 1 % methanol solution of Triton X-1 00) were further added to the solution. The thus obtained solution was coated on the silver/siiver chloride electrode described in Example 24 in a layer thickness of 3.0 jim after drying and then treated as in Example 24 to prepare Sample No. 6.

Example 30 In 75 9 of ethanol and 20 9 of ethyl acetate, 5 g of polyvinyl butyral and 1 9 of polyvinylimidazole were dissolved and, 0.25 g of polyethylene glycol (PEG-400) and 5 drops of a surface active agent (a 1 % methanol solution of Triton X-1 00) were further added to the solution. The thus obtained solution was coated on the silver/silver chloride electrode described in Example 24 in a layer thickness of 3.4 jim after drying and then treated as in Example 24 to prepare Sample No. 7.

Example 31 In 50 9 of methyl ethyl ketone and 1 5 g of ethanol, 5 9 of polybutyl methacrylate and 1 g of polyvinylimidazole were dissolved and, 0.25 g of polyethylene glycol (PEG-400) and 5 drops of a surface active agent (a 1 % methanol solution of Triton X-100) were further added to the solution. The thus obtained solution was coated on the silver/silver chloride electrode described in Example 24 in a layer thickness of 2.7 jim after drying and then treated as in Example 24 to prepare Sample No. 8.

Example 32 In 50 g of methyl ethyl ketone and 1 5 g of ethanol, 5 9 of polybutyl methacrylate and 0.6 g of polyvinylpyrrolidone were dissolved and, 0.25 9 of polyethylene glycol (PEG-400) and 5 drops of a surface active agent (a 1 % methanol solution of Triton X-100) were further added to the solution. The thus obtained solution was coated on the silver/silver chloride electrode described in Example 24 in a layer thickness of 2.8 pm after drying and then treated as in Example 24 to prepare Sample No. 9.

Example 33 In a solvent mixture of 75 g of ethanol and 20 9 of ethyl acetate, 5.0 9 of a copolymer of vinyl acetate/vinylpyrolidone (95/5) and 0.5 g of polyvinylpyrrolidone were dissolved and, 0.25 9 of polyethylene glycol (PEG-400) and 5 drops of a surface active agent (a 1% methanol solution of Triton X-1 00) were further added to the solution. The thus obtained solution was coated on the silver/silver chloride electrode described in Example 24 in a layer thickness of 4.2 ym after drying and then treated as in Example 24 to prepare Sample No. 10.

Measurement of Potential (1) With the samples prepared in accordance with Examples 24 through 33, potentials were measured 10 minutes after the application of liquids by the direct method, by applying 25 yl of an aqeuous 100 mN sodium chloride solution onto each of the thus prepared electrodes and connecting by an agar bridge with a reference electrode. As the reference electrode, a silver/silver chloride electrode (Model HS 305DS, manufactured by Toa Denpa Co., Ltd.) was employed.

Potentials of the electrodes 10 minutes after the application are shown in Table 4.

Fig. 7 shows relatoinship between the potentials and time response of the electrode obtained in Example 25.

Table 4 Sample No. Potential (mV) 1 96.8 2 98.6 3 100.4 4 98.8 5 99.4 6 96.1 7 96.2 8 95.9 9 97.0 10 97.4 (2) Using the electrodes (Sample Nos. 11 to 15) obtained in Examples 24 to 28, potentials were measured by the direct method described above. Changes in potentials from 5 minutes to 10 minutes in this case are shown in Table 5. It is understood that the electrodes in accordance with the present invention show extremely stable potentials.

Table 5 Sample No. Change in Potential (mV) 11 -0.29 12 -0.12 13 -0.57 14 -0.12 15 -0.33 Example 34 An electrode containing a coated layer composed of polymethyl methacrylate and polyvinylpyrrolidone was prepared as in Example 25.

Commercially available serum ("VERSATOU', trade name, manufactured by General Diagnostic Co., Ltd.) was diluted with distilled water and with an aqueous 0.5 mM KBr solution. By the aforesaid method (direct method), a potential between both dilutions was measured three minutes after and was - 0.25 mV.

When compared with a control sample containing no protective layer which showed - 6.1 mV, the electrode of the present invention gave extremely good results for bromine ions.

Examples 35 to 37 Using the electrodes (Sample Nos. 16, 1 7 and 18) obtained in Examples 25, 27 and 28, influence of bromin ions potential was examined in accordance with the measurement method (differential method) disclosed in Japanese Patent Application (OPI) 89741/80 (corresponding to U.S. Patents 4,199,419 and 4,199,412).

As a reference liquid, commercially available serum (tradename "VERSATOL", manufactured by General Diagnostic Co., Ltd.) was employed and as a sample liquid, a mixture of said serum and 0.5 m/l of KBr was employed. Potentials were read out three minutes after the application of the liquids and are shown in Table 6.

Table 6 Composition of Change in Sample No. Coated Layer Potential (mV) 16 Polymethyl methacrylate- - 0.9 Polyvinylpyrrolidone 17 Polyamide-Polyvinyl- - 0.35 imidazole 18 Polyamide-Polyvinyl- - 1.33 imidazole Comparison No Coated Layer - 7.7 While the invention has been described in detail and with reference to specific embodiment thereof, it will be apparent to one skilled ir the art that various changes and modifications can be made therein without departing from tha spirit and scope thereof.

Claims (17)

1. In an electrode for measuring halogen ions which comprises a silver layer having provided thereon, in sequence, a silver halide layer and a coated layer capable of allowing permeation of halogen ions, the improvement in which said coated layer capable of allowing permeation of halogen ions is composed of one member selected from a polymer latex, a copolymer and a polymer blend.

2. The electrode of claim 1 wherein said polymer latex is a polymer latex obtained by emulsion polymerization of (I) each of at least one monomer selected from the group consisting of monomers of Group (A) and at least one monomer selected from the group consisting of monomers of Group (B) represented by formula (IB); or (II) each of at least one monomer selected from the group consisting of monomers of Group (A), at least one monomer selected from the group consisting of monomers of Group (B) represented by formula (IB) and at least one monomer selected from the group consisting of monomers of Group (C).

Group (A): Ethylene-type monomers having at least one free carboxylic acid group, free sulfonic acid group or a free phosphoric acid group or a salt thereof: Group (B): Monomers represented by formula (IB):

wherein X, V: hydrogen atom, methyl group, halogen atom, or -COOR' group Y: hydrogen atom, methyl group, halogen atom or -(CH2)nCOOR2 Z: aryl group, -COOR3 or -OCOR5 R', R2, R3: they may be the same or different and represent an aliphatic group or an aryl group.

n: O, 1, 2 or 3 Group (C): Unsaturated monomers other than monomers belonging to Group (A) and Group (B) and copolymerizable with monomers of Group (A) or Group (B), selected from the group consisting of an acrylamide, a methacrylamide, an allyl compound, a vinyl ether, a vinyl ketone, an olefin, a vinyl heterocyclic compound, an unsaturated nitrile and a polyfunctional monomer.

3. The electrode of claim 2 wherein said monomers of Group (A) are ethylene type monomers selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, a monoalkyl itaconate, a monoalkyE maleate, citraconic acid, styrenesulfonic acid, vinylbenzylsulfonic acid, vinylsulfonic acid, an acryloyloxyalkylsulfonic acid, a methacryloyloxyalkylsulfonic acid, an acrylamidoalkylsulfonic acid, a methacrylamidoalkylsulfonic acid, an acryloyloxyalkyl phosphonate and a methacryloyloxyalkyl phosphonate.

4. The electrode of claim 2 wherein said polymer latex is a polymer latex produced by emulsion polymerization of each of at least one monomer selected from the group consisting of monomers of Group (D) at least one monomer selected from the group consisting of monomers of Group (E) and at least one monomer selected from the group consisting of monomers of Group (F): Group (D):Monomers represented by formula (llD):

wherein R4 represents a hydrogen artom or a methyl group; T represents a hydrogen atom or an aliphatic group; Q represents a -CH2-OCOR group, a

group, a -CH2OR2d group, a

group or a

group; R" represents an aliphatic group or an aryl group; Ria and R'b, which may be the same or different, each represents an aliphatic group or R'" and Rib may combine to form a ring; R2d represents a hydrogen atom or an aliphatic group;R3d, R4d, R5d, R6d and R7d, which may be the same of different, each represents a hydrogen atom or a -CH2OR2d group provided that all of the R3d to R7d do not represent hydrogen atoms at the same time; and W represents an atomic group necessary to form a ring together with the -N-CO- linkage.

Group (E): Polymerizable ethylenically unsaturated monomers having at least a free carboxylic acid group, sulfonic acid group or phosphoric acid group or a salt thereof: Group (F): Ethylene type monomers other than those monomers of Group (A) and Group (B) which are copolymerizable with the monomers of Group (D) and Group (E).

5. The electrode of claim 2 wherein said polymer latex is a blend of a polymer latex (I) obtained by emulsion polymerization of each of at least one monomer selected from the group consisting of monomers of Group (A) and at least one monomer selected from the group consisting of monomers of Group (B) represented by formula (IB); or each of at least one monomer selected from the group consisting of monomers of Group (A), at least one monomer selected from the group consisting of monomers of Group (B) represented by formula (IB) and at least one monomer selected from the group consisting of monomers of Group (C); and a polymer latex produced by emulsion polymerization of each of at least one monomer selected from the group consisting of monomers of Group (D), at least one monomer selected from the group consisting of monomers of Group (E) and at least on monomer selected from the group consisting of monomers of Group (F): Group (A): Ethylene-type monomers having at least one free carboxylic acid group, free sulfonic acid group or a free phosphoric acid group or a salt thereof: Group (B): Monomers represented by formula (IB):

wherein X, V: hydrogen atom, methyl group, halogen atom, or -COOR' group Y: hydrogen atom, methyl group, halogen atom or -(CH2)nCOOR2 Z: aryl group, -COOR3 or -OCOR5 R', R2, R3: they may be the same or different and represent an aliphatic group or an aryl group.

n: 0, 1, 2 or 3 Group (C): Unsaturated monomers other than monomers belonging to Group (A) and Group (B) and copolymerizable with monomers of Group (A) or Group (B), selected from the group consisting of an acrylamide, a methacrylamide, an allyl compound, a vinyl ether, a vinyl ketone, an olefin, a vinyl heterocyclic compound, an unsaturated nitrile and a polyfunctional monomer.

Group (D): Monomers represented by formula (IID):

wherein R4 represents a hydrogen atom or a methyl group; T represents a hydrogen atom or an aliphatic group; Q represents a -CH2-OCOR group, a

group, a -CH2OR2d group, a

group or a

group; R" represents an aliphatic group or an aryl group; Ria and R'b, which may be the same or different, each represents an aliphatic group or R'" and Rib may combine to form a ring; R2d represents a hydrogen atom or an aliphatic group;R3d, R4d R5d, R6d and R7d, which may be the same of different, each represents a hydrogen atom or a -CH2OR2d group provided that all of the R3d to R7da do not represent hydrogen atoms at the same time; and W represents an atomic group necessary to form a ring together with the -N-CO- linkage.

Group (E): Polymerizable ethylenically unsaturated monomers having at least a free carboxylic acid group, sulfonic acid group or phosphoric acid group or a salt thereof.

Group (F): Ethylene type monomers other than those monomers of Group (A) and Group (B) which are coplymerizable with the monomers of Group (D) and Group (E).

6. The electrode of claim 1 wherein said coated layer capable of allowing permeation of halogen ions is composed of a mixture obtained by incorporating a hydrophilic polymer into said polymer latex or said blend thereof.

7. The electrode of claim 6 wherein said hydrophilic polymer is incorporated in an amount of not greater than 50 wt% based on the total weight of said mixture.

8. The electrode of claim 7 wherein said hydrophilic polymer is at least one selected from hydrophilic polymers obtained by polymerizing at least one of monomers represented by formula:

wherein P represents a hydrogen atom or an alkyl group; Q represents a

nucleus (wherein Z represents an atomic group necessary for completing a pyrrolidone nucleus, an imidazole nucleus, an oxazolone nucleus or a succinimido nucleus), a 2-pyridyl group, a 4pyridyl group, a hydroxycarbonyl group, an aminocarbonyl group, an alkylaminocarbonyl group, a substituted alkylaminocarbonyl group, a dialkylaminocarbonyl group, a substituted dialkylaminocarbonyl group, a sulfonyl group, a hydroxy group, an amino group, a substituted amino group, a carboxyaryl group, a sulfoaryl group, a hydroxyethoxycarbonyl group, a sulfonic acid group, a phosphoric acid group, a substituted alkoxy group.

9. The electrode of any one of claims 1 to 8 wherein said halogen ions are chlorine ions and said silver halide is silver chloride.

10. The electrode of any one of claims 1 to 9 wherein said coated layer capable of allowing permeation of halogen ions further contains a surface active agent.

11. The electrode of any of claims 1 to 10 wherein a doped silicon support is additionally comprised and a silicon dioxide layer comprising is further laminated on the doped silicon support, as a means for effecting differential measurement.

1 2. The electrode of any one of claims 1 to 11 wherein said silver halide layer is laminated on said silver layer and electrochemically connected with said silver layer.

1 3. The electrode of claim 1 wherein said copolymer is a copolymer obtained by copolymerizing at least one of hydrophobic monomers (AA) represented by formula (V) below and at least one of hydrophilic monomers (BB) represented by formula (VI) below: Hydrophobic Monomer (AA):

Hydrophilic Monomer (BB):

In formula (V), R'O represents a hydrogen atom, an alkyl group, or a halogen atom;R20 represents an alkyl group, a substituted alkyl group, an alkoxycarbonyl group, a substituted alkoxycarbonyl group, an alkoxycarbonylalkyl group, an alkylcarboxy group, a substituted alkylcarboxy group, an alkylcarboxyalkyl group, a substituted alkylcarboxyalkyl group, an aryl group, a substituted aryl group, a monoalkylaminocarbonyl group, a substituted monoalkylaminocarbonyl group, a dialkylaminocarbonyl group, a substituted dialkylaminocarbonyl group or a halogen atom.

In formula (VI), R30 represents a hydrogen atom or an alkyl group; R40 represents a

nucleus (wherein z represents an atomic group necessary for completing a pyrrolidone nucleus, an imidazole nucleus, an oxazolone nucleus or a succinimido nucleus), a 2-pyridyl group, a 4-pyridyl group, a hydroxycarbonyl group, an aminocarbonyl group, an alkylaminocarbonyl group, a substituted alkylaminocarbonyl group, a dialkylaminocarbonyl group, a substituted dialkylaminocarbonyl group, a sulfonyl group, a hydroxy group, an amino group, a substituted amino group, a carboxyaryl group, a sulfoaryl group, a hydroxyethoxycarbonyl group, a sulfonic acid group, a phosphoric acid group, a substituted alkoxy group.

1 4. The electrode of claim 1 3 wherein said copolymer is a blend of at least two of said copolymers.

1 5. The electrode of claim 1 3 or 14 wherein at least one of a hydrophilic polymer obtained by polymerizing at least one of monomers represented by formula below is added to said copolymer:

wherein P represents a hydrogen atom or an alkyl group;Q represents a

nucleus (wherein Z represents an atomic group necessary for completing a pyrrolidone nucleus, an imidazole nucleus, an oxazolone nucleus or a succinimido nucleus), a 2-pyridyl group, a 4 pyridyl group, a hydroxy-carbonyl group, an aminocarbonyl group, an alkylaminocarbonyl group, a substituted alkylaminocarbonyl group, a dialkylaminocarbonyl group, a substituted dialkylami nocarbonyl group, a sulfonyl group, a hydroxy group, an amino group, a substituted amino group, a carboxyaryl group, a sulfoaryl group, a hydroxyethoxycarbonyl group, a sulfonic acid ,group, a phosphoric acid group, a substituted alkoxy group.

16. The electrode of claim 1 wherein said polymer blend comprises at least oneof hydrophobic polymers selected from Group (AAA) described below and at least one of hydrophilic polymers selected from Group (BBB) described below.

(AAA) Hydrophobic Polymer (AAA-1): Hydrophobic polymers obtained by polymerizing at least one monomer represented by formula (V):

wherein R'O represents a hydrogen atom, an alkyl group, or a halogen atom; R20 represents an alkyl group, a substituted alkyl group, an alkoxycarbonyl group, a substituted alkoxycarbonyl group, an alkoxycarbonylalkyl group, an alkylcarboxy group, a substituted alkylcarboxy group, an alkylcarboxyalkyl group, a substituted alkylcarboxyalkyl group, an aryl group, a substituted aryl group, a monoalkylaminocarbonyl group, a substituted monoalkylaminocarbonyl group, a dialkylaminocarbonyl group, a substituted dialkylaminocarbonyl group or a halogen atom.

(AAA-2): Polyamides (AAA-3): Ethyl cellulose (BBB) Hydrophilic Polymer (BBB-1): Hydrophilic polymers obtained by polymerizing at least one monomer represented by formula (Vl):

wherein R30 represents a hydrogen atom or an alkyl group;R40 represents a

nucleus (wherein Z represents an atomic group necessary for completing a pyrrolidone nucleus, an imidazole nucleus, an oxazolone nucleus or a succinimido nucleus), a 2-pyridyl group, a 4pyridyl group, a hydroxycarbonyl group, an aminocarbonyl group, an alkylaminocarbonyl group, a substituted alkylaminocarbonyl group, a dialkylaminocarbonyl group, a substituted dialkylaminocarbonyl group, a sulfonyl group, a hydroxy group, an amino group, a substituted amino group, a carboxyaryl group, a sulfoaryl group, a hydroxyethoxycarbonyl group, a sulfonic acid group, a phosphoric acid group, a substituted alkoxy group.

(BBB-2): Polyethylene glycol (BBB-3): Methyl cellulose (BBB-4): Carboxymethyl cellulose (BBB-5): Hydroxyethyl cellulose (BBB-6): Maleic acid polymers (BBB-7): Maleic anhydride polymers (BBB-8): Fumaric acid polymers

1 7. An electrode as claimed in claim 1, substantially as hereinbefore described with reference to any of the Examples and/or the accompanying drawings.