CN1134191A

CN1134191A - Method and device for determination of substances in solution

Info

Publication number: CN1134191A
Application number: CN95190763A
Authority: CN
Inventors: G·哈姆比利则
Original assignee: Zuellig AG
Current assignee: Hach Lange SARL
Priority date: 1994-08-12
Filing date: 1995-08-11
Publication date: 1996-10-23
Also published as: JPH09504376A; WO1996005509A1; KR960705204A; EP0729576A1; CA2173464A1

Abstract

Described is a method for the determination of substances in solution, in particular oxygen, the method using an open, membrane-less system with a potentiostatic array of three electrodes and mechanical self-cleaning facilities. According to this method, the necessary reference potential is generated by a current-carrying metal electrode, thus making it possible to use a wide range of electrode materials and permitting cross-field effects to be eliminated in the determination of substances in solution. The device used calls for the potentiostat, control electronics and signal processing to be integrated in one and the same test probe. It can be used for the determination of various analytes. The method described is suitable for use in industrial processes, in particular waste-water and drinking-water processing systems, the food-processing industry, the pharmacological industry and the biotechnology field, as well as in chemical-technical processes.

Description

Measure the method and apparatus of dissolved substance

The relevant device of the method for operating and the claim 5 of probe and one three electrode lay-out is shown in the survey with mechanical self-purification that the present invention relates to an a kind of opening by claim 1.

The measurement of dissolved oxygen DO for example can be undertaken by DIN38408, both can use the oxygen probe (DIN38408-G22) of iodometry (pressing the DIN38408-G21Winkler method) or also available band barrier film to measure the oxygen that dissolves here.What belong to the oxygen probe of being with barrier film has, as Clark-sensor, Maekereth-sensor, and Connery, Taylor and Muly sensor.They be the structure and the electrode used therein type of material of sensor according to difference.

Measuring principle based on oxygen probe is same.And be expressed as follows: in the total concentration, a part that is equivalent to dissolved oxygen DO will play electrochemical reaction on an electrode therein.That here flow and have functional relation as the electric current of initial measurement signal record and the concentration of oxygen.Can be in order to produce the necessary electrode potential of reaction by polarization, perhaps by suitable electrode reaction in system self generation by means of external power source.

The described device of the latter can be learnt from EP144325.This part patent specification has been described a device that is made of two electrodes, and they come down to be made of different materials, and the end face that works except them of two electrodes was exposed to here, all the other were all sealed with insulating material.For the end face of clearing up these electrodes is prepared one in advance movably, drive lapping device, electrode and insulating material are when grinding, and distance should remain unchanged between its shape, size and the effective surface electrode.In order to produce measuring-signal, make full use of following effect, promptly between an amalgam electrode (negative electrode) and ferroelectric utmost point or zinc electrode (anode), produce an electric current, its size is relevant with the actual concentrations of oxygen.Polarization just produces by the current potential that forms on anode.This definition is the with good conditionsi of part, and is subjected to the influence of various factors, and for example oxygen signal is subjected to horizontal interference.Consequently oxygen signal unstable and by horizontal influence cause non-linear, such as have surfactant in measuring solution, they derive from washing agent and cleanser.Another shortcoming is to have only the small number of electrodes material available, and this has just limited the application of probe when measuring certain analyte.

Task of the present invention is to propose a kind of method that is used for measuring the solution electroactive material, oxygen particularly, Xiang Guan a kind of device therewith, it based on a kind of opening and not with the measuring sonde with mechanical self-purification of barrier film, by means of one three electrode lay-out, not being subjected in fact laterally influences, always the most suitable problems of measurement, and can improve the linearity by it, improve the stability at zero point simultaneously.

According to task of the present invention, will be resolved with claim 1 described method of full text and the described device of claim 5 full text.The present invention is further elaborated by drawing below.

Fig. 1. have three electrode lay-out principle schematic of current loading reference electrode.

Fig. 2. have the configuration example of an oxygen probe of three electrode lay-outs.

Fig. 3. have the structure top view of an oxygen probe of three electrode lay-outs.

Fig. 4. the oxygen signal with the oxygen signal of three electrode lay-outs and other devices up to the present compares.

Fig. 5. at a kind of oxygen signal that contains in the sulfide solution with three electrode lay-outs.

Fig. 6. at a kind of oxygen signal that contains in the surfactant solution with three electrode lay-outs.

Fig. 1 has showed the principle schematic of three electrode lay-outs.In the container 1 that fills the solution that contains dissolved substance 2, place a working electrode 4, a counter electrode 5 and a reference electrode 6.Preferably can be measured by amperometry, be the material of electrochemical activity under given polarizing voltage, as oxygen, chlorine and other sanitizer and heavy metal.Working electrode 4 for example is made of noble metal, noble metal-alloy, steel, graphite material, vitreous carbon or conducting polymer.Counter electrode 5 mainly is to be made of noble metal, steel, simple metal, graphite material or vitreous carbon.Reference electrode 6 is to be made of iron, zinc, silver, copper or alloy.Reference electrode 6 will be placed near working electrode 4, so that reach an as far as possible little ohmic voltage drop.In order to operate this measurement mechanism, settle the voltage stabilizer 7 of a repacking in advance, it connects counter electrode 5 and reference electrode 6 respectively by lead 8 and 9.Working electrode is to be connected by the particle of lead 10 with voltage stabilizer 7.Voltage stabilizer 7 consists essentially of an adjustable controller 11, its output terminal provide one relevant with the defined current potential of reference electrode, at output terminal 12 selectable voltages.The voltage stabilizer 7 of repacking contains a constant current source 13 in addition, and the connected mode of constant current source is that reference electrode is always charged with constant current density in branch circuit.The main circuit of measuring system is by voltage stabilizer 7 beginnings, through lead 8, counter electrode 5, the solution that contains dissolved substance 2, working electrode 4 and lead 10.Instrument 14 is the electric currents that are used for measuring in the lead 8.The solution that contains dissolved substance 2 is a kind of electrolyte, and its electric conductivity is relevant with the type of solution material, and can change in very wide scope.

By using three such electrode lay-outs, can demarcate and align polarizing voltage arbitrarily, thereby drop to minimum, and improve the linearity and balanced null point laterally influencing.Except described these advantages up to the present, laterally influence, improve beyond the linearity and the stability comprising reducing, also be surprised to find that the possibility that very big dirigibility and combination are arranged aspect electrode material.These advantages are not only to adopt described up to now amalgam electrode, and equally also are present in the nontoxic electrode of the common food of many kinds, for example by noble metal, steel, graphite material, vitreous carbon or conducting polymer, as the electrode of formations such as polypyrrole.Because the realization of autotelic selection electrode material possibility, another shortcoming up to the present also is overcome.Aspect counter electrode, other material of also successful usefulness replaces used iron/zinc at present, and its advantage is a chemically stable, as special steel, noble metal or vitreous carbon.

Based on the fact that does not have the probe that barrier film covers, never consider traditional reference electrode concerning an opening.Here select a brand-new route.Here, the current potential that (as: by iron) forms on a metal electrode exerts an influence to mixed potential.In order to utilize the reference electrode of a ferroelectric utmost point, its current potential and the oxygen content and the impurity of solution are had nothing to do as voltage stabilizing measurement oxygen.The realization of this point, people are by giving in advance an anode current, make it to flow through reference electrode, and the cathode portion electric current when being suppressed at mixed potential and forming.By a time-invariant current loading of setting size, can make the oxygen dependence of the reference electrode that this kind electric current passes through drop to a unexpected minimal value, maximum only ± 10mV.This shows that current potential shows wonderful very little sensitivity, particularly sulfide and iron to impurity.This good current potential is constant can to guarantee a duty with voltage stabilizing of three electrode lay-outs mechanical self-purification, opening.As electrode material, except iron also can be used other simple metal, as zinc, silver and copper and alloy.

Fig. 2 shows that a survey with three electrode lay-outs shows the embodiment of probe, and it has a handle 18 as insertion type probe.Whole three electrodes are positioned at same plane in a special cup 16.These essential electronic packages (voltage stabilizer and measurement numerical value arrangement parts) are the ingredients of probe, and are installed in the shell of CD-ROM drive motor 15.Its advantage is used for signal and transmits that to have only two

lead

17a and 17b be necessary, and the transmission of hundreds of rice lead-in wire all is feasible.

Fig. 3 shows a top view with measuring sonde embodiment of three electrode lay-outs.Working electrode 4, reference electrode 6 and counter electrode 5 are implemented by concentric, also can be undertaken by other geometric layout here.It is very little that the area of reference electrode 6 is compared with the area of working electrode 4, and their area is all less than the area of counter electrode 5.Whole three electrodes are often purified by lapping device 19.

Fig. 4 shows oxygen signal that obtains with three electrode lay-outs and the oxygen signal that can reach at present relatively, and contrast signal is to obtain with an oxygen probe of finishing by patent documentation EP144325 (S12).The oxygen signal (S12-3E) that obtains by the present invention is linear through whole possible measurement ranges from 0 to about 50mg/l.By contrast, contrast signal (S12) occurs crooked from about 15mg/l.By this good linearty, in higher measurement range, can carry out a simple calibration.

Fig. 5 shows the oxygen signal of measuring with three electrode lay-outs in a kind of solution of sulfur compound.Wherein, the concentration of sulfide keeps constant 50mg/l, and the concentration of oxygen is by 0.5 liter of 8mg/l.When using present described oxygen probe,, cause measuring-signal (S12) irrelevant with the actual oxygen content in the solution because electrode is poisoned.Otherwise surprisingly the probe signal of three electrode lay-outs (S12-3E) is so good, and is influenced as not having.

Fig. 6 shows with three electrode lay-outs at a kind of oxygen signal of measuring in the solution of surfactant that contains.When oxygen content is fixed on about 8mg/l, add anionic surfactant sodium dodecylbenzene sulfonate.When using present described oxygen probe, the influence of surfactant causes signal descend (S12).Wherein when the 50mg/l surfactant, signal departs from about 30%.A beyond thought constant measurement (S12-3E) appears in the not influence of probe display surface active agent content with three electrode lay-outs of the present invention.

Method and apparatus of the present invention is used for production process equipment and measures dissolved substance, particularly is used in the disposal system of sewage and potable water, and be used for food technology, be used for pharmaceutical technology and be used for bioengineering, and chemical enginnering process.

Essence of the present invention be by following some finished task of the present invention with flying colors:

-a system opening, that do not have barrier film in three electrode lay-outs with mechanical self-purification of voltage stabilizing,

-by the metal electrode of a current loading and produce the new possibility of essential reference potential,

The possibility of the various different electrode materials of-use,

-voltage stabilizer and measuring sonde integrated,

-be used to detect various analytes possibility and

-elimination cross sensitivity.

Claims

1. by means of an opening, aseptate survey shows that probe is used to measure the method for dissolved substance, this probe has the self-purification device of a machinery, this probe has a working electrode (4), a counter electrode (5) and a reference electrode (6), it is characterized in that, survey shows that probe is inserted in the solution of dissolved substance (2), allow an anode current flow through reference electrode (6), so that the reference potential of a cathode portion electric current when being suppressed at mixed potential formation basically and a regulation of formation, so that harmonize in accordance with regulations one arbitrarily with the polarizing voltage of freely selecting, make the detection of various analytes become possibility thus, self-purification means by machinery make electrode surface often keep active, by the horizontal influence that wire laying mode is eliminated or reduction is disturbed, dissolved substances is determined whereby.

2. by the described method of claim 1, it is characterized in that dissolved substance is gone up at working electrode (4) can play electrochemical reaction.

3. by the described method of claim 1, it is characterized in that dissolved substance is oxygen or chlorine.

4. press the application of the described method of claim 1-3, be used for being determined at production process equipment, especially the dissolved substance in the disposal system of sewage and potable water, in food technology, in pharmaceutical technology and in bioengineering and in chemical enginnering process.

5. be used to implement the device of claim 1-4 method, this device shows that by a survey opening, aseptate probe constitutes, and this probe has self-purification device and a working electrode (4), a counter electrode (5) and a reference electrode (6) of a machinery, it is characterized in that, reference electrode is to constitute whole three electrodes (4,5 by iron, zinc, silver, copper or by alloy, 6) be positioned in the same shell, and the face of electrode (4,5,6) is in same plane.

6. the device of claim 5 is characterized in that, has to be used to measure survey dissolving, that gone up the material of electrochemical reaction at working electrode (4) and to show probe.

7. by the described device of claim 6, it is characterized in that, have the survey that is used to measure dissolved oxygen DO and show probe.

8. by the described device of claim 6, it is characterized in that, have the survey that is used to measure dissolved chlorine and show probe.

9. by the described device of claim 5-8, it is characterized in that working electrode (4) is by noble metal and alloy thereof, is made of steel, graphite material, vitreous carbon or conducting polymer.

10. by the described device of claim 5-8, it is characterized in that counter electrode (5) is by noble metal and alloy thereof, is made of steel, graphite material or vitreous carbon.

11. by the described device of claim 5-10, it is characterized in that, have the self-purification means of machinery.