JPS61258157A - Method for analizing concentration of ion - Google Patents

Abstract

PURPOSE:To stabilize the characteristic of an anion selective electrode having an ion sensitive part consisting of silver halide for a long period of time by incorporating preliminarily the silver halide into a soln. which contacts with an ion sensitive membrane at the satd. concn. or above at the temp. thereof. CONSTITUTION:The silver halide is preliminarily incorporated into a sample liquid 9 to be inspected and calibration liquids 5, 6 which contact with the ion sensitive film 1' in the stage of measuring, cleaning and calibrating as well as a diluting liquid 4 held at above the temp. possessed by the liquid 4 in common use as the cleaning liquid at the satd. concn. or above at the temp. thereof in a method for analysis in which the anion selective electrode 1 having the ion sensitive membrane 1' consisting of the silver halide is used. The satd. soln. of the silver halide is thus formed from the ambient temp. conditions when the calibrating liquid for correcting the output potential from the electrode and the cleaning liquid for cleaning the flow passage for the sample to be tested arrive at the ion sensitive part, by which the elusion of the silver halide from the ion sensitive part is prevented.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an ion concentration analysis method comprising an anion-selective electrode using an ion-sensitive membrane made of silver halide.
The present invention relates to an ion concentration analysis method in which this anion-selective electrode can be used stably over a long period of time.

[Technical background of the invention and its problems]

The ion-selective electrode is the ninth type of analytical tool that selectively quantifies ions present in a liquid.
In combination with a discharge mechanism, a potential measurement mechanism, etc., it was configured as an ion concentration analyzer. The detection end of the ion-selective electrode for specific ions in the test liquid is composed of an ion-sensitive membrane. The ion-sensitive membrane is a membrane that selectively acts only on specific ions present in the liquid when the electrode is immersed in the liquid to be tested. The formed solid film type and the liquid film type formed by dispersing a substance such as a 211-toral carrier having ion selectivity in a polymeric substance are produced. Of these, the type is solid.

If the target specific ion is H, NazO.

A glass film consisting of A4203, 8102; F- is a crystal of LaF3; Ct- is a mixture 1 of ApzS and AtCt or htct. ″! Nine-liquid liquid film type.

Target specific ions are Na+, K", NH4", C2
−, crown ether in polyvinyl chloride,
It consists of dispersed palinomycin, nonactin, quaternary ammonium salt, etc. When an ion-selective electrode having such an ion-sensitive membrane is immersed in a test solution, a Nernst relationship is established between the activity of a specific ion in the test solution and the potential exhibited by the ion-selective electrode. However, the activity (a degree) of the target specific ion can be easily calculated from the measured potential of the system.

Therefore, by using an ion-selective electrode, it is possible to quantify ions in a wide range of concentrations simply by measuring the potential of the electrode, and if the electrode part is made smaller, the amount of sample liquid can be reduced. It also has the following. Due to the convenience of ion-selective electrodes as described above, they have recently been used for medical purposes, especially for Na+, Na+, and Na+ in body fluids such as blood and urine.
It is used for quantifying Ct-, etc. Many ion concentration analyzers have been devised in which ion-selective electrodes are installed in the same number of ion-selective cells as the number of target ions, and their use in the medical field, such as blood analysis, is expanding. Furthermore, a 70-cell type multi-electrode ion-selective electrode has also been devised in which a reference electrode is also incorporated and laminated and integrated for the purpose of increasing the number of target ions and reducing the amount of sample liquid.

However, such ion-selective electrodes.

During long-term use, the constituent components of the ion-sensitive membrane may be eluted into the test solution, or the harmful substances in the test solution may be absorbed, resulting in progressive deterioration of membrane activity and failure to meet the intended purpose. It does not show a potential depending on the concentration of the ion, making it impossible to quantify. For example, in the case of an anion-selective electrode using a layer made of silver halide, such as a solid membrane type ion-sensitive membrane, the ion-sensitive part, the silver halide, gradually elutes. This is because part of the layer is missing, so it does not show any Nernst response. In particular, when the test liquid is serum or blood, the silver halide layer is chipped and components such as proteins in the serum are adsorbed to the exposed silver surface, rapidly reducing ion selectivity and impairing its function. It won't flap. In the case of ion-selective electrodes installed in automatic biochemical analyzers that simultaneously analyze not only the ninth ion but also many other components, it is difficult to replace deteriorated ion-selective electrodes, as well as analyze ion concentration. In addition, there was also the uneconomical drawback that the production of the biochemical automatic analyzer itself, which had the ability to analyze many items, had to be stopped. Furthermore, in the case of small multi-item ion-selective electrodes that can perform multi-item measurements, deterioration of the anion-selective electrode made of silver halide may cause damage to other ion-selective electrodes and reference electrodes that have normal functions. This has the disadvantage of having to be replaced with a new one, and it is difficult to take advantage of the advantages of such a compact multi-item ion-selective electrode, which allows for the miniaturization of sample liquid and the ability to simultaneously measure multiple items. Ta.

[Purpose of the invention]

In view of the above points, it is an object of the present invention to provide an ion concentration analysis method capable of keeping the characteristics of an anion-selective electrode whose ion-sensitive portion is made of 7-silver halide stable over a long period of time.

[Summary of the invention]

The inventors of the present invention have conducted extensive research to achieve the above objective, and as a result, they have discovered that the loss of silver halide, which is an ion-sensitive part, is largely due to its dissolution in the solution it comes in contact with. However, when using an ion-selective electrode made of such a silver halide, the ion-selective electrode is in contact with a test sample solution, a calibration solution, a cleaning solution, etc.

If a saturated dissolved amount of silver halogenide is mixed in.

We discovered that the loss of silver halide, which is the ion-sensitive part of the ion-selective electrode, can be prevented. Since the supply amount of silver halide, that is, the saturated dissolution amount, is closely related to the temperature of the solution, the temperature of the diluting solution, calibration solution, cleaning solution, etc. to which silver halide is added is selected in advance. By keeping the temperature higher than the temperature at which it comes into contact with the ion-sensitive part of the electrode to increase its solubility, the amount of halogenated is greater than that required for the solution in contact with the ion-sensitive part to have a saturation concentration of silver halide. It was made to contain silver. Distribution of the diluent containing a sufficient amount of silver halide, the test sample solution obtained by diluting the test solution, the calibration solution for correcting the output potential from the electrodes, and the test sample. When the cleaning solution that cleans the ion-sensitive area reaches the ion-sensitive area, it becomes a saturated solution of silver halide due to the surrounding temperature conditions, which prevents the elution of silver halide from the ion-sensitive area. The life of the ion selective electrode is extended. In other words, in the proposed ion concentration analysis method, the ion-sensitive membrane is silver halide).
In the ion concentration analysis method using an anion-selective electrode, the test sample liquid comes into contact with the ion-sensitive membrane during measurement, cleaning, and calibration.

It is characterized in that silver halide is previously contained in the diluent, calibration solution, and cleaning solution, which are maintained at a temperature higher than the temperature of the calibration solution and cleaning solution, at a concentration higher than the saturation concentration at the temperature.

An example of the configuration of an analyzer according to the ion concentration analysis method of the present invention is shown in FIG. 1. This analyzer consists of an ion selective electrode (1) and a comparison electrode (2
) and a 70-cell (3); a diluent (4) which prepares a test sample solution to be sent to the flow cell and also serves as a cleaning solution; and a calibration solution-1 (5).

Calibration liquid-1 (6), flow path switching pulp pump), pump (8) that sends the diluted liquid and calibration liquid to the sample cup αυ
, a pump αI that sends the test liquid (9) before dilution to the sample cup, and a pump αη that sends the test sample liquid (9) before dilution to the sample cup, and the next test sample liquid αη prepared in the sample cup.
A pump that guides the liquid to the 70-cell and also drains the liquid from the 70-cell (one waste tank aj; ion selective electrode
1), the reference electrode (2), and the flow cell (3) are kept at the same temperature.The temperature of the diluent (4), calibration solution (5), and (6) is maintained at a temperature higher than that of the constant temperature block (a). Constant temperature block (b)? Temperature controller α to control; amplifies and amplifies the signals of the io/selective electrode (1) and the comparison electrode (2).
It is basically constructed of an amplifier (19) for calculation and its display αe.

The ion-sensitive membrane (1') of the ion-selective electrode [1] is
AfC is placed on top of AP as a pace using Ct- as a test substance.
A material with a layer of t is used. te, silver 10genide to be contained in solutions such as diluent and calibration solution.

ht corresponding to the silver halogenide contained in the ion-sensitive part
ct is used. The concentration of silver halide contained in the solution is maintained above the saturation concentration when it comes into contact with the ion-sensitive portion of the anion-selective electrode, such as silver halide. This is because the temperature of the thermostatic block (b) that keeps the diluent, calibration solution, etc. warm is maintained above the temperature of the thermostatic block (a) surrounding the ion-selective electrode by the temperature controller α4. It becomes possible. The set temperature for each of these constant temperature blocks is determined in advance by determining the relationship between the solution composition, temperature, and saturation concentration, since the saturation concentration of dino-silver halogenide and the relationship between temperature and solubility differ depending on the solution composition of the dilution solution, calibration solution, etc. Once you understand this, you can easily make a decision. For example, a tris-borate buffer solution used as a diluent when analyzing body fluids such as serum has htct'< About 2
Dissolve 4-5 X 10-' mot/l. Therefore, at the storage temperature of the buffer solution as a diluent,
It is clear that when a Ct-selective electrode in which the ion-sensing section is made of hyct is used, HTCT is eluted from the ion-sensing section and the life of the electrode is shortened because a sufficient concentration of HTCT is not supplied. Further, other dilute liquids include pure water such as ion-exchanged water. The saturation concentration of AtCL in this pure water is 0°C
, 20℃, 40℃.

At 50℃, 0.5X10, LIXIo, 2
．． 5X10, t3, 7X10-' mot/l
The same thing occurs because of the fact that At
By grasping the difference in ct saturation concentration and setting the temperature of the constant temperature block, it is possible to easily extend the life of the Ct-selective electrode made of APCt. Note that instead of containing hct in all of the diluent (4), calibration solution-I (5), and calibration solution-I (6) shown in Figure 1, diluent solution (4) Contain only in the calibration solution -! (s) *Calibration solution-1 (6) is supplied from outside the constant temperature block (b) in the same way as the test solution (9), and diluted with diluent solution (4) in a sample cup (11J) to form a calibration solution. method, or a sample cup (L
The ion concentration analysis method of the present invention can be fully utilized even with methods such as preparing a calibration solution by mixing it with the diluent (4) in 1).

[Embodiments of the invention]

Hereinafter, analysis of the chloride ion concentration in serum used as a test liquid using the ion concentration analyzer shown in FIG. 1 using the ion concentration analysis method of the present invention will be described in detail.

First, serum (9) is pumped into a predetermined amount of 50μ by pump α1.
Next, the diluent (4) is sent to the sample cup (11) by a predetermined amount of 450 μt via the flow path switching pulp (7) by the pump (8). .

In addition, this diluted solution (4) is added to ion-exchanged water at a saturation concentration (2,5
XIO-5 mol/l). In the sample cup, the serum (9) and the diluent (4) are stirred to prepare a test sample solution αη in which the components in the serum are diluted to a concentration of %.
') is set with a Ct-selective electrode αυ consisting of a layer of htct and sent to the flow cell (3). Ct at that time
- The potential difference between the selective electrode (1) and the comparison electrode (2) is sent to the display (Le) as a Ct-concentration via the amplifier (IT9) that performs amplification and calculation, and a predetermined chloride ion concentration is measured. After the measurement is completed, the test sample liquid is sent to the waste liquid tank αj.

In addition, a constant temperature block (
The set temperature of a) is 30℃, which is 10℃ lower than that of block (b).
(AfC1 saturation concentration 1.7 moi 0-5 mot/l).

After completing the measurement of the ion concentration in the serum as described above, only the diluent (4) is injected into the sample cup (11) at the ninth point before the measurement of the first serum, and this is used as a washing liquid to perform washing.

In addition, as appropriate, inject CA-1 (s) of low and high concentration calibration solutions with known concentrations into the sample cup αυ and calibrate with the diluting solution (4) in the same manner as for serum. Ct-
Calibration of the electrode sensitivity of the selective electrode and AfCl
Since the solubility of is small, it does not affect serum Ct- measurement (
One concentration of δ in 10-fold diluted serum is approximately I
10-2 m0L/l, while ion-exchanged water 40
The solubility of APCt at °C is 2.5X10-'mob
Even if a saturated solution of A is prepared, the cost is small.

Figure 2 shows that the temperature of the apparatus of Example-1 and constant temperature block (b) is not 40℃ but 20℃ lower than constant temperature block (a) by 10℃ (APC2 saturation concentration L I X 10-5 mat
/L) with the device (Comparative Example-1),
Further KIO℃ (Arcz saturation concentration 0.7 x 10-'m
The results of the life test of the silver/silver chloride electrode of the device (Comparative Example-2) set in olA) are shown.

As described above, repetition of serum analysis and washing was defined as one cycle, that is, measurement of one sample. Moreover, the sensitivity on the vertical axis in FIG. 2 is l X I O-3mo17 and I X 10-
It shows the potential difference of a 2 mol/l NaCl solution, that is, the absolute value of the slope of the Nernst response.

As is clear from FIG. 2, in Example 1, no decrease in sensitivity was observed even when more than 30,000 serum samples were analyzed, indicating good performance. On the other hand, Comparative Example-1 and Comparative Example-2
Then, the sensitivity gradually decreases. This is 1 for the device of Example-1! Whereas no elution of AtCt from the poles occurs,
In the devices of Comparative Example-1 and Comparative Example-2, the amount of k was only within the range of the AtCt saturation concentration at the temperature around the Ct-selective electrode.
AtCt is removed from the ion-sensitive membrane because tct is not supplied.
This is because the ions are gradually eluted into the sample liquid, etc., and the ion-sensing part becomes inoperable.

〔Effect of the invention〕

As detailed above, if the ion concentration analysis method of the present invention is used, deterioration of the anion-selective electrode using silver halide as an ion-sensitive membrane due to silver halide elution can be prevented and the electrode can be used for a long period of time. This allows for stable measurements.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a chloride ion concentration analyzer using the ion concentration analysis method of the present invention, and Figure 2 shows the life test results of silver/chloride steel electrodes using the ion concentration analysis method of the present invention and other methods. It is a characteristic diagram.

Claims (1)

[Claims] In an ion concentration analysis method using an anion-selective electrode in which the ion-sensitive membrane is made of silver halide, the concentration is higher than that of the test sample solution, calibration solution, and cleaning solution that come into contact with the ion-sensitive membrane during measurement, cleaning, and calibration. An ion concentration analysis method characterized in that silver halide is previously contained in the retained diluting solution, calibration solution, and cleaning solution at a concentration higher than the saturation concentration at the above-mentioned temperature.