JPH08254524A - Electrolyte concentration measuring system - Google Patents

Abstract

PURPOSE: To provide an electrolyte concentration measuring system which increases the selectivity of a chlorine-ion selective electrode and which can enhance the measuring accuracy of chlorine ions. CONSTITUTION: An electrolyte concentration measuring system is provided with a flow passage FL through which a liquid L1, to be inspected, as a measuring object and its calibration liquid L2 can be made to flow and with a flow through-type ion sensor 1 which is formed by arranging at least a chlorine-ion selective electrode 13 inside the flow passage FL. When an ion sensor 1 is driven by a controller 3, a constant-potential generation part 4 and a pump part 5, an ion concentration inside the liquid L1 to be inspected is measured by an amplification part 6, an arithmetic part 7 and an output device 8. In the system, electrodes 2a, 2b which form a pair are arranged on the upstream side and the downstream side of the chlorine-ion selective electrode 13 in the flow passage FL, and the electrodes 2a, 2b as the pair are formed of a metal, e.g. silver, which can be combined reversibly with bromine ions and iodine ions inside the liquid L1 to be inspected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte concentration measuring system used for specimen inspection and the like, and more particularly to improvement of ion selectivity of a chloride ion selective electrode arranged in a flow type ion sensor.

[0002]

2. Description of the Related Art Generally, an electrolyte concentration measuring system for measuring ion concentration (ion activity) in a sample solution such as human blood or urine is equipped with a flow-through type ion sensor,
A system is known that measures the electrolyte concentration in a sample solution based on the electromotive force generated by this ion sensor.

In the ion sensor mounted in the electrolyte concentration measuring system as described above, for example, as shown in FIG. 6, a reference electrode 102 and a plurality of ion selectivities are provided in an insulating substrate 101 having a flow passage 100 for a sample solution. Electrode 103 ... 10
5 is arranged through the insulating spacers 106 ... 106,
105 on the boundary surface (solution contact surface) between the ion-selective electrodes 103 ... 105 and the flow passage 101.
05a is provided. In this ion sensor, each of the ion sensitive substances (ion sensitive layers) 103a ... 105a has a specific ion in the sample solution, for example, sodium ion (Na ⁺ ), potassium ion (K ⁺ ), chlorine ion (C).
l ⁻ ), an electromotive force corresponding to the concentration of each ion is generated between each of the ion selective electrodes 103 ... 105 and the reference electrode 102.

Here, the ion-sensitive substance used for a plurality of ion-selective electrodes (multi-ion electrode) is, for example, a polymer film containing a crown ether derivative and valinomycin for sodium ions or potassium ions (particularly for ions). (For example, a material having a silver chloride layer on a silver electrode substrate) that is used as a chlorine ion, and has a high selectivity with respect to
Alternatively, a polymer film containing a quaternary ammonium salt is known.

[0005]

However, in the electrolyte concentration measuring system using the above-mentioned ion sensor, there is a difference in accuracy in the measured value of chlorine ion due to the inherent sensitivity characteristic of the chlorine ion sensitive substance. It was happening.

For example, general chlorine ion-sensitive substances have poor selectivity for anions other than chlorine ions, and in particular show responsiveness higher than that of chlorine ions for bromine ions and iodine ions among halogen ions. There was an occasion. For this reason, if even a small amount of these halogen ions is contained in the test liquid, the chlorine ion measurement value will increase by that much, which is the largest cause of measurement error (accuracy deviation). It was

In addition, at least chloride-sensitive substances applied to ion sensors have not been known so far, which have excellent selectivity for anions other than chloride ions and can withstand long-term use.

The present invention has been made in consideration of the above-mentioned problems of the prior art, and provides an electrolyte concentration measuring system capable of enhancing the selectivity of a chloride ion-selective electrode and improving the measurement accuracy of chloride ions. The purpose is to do.

[0009]

In order to achieve the above object, in the electrolyte concentration measuring system according to the invention of claim 1, a flow path through which a liquid sample to be measured can flow,
A flow-through type ion sensor having at least a chlorine ion-selective electrode disposed in the flow channel is provided, and the ion concentration in the liquid sample is measured by driving the ion sensor. Electrodes forming a pair are arranged on the upstream side and the downstream side of the chloride ion selective electrode, and the electrodes of the pair are made of a metal capable of reversibly combining with bromine ion and iodine ion in the liquid sample.

In the invention according to claim 2, the liquid sample contains at least a test liquid and a calibration liquid for potential calibration,
A supply means for alternately supplying the test liquid and the calibration liquid to the chloride ion-selective electrode and the pair of electrodes in the flow path is provided.

Further, in the invention according to claim 3, while the test solution is supplied to the chloride ion selective electrode and the pair of electrodes by the supplying means, the bromine ion and the iodine ion in the test solution and the metal are Means for applying a potential capable of electrochemically producing metal bromide and metal iodide to the electrode arranged on the upstream side.

Further, in the invention according to claim 4, while the calibration liquid is supplied to the chloride ion-selective electrode and the pair of electrodes by the supply means, metal bromide and metal iodide are mixed with bromine ion and iodine ion. It is provided with a means for applying an electrochemically decomposable potential to the metal to the electrode arranged on the upstream side.

Further, in the invention according to claim 5, the metal is silver.

Further, in the invention according to claim 6, the electrodes of the pair are integrally mounted on the ion sensor.

[0015]

In the electrolyte concentration measuring system according to the present invention, the paired electrodes are arranged on the upstream side and the downstream side of the chloride ion-selective electrode in the flow path, and the paired electrodes are connected to the bromine ion and the iodine ion in the liquid sample. Since it is formed of a metal that can be reversibly combined with, the bromine ion and the iodine ion in the liquid sample are electrochemically reacted with the electrode to be removed from the liquid sample. In this removed state, the chloride ion concentration in the liquid sample is measured from the electromotive force of the chloride ion selective electrode by the ion sensor.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

The electrolyte concentration measuring system shown in FIG. 1 is a system equipped with a flow-through type ion sensor 1 for electrochemically detecting a specific ion concentration in a test liquid L1 such as serum in a channel FL. This system includes metal electrodes 2a and 2b arranged in pairs on the upstream side and the downstream side of the ion sensor 1 in the flow path FL, a controller 3 for overall operation of the entire system, and a controller 3 for controlling the operation of the entire system. In response to the command, the ion sensor 1 and the metal electrodes 2a, 2
a constant potential generator 4 for applying a potential to b, and a pump unit for receiving the command from the controller 3 and alternately supplying the test liquid L1 and its calibration liquid L2 to the ion sensor 1 and the metal electrodes 2a, 2b in the flow path FL. Equipped with 5. Further, this system is provided with an amplification unit 6 for amplifying electromotive force, a calculation unit 7 for calculating ion concentration, and an output device 8 for outputting ion concentration, on the output side of the ion sensor 1.

The ion sensor 1 has a flow path F in the hollow portion of the main body.
There is a flow passage 9 forming a part of L, and both ends of this flow passage 9 are connected to the metal electrode 2 via the connecting tubes C1 and C1, respectively.
It is connected to a and 2b so as to be able to flow therethrough. In this ion sensor 1, as shown in FIG.
Three ion-selective electrodes between 10, namely a sodium ion-selective electrode 11, a potassium ion-selective electrode 12, a chloride ion-selective electrode 13, and a reference electrode 14 for reference potential.
And are installed side by side. These four electrodes 11 ... 14 are joined together with no gaps by a predetermined adhesive agent, a sealing member (not shown) such as packing, via insulating spacers 15.

Of these, each of the ion selective electrodes 11 ... 13 has plate-shaped conductors 11b ... 13b in the insulating electrode bodies 11a.
13b is provided with an ion sensitive layer 11c ... 13c which is electrochemically connected to one end (flow passage) side of 13b and is made of a predetermined sensitive substance prepared for each ion. Here, the other ends of the plate conductors 11b ... 13b have lead wires 11d.
It is electrically connected to the amplification unit 5 via d. The ion-sensitive layers 11c ... 13c form a part of the inner wall of the flow passage 11 and are in contact therewith with the solution in the flow path FL.

The reference electrode 14 has a recess 14a provided in one of the insulating substrates 9 (on the side of the chloride ion selective electrode),
It is formed of an electrolyte solution (for example, potassium chloride) 14b sealed in the recess 14a, and a conductor 14c having one end immersed in the electrolyte solution 14b. The other end of the conductor 14c is electrically connected to the amplification unit 6 and the constant potential generation unit 4 via the lead wire 14d.

The metal electrodes 2a and 2b are, as shown in FIG. 2, a flow passage 20 which forms a part of the flow path FL in the hollow portion of the main body.
Electrode bodies 21a, 21 that have a and 20b and form a main body
Plate-shaped silver electrodes 22a and 22b are provided in b. One end of each of the silver electrodes 22a and 22b forms a part of the inner wall of each of the flow passages 20a and 20b, and is in contact therewith with the solution in the flow path FL, while the other end thereof is connected to the constant potential generating portion via the lead wires 23a and 23b. 4 is connected. Among these, the inflow side of the flow passage 20a of the upstream metal electrode 2a is communicatively connected to the liquid inflow tube C2, and the outflow side of the downstream metal electrode 2b is communicable to the liquid outflow tube C3. It is connected.

The controller 3 is composed of, for example, a microcomputer having a CPU, and the processing (see later) of the microcomputer determines the operation start time and the operation end time of the constant potential generator 3 and the pump unit 4 to give a command. give.

The constant potential generator 4 is composed of, for example, a constant voltage power supply circuit, and receives a command from the controller 3 to set preset potentials Va and Vb (see later) to the comparison electrode 14 to the upstream side of the ion sensor 1. Arranged metal electrode 2a
Give to.

The pump section 5 is provided with a drive source 51 for generating power, which operates in response to a command from the controller 3, a piston 52 for receiving power from the drive source 51, and a cylinder 53 for the piston 52. . This cylinder 53
Since the suction port of is connected to the inside of the liquid outflow tube C3 through the expansion valve 54, the inside of the liquid outflow tube C3 is decompressed by the piston operation in the cylinder 53.
As a result, the test liquid L1 in the cell Ce and its calibration liquid L
2 is a liquid inflow tube C2 and an upstream metal electrode 2a
And is supplied to the ion sensor 1 via the connecting tube C1 and is discharged from the ion sensor 1 to the liquid outflow tube C3 via the connecting tube C1 and the metal electrode 2b on the downstream side.

The amplification section 6 is a preamplifier 6a to which the electromotive force generated between the ion selective electrodes 11 ... 13 and the comparison electrode 14 in the ion sensor 1 is individually input for each channel.
.. 6a, each preamplifier 6a ... 6a amplifies each electromotive force, and outputs each amplified signal to the arithmetic unit 7 of the next stage via an A / D, an interface, etc. (not shown).

The calculation unit 7 is composed of, for example, a microcomputer having a CPU, a memory and the like, and by the processing of the microcomputer, data relating to a calibration curve previously held in a storage device such as a memory and each amplification from the amplification unit 6. Based on the signal, each ion concentration is calculated, and the calculated concentration data is output to the output device 7 via an interface or the like (not shown).

The output device 7 is composed of a monitor, a printer or the like, and displays the density data from the arithmetic unit 7 on a screen or prints it out.

Now, the principle of the electrolyte measuring system according to the present invention will be described with reference to FIG.

FIG. 3 is chlorine present in solution, bromine and three halogen ion iodine (Cl ^-, Br ^-,
I ^-) and reversible electrochemical reaction (electron transfer reaction between the silver electrode in the same solution) illustrates the. Each of the three current-potential curves shown in the figure is a silver electrode when a potential (E / V) with respect to a reference potential (standard hydrogen electrode (NHE)) is variably applied to one of the paired silver electrodes. It shows the change in the current value (i) of the electromotive force that occurs during the period. It rises linearly from the low level state (that is, the stable state of each halogen ion) in which the current value is almost constant as the potential rises. Change to a constant high level state (ie, the stable state of each silver halide). However, for the three halogen ions, the potential range from the vicinity of the rise of the current level in the current-potential curve to the vicinity of the arrival of the high level is higher in the order of iodine, bromine, and chlorine, and overlaps. Not not.

Therefore, the potential applied to the silver electrode is changed from near the high level of the current value in the current-potential curve of bromine ion (ie, the stable state of both silver iodide and silver bromide) to the current in the current-potential curve of chloride ion. By setting the potential range Va (see the shaded area in the figure) just before the high level rise of the value (that is, the stable state of chlorine ion), the silver having the potential applied with the bromine ion and iodine ion in the solution Silver bromide and silver iodide can be produced electrochemically from the electrodes. Moreover, during this production reaction, chlorine ions in the solution remain in a stable state. Therefore, it is possible to selectively remove only the bromine ion and the iodine ion, which are the main factors of the accuracy deviation of the conventional chloride ion selective electrode, from the solution as silver halide on the electrode surface portion.

Further, in order to restore the silver halide thus generated on the electrode surface to the original halogen ion and metal, the potential applied to the silver electrode is set near the high level rise of the current value in the current potential curve of bromine ion. May be set to a low potential range Vb.

Focusing on the electrochemical characteristic (reversible binding reaction relationship) between the halogen ion and the metal electrode as described above, in the electrolyte concentration measuring system according to the present embodiment, the reference potential of the reference electrode 14 is used. On the other hand, the potential applied to the upstream metal electrode 2a was set based on the potential ranges Va and Vb.

Now, returning to the embodiment, the overall operation will be described.

First, before measuring the concentration of the test liquid L1, various ion concentration known solutions (calibrators), for example, calibrators of relatively high concentration and low concentration are respectively set and the ion sensor 1 is activated. As a result, the concentration of each ion in the calibrator is measured, the calculation unit 7 creates data relating to the calibration curve for ion concentration conversion based on the measured value, and the data is held in advance.

Next, the cell Ce containing the test liquid L1 is set and the ion sensor 1 is activated. At the time of this activation, the controller 2 gives an operation start command to the pump unit 5 and gives an application start command to the constant potential generation unit 4.
As a result, the test liquid L1 in the cell is transferred to the metal electrodes 2a and 2b.
And the potential Va with respect to the reference potential of the comparison electrode 14 is applied to the metal electrode 2a on the upstream side while being supplied to the ion sensor 1. Since the potential Va is set in the range where bromine ions and iodine ions are oxidized to silver bromide and silver iodide as described above, silver is not present on the silver electrode surface of the upstream metal electrode 2a. By combining with bromine ion and iodine ion in the test liquid L1,

[Formula 1] Ag + Br ⁻ → AgBr + e (1)

[Number 2] ^{Ag + I - → AgI + e} ...... (2) silver bromide and silver iodide by reaction formula is generated, a current flows between the metal electrodes 2a and 2b form a pair. Therefore, bromine ions and iodine ions in the test liquid L1 are removed from the test liquid L1 by the metal electrode 2a before reaching the ion sensor 1. Next, the controller 2 gives an operation stop command to the pump unit 5, whereby the supply of the test liquid L1 is stopped. In this state, measurement of each ion concentration of the test liquid L1 is started. That is, the electromotive force of each of the ion selective electrodes 11 ... 13 is amplified by the amplification unit 6, and the amplified signal is converted into an ion concentration by the calculation unit 7 and output to the output device 8.

Next, when the cell Ce containing the calibration liquid L2 is replaced with the cell Ce containing the test liquid L1 and set, the controller 2 gives an operation start command to the pump unit 5 and at the same time to the constant potential generating unit 4. It gives a potential application command. As a result, the calibration liquid L2 in the cell Ce is supplied to the silver electrodes 2a and 2b and the ion sensor 1, and the metal electrode 2 on the upstream side is also supplied.
The potential Vb for the comparison electrode 14 is applied to a. As described above, this potential Vb is set in the range in which silver bromide and silver iodide are oxidized to bromine ions and iodine ions in advance, so that between the calibration liquid L2 and the upstream metal electrode 2a, ( The silver bromide and silver iodide formed on the surface of the silver electrode in 1) and (2) are

[Number 3] ^{AgBr + e → Ag + Br -} ...... (3)

Equation 4] AgI + e → Ag + ^I - is reduced to silver and bromine ions and iodine ions by reaction formula ... (4). Therefore, bromine ions and iodine ions are released into the calibration liquid L2.

Here, when a required time (for example, about ½ of the time from the operation start to the stop) elapses from the operation start of the pump unit 5, the controller 2 gives the constant potential generating unit 4 an application stop command. As a result, the potential application is stopped before the supply of the calibration liquid L2 is stopped, and the bromine ions and iodine ions released into the calibration liquid L2 are washed out from the ion sensor 1 via the upstream metal electrode 2a. At the same time, the calibration liquid L2 also calibrates the potentials of the respective ion-selective electrodes 11 ... This potential calibration is performed for each test liquid L1 in order to suppress a measurement error during continuous measurement.

As described above, by alternately applying the preset potentials for the test solution and the calibration solution to the metal electrode on the upstream side (front side of the flow path) of the ion sensor in the flow path, the test solution The bromine and iodine ions in the solution are removed before reaching the chloride-selective electrode, and after measuring the concentration of the test solution, silver bromide and silver iodide on the metal electrode are dissociated into halogen ions in the calibration solution. Washed away.

Therefore, by using a chloride ion-selective electrode using a general sensitive material, it is possible to almost avoid the error of the chloride ion measurement value due to the involvement of conventional bromine ion and iodine ion, and the reliability of the entire system is greatly improved. Come to do. Secondly, each ion-selective electrode of the ion sensor,
In particular, the service life of the chloride ion-selective electrode is improved, and the metal electrode can be continuously and repeatedly used without replacement. Moreover, since the metal electrode has a separate structure from the ion sensor, the conventional ion sensor can be used as it is.

Although the ion sensor and the metal electrode are separately provided in the above embodiment, the present invention is not necessarily limited to this structure. For example, as shown in FIG. 4 and FIG.
The structure may be integrated with the ion sensor. In this case, in the ion sensor 1a shown in FIG. 4, the paired metal electrodes 2a, 2b are arranged immediately before and after the chloride ion selective electrode 13, and in the ion sensor 1c shown in FIG. 5, the paired metal electrodes 2a, 2b are arranged. 2b is provided at a position sandwiching the chloride ion selective electrode 13 and the reference electrode 14. Further, the paired metal electrodes may be arranged at positions sandwiching the chloride ion-selective electrode and the other ion-selective electrode, and the point is that they are arranged on the upstream side and the downstream side of the chloride ion-selective electrode, respectively. Good.

Although the metal electrode is formed of a silver electrode in the above embodiment, the present invention is not necessarily limited to this, and the electrochemical characteristics described in the above principle (see FIG. 3) are used. Any metal may be used as long as it has a property of being capable of reversibly combining with halogen ions.

Furthermore, in the above embodiment, the test liquid and its calibration liquid are set manually, but the present invention is not necessarily limited to this, and for example, a container (cell) equipped with a moving mechanism. It may be configured to be automatically set by using an on-board device. In this case, for example, a sequence may be set in advance in the controller to alternately supply the test liquid and the calibration liquid, and the container mounting device may be operated together with the pump unit and the constant potential generating unit according to this sequence.

In the above embodiment, the ion sensor is provided with each ion selective electrode for sodium ion and potassium ion. However, the present invention is not necessarily limited to this, and at least a chloride ion selective electrode is provided. Anything is acceptable.

[0044]

As described above, in the electrolyte concentration measuring system according to the present invention, the paired electrodes are arranged on the upstream side and the downstream side of the chloride ion selective electrode in the flow path, and the electrodes of the pair are arranged. Since it is formed of a metal that can reversibly combine with bromine ion and iodine ion in the liquid sample, bromine ion and iodine ion in the liquid sample are electrochemically reacted with the electrode to be removed from the liquid sample. The selectivity of the chloride ion-selective electrode in the ion sensor can be increased, and the measurement accuracy of chloride ions is significantly improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrolyte concentration measuring system according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a main part of a metal electrode and an ion sensor.

FIG. 3 is a current / potential graph for explaining the principle of the electrolyte concentration measuring system according to the present invention.

FIG. 4 is a schematic cross-sectional view of an ion sensor for explaining an application example of an integrated structure of a metal electrode and an ion sensor.

FIG. 5 is a configuration diagram of a main part of an electrolyte concentration measuring system for explaining an application example of an integrated structure of a metal electrode and an ion sensor.

FIG. 6 is a schematic cross-sectional view of an ion sensor according to a conventional electrolyte concentration measuring system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ion sensor FL flow path 2a, 2b metal electrode 3 controller 4 constant potential generation part 5 pump part 6 amplification part 7 calculation part 8 output device 9 flow passage (ion sensor) 10 insulating substrate 11 sodium ion selective electrode 12 potassium ion selection Electrode 13 Chloride-selective electrode 11a, 12a, 13a Electrode body 11b, 12b, 13b Plate-shaped conductor 11c, 12c, 13c Ion-sensitive substance 11d, 12d, 13d, 14d, 23a, 23b Lead wire 14 Reference electrode 14a Recess 14b Electrolyte solution 14c Conductor 15 Insulating spacer Flow path 20a, 20b Flow path (metal electrode) 21a, 21b Electrode body 22a, 22b Silver electrode

Claims (6)

[Claims] 1. A flow channel through which a liquid sample to be measured can flow, and a flow-type ion sensor in which at least a chlorine ion-selective electrode is arranged in the flow channel, and the ion sensor is driven. In the electrolyte concentration measuring system for measuring the ion concentration in the liquid sample by arranging the electrodes forming a pair on the upstream side and the downstream side of the chloride ion-selective electrode in the flow path, respectively, the electrode of the pair is the liquid state. An electrolyte concentration measuring system characterized by being formed of a metal capable of reversibly combining with bromine ion and iodine ion in a sample. 2. The liquid sample contains at least a test solution and a calibration solution for potential calibration, and the test solution and the calibration solution are alternately supplied to a chloride ion selective electrode and a pair of electrodes in the flow channel. The electrolyte concentration measuring system according to claim 1, further comprising a supply unit. 3. The metal bromide and iodine are extracted from the bromine ion and iodine ion in the test solution and the metal while the test solution is supplied to the chloride ion-selective electrode and the pair of electrodes by the supply means. The electrolyte concentration measuring system according to claim 2, further comprising means for applying a potential capable of electrochemically generating a metal oxide to the electrode arranged on the upstream side. 4. The metal bromide and metal iodide electrochemically react with bromine ion and iodine ion and the metal while the calibration liquid is supplied to the chloride ion selective electrode and the pair of electrodes by the supply means. The electrolyte concentration measuring system according to claim 2, further comprising means for applying a potential that can be decomposed into the electrode to the electrode arranged on the upstream side. 5. The electrolyte concentration measuring system according to claim 1, wherein the metal is silver. 6. The electrolyte concentration measuring system according to claim 1, wherein the pair of electrodes are integrally mounted on the ion sensor.