JP4583937B2 - Method for electrochemical measurement of arsenic ions - Google Patents

Description

  The present invention relates to an electrochemical measurement method for arsenic ions.

  In recent years, as a technique for measuring the arsenic ion concentration in an aqueous solution, a method for measuring the total amount of trivalent arsenic ions and pentavalent arsenic ions by using an atomic absorption spectrometer, HPLC-ICP / MS, or the like has been established. However, there is a problem in that the analyzer is expensive and takes time for pretreatment and measurement.

  On the other hand, rapid testing methods such as water quality test pack test and diethylcarbamic acid method have been established as inexpensive analytical means, but these measurement methods are only detection sensitivity to the extent that they are used for screening. It does not necessarily contain medicinal poisons that have become positive by the rapid test method, and confirmation analysis using a plurality of test methods including instrumental analysis is required.

  Furthermore, an electrochemical measurement method is also adopted as a quick and simple analytical means, but the electrochemical measurement method can be quickly measured only with trivalent arsenic ions, but is known as an electrochemically inactive species. It was not possible to measure pentavalent arsenic ions.

Therefore, in order to measure pentavalent arsenic ions, a redundant pretreatment process for reducing pentavalent arsenic ions to trivalent arsenic ions is necessary, and the speed that is the merit is lost. (For example, refer nonpatent literature 1).
Anal Chem (1982) 311: 187-191

  An object of the present invention is to provide an electrochemical measurement method capable of measuring trivalent arsenic ions and pentavalent arsenic ions in an aqueous solution quickly and easily at low cost in view of the above-mentioned drawbacks.

  The method for electrochemical measurement of arsenic ions according to claim 1, wherein an electrode is brought into contact with an aqueous solution in which arsenic ions and an electron mediator that binds to arsenic ions coexist or are in contact with each other. And measuring an oxidation current value of arsenic ions flowing in the substrate.

  The electron mediator is a compound that binds to arsenic ions and allows the arsenic ions to be measured by an electrochemical measurement method. Therefore, the electron mediator is preferably a compound that binds to a pentavalent arsenic ion that cannot be measured by conventional electrochemical measurement methods and becomes electrochemically active.

As the electron mediator, a compound having a thiol group capable of binding to an arsenic ion is preferable. For example, salts such as D-cysteine, L-cysteine, racemic cysteine, cysteine hydrochloride, D-homocysteine, L-homo Cysteine, racemate of homocysteine, DN-acetylcysteine, LN-acetylcysteine, racemic form of N-acetylcysteine, other N-substituted cysteines and salts thereof, L-cysteine methyl ester, other esterified cysteine and its Cysteine such as salts; aminobenzenethiol, aminoethanethiol, benzenedithiol, butanethiol, butanedithiol, propanethiol, propanedithiol, ethanethiol, ethylenedithiol, dodecanethiol and the like.

  In addition, as an electron mediator, the peak of the oxidation current value of the complex bonded to the arsenic ion when measured by the electrochemical measurement method has a new oxidation potential that does not interfere with the peak of each of the arsenic ion and the electron mediator alone. However, cysteine which is water-soluble and does not require the addition of an organic solvent at the time of measurement and which does not require any special treatment at the time of disposal is preferably used.

  The content of the electron mediator is not particularly limited, but it is contained in a large excess with respect to the pentavalent arsenic ion so that the electron mediator and the pentavalent arsenic ion are all combined in the quantitative analysis. It is preferable.

  In the method for electrochemical measurement of arsenic ions according to claim 1, when arsenic ions and a mediator that binds to arsenic ions are dissolved in water, both exist in a coexisting state or in a combined state in water. Therefore, the electrode is brought into contact with the aqueous solution in that state, and the oxidation current value of arsenic ions flowing through the electrode in contact with the aqueous solution is measured.

  An electrochemical measurement method is a method in which an electrical signal is applied to a substance to be detected to cause a chemical reaction by applying a potential between electrodes or by passing a current between electrodes, or from a response signal. In this invention, the oxidation current value of arsenic ions is measured.

Examples of the electrochemical measurement method include a voltammetry method, a stripping voltammetry method, an amperometry method, a potentiometry method, and a Coulomb measurement method.
Examples of the voltage and current waveforms applied in these electrochemical measurement methods include a pulse wave, a differential pulse wave, a triangular wave, and a step wave as appropriate.

  In the voltammetry method, a potential is applied between the working electrode and the reference electrode, and the relationship between the current flowing at that time and the applied potential is examined. The electrode used in the voltammetry method is preferably a three-electrode system in which a reference electrode is added to the working electrode and the counter electrode. Since the reference electrode always shows a constant potential regardless of the magnitude of the applied potential, using the reference electrode as a reference is useful for determining the absolute value of the potential applied to the working electrode.

  The above stripping voltammetry method is to apply a potential suitable for reduction of a detected substance to the working electrode to concentrate the reduced substance of the detected substance on the working electrode, and then to apply a potential suitable for the oxidation of the detected substance. This is a technique for desorbing the reduced form of the substance to be detected from the working electrode.

  At this time, since desorption occurs at a potential specific to the substance to be detected, the type of the substance to be detected can be specified, and the concentration of the substance to be detected can be specified by measuring the current that occurs at the same time. . Since it includes a step of concentrating the reduced form of the substance to be detected on the working electrode, a more sensitive analysis is possible. Also in this measurement method, in order to know the absolute potential, a three-electrode system including a working electrode, a counter electrode, and a reference electrode is desirable. Of the stripping voltammetry methods, the linear sweep voltammetry method or the square web voltammetry method is preferred.

  The amperometry method is a measurement method in which a constant potential is applied between a working electrode and a reference electrode, and a change in current with time is monitored. Also in this measurement method, in order to know the absolute potential, a three-electrode system including a working electrode, a counter electrode, and a reference electrode is desirable.

  The potentiometric method is a measurement method in which an appropriate current is passed between the working electrode and the counter electrode, and the potential change at that time is monitored. Also in this measurement method, in order to know the absolute potential, a three-electrode system including a working electrode, a counter electrode, and a reference electrode is desirable.

  In the coulometry method, a substance to be detected is electrodeposited by applying a potential between a working electrode and a reference electrode, and the amount of coulomb is measured.

  The material of the working electrode is not particularly limited, but is required to be a material that is not corroded or oxidized by arsenic ions or a solvent thereof, a dispersion medium, dissolved oxygen, or the like. In general, an electrode of any material adsorbs hydrogen ions on the surface of the electrode on the negative potential side and forms an oxygen film on the positive potential side. Since the conductivity is different, this state is not preferable as an electrode used for electrochemical measurement.

  Therefore, it is better that the potential difference (= potential window) between the potential for forming the hydrogen ion film and the potential for forming the oxide film is wider, and it is preferable to use a metal species satisfying such a condition as an electrode material. , Platinum, gold, mercury, silver, bismuth and the like, and gold having good compatibility with the electron mediator is preferable.

  The structure of the working electrode is not particularly limited, but it is possible to increase the material diffusion speed on the working electrode of the substance to be detected by miniaturizing the electrode area, that is, the structure generally called a microelectrode. Can do.

  The material of the counter electrode is not particularly limited, but is required to be a material that is not subject to corrosion or oxidation by the substance to be detected or its solvent, dispersion medium, dissolved oxygen, etc., and platinum is preferably used.

  The reference electrode needs to have a stable electric potential, and examples thereof include a hydrogen electrode, a saturated calomel electrode (= mercury / mercury chloride electrode), a silver / silver chloride electrode, and the versatility and processing of materials. From the viewpoint of cost, a silver / silver chloride electrode is preferred.

  When performing electrochemical measurement, it is preferable to measure the oxidation current value associated with the potential change using a potentiostat. As the measurement method, a stripping voltamin that can obtain a current value corresponding to the stripping potential is used. The measurement method is preferable, and the linear sweep voltammetry method or the square web voltammetry method is particularly preferable.

  The method for electrochemical measurement of arsenic ions according to claim 2, wherein an electron mediator that binds to arsenic ions is added to an aqueous solution containing arsenic ions, and the arsenic ions and the electron mediator coexist or exist in a combined state. Further, the present invention is characterized in that an oxidation current value of arsenic ions flowing through the electrode in contact with the aqueous solution is measured.

  Hereinafter, the points different from the first aspect will be mainly described.

  3. The method for electrochemical measurement of arsenic ions according to claim 2, wherein an electron mediator that binds to arsenic ions is added to an aqueous solution containing arsenic ions so that the arsenic ions and the electron mediator coexist or are combined. An aqueous solution is obtained.

A method of adding an electron mediator that binds to arsenic ions to an aqueous solution containing arsenic ions is not particularly limited, and any known method may be employed. For example, an electron mediator is added to a 1M hydrochloric acid aqueous solution containing arsenic ions. The method of adding and dissolving is mentioned.

  The method for electrochemical measurement of arsenic ions according to claim 3, wherein an aqueous solution containing arsenic ions is allowed to act on a carrier that adsorbs arsenic ions, and then an eluent containing an electron mediator that binds to the arsenic ions acts on the carrier. The electrode is brought into contact with the obtained eluent, and the oxidation current value of arsenic ions flowing through the electrode in contact with the eluent is measured.

The carrier is not particularly limited, and any carrier conventionally used as a chromatographic adsorption carrier can be used, and may be in any form of a film, a fine particle, and a porous body, A combination of these may be used.
Below, each form is demonstrated concretely.

  A carrier having a membrane structure is mainly formed of a fiber in a filter shape. An anion exchange membrane, a polymer membrane, or a metal membrane may be formed with appropriate holes. Examples of membrane structures include those that have an adsorption function for the substance to be measured depending on the form of the surface, those that have the same adsorption function by modifying the surface with functional groups, and particles having a specific function carried on the fiber Things.

  The fine particles include those having a function to adsorb the substance to be measured depending on the form of the fine particle surface and those having a similar adsorption function by modifying the surface of the fine particle with a functional group. Chromatography can be performed if the fine particles are packed in a column shape extending about 10 mm or more in the longitudinal direction of the flow path. The filling shape may be either a rectangular parallelepiped shape or a cylindrical shape.

  The porous body is a carrier having a large number of communication holes. Examples thereof include a monolithic porous inorganic material such as porous ceramic and porous glass, a polyacrylamide gel, a styrene divinylbenzene copolymer and the like made porous.

  Some have a function of adsorbing a substance to be measured depending on the form of the surface of the communication hole, and others have the same adsorption function by modifying the surface of the communication hole with a functional group. When the carrier having the communication hole has a monolithic structure, it is called “monolith”.

  When the length is smaller than the length that can be chromatographed, it is called a monolith disc, and the length that can be chromatographed is called a monolith column, and the terminology is properly used according to the purpose.

  Monolithic columns can pass at relatively low pressure compared to resin-filled columns, so low-pressure liquid feed pumps can be used, and equipment with the same analytical performance is smaller and consumes less power. Electricity is possible.

  Monolithic discs can also be supplied at low pressure for the same reason, so that the size of the device can be easily reduced. Since both the monolith column and the monolith disk have an integrated structure, they are easy to handle when installed in a cartridge type microreactor.

  Examples of the material constituting the carrier include styrene-divinylbenzene copolymer, polymethacrylate resin, polyhydroxymethacrylate resin, polyvinyl alcohol, polyethylene, polypropylene, ethylene-propylene copolymer, and other polyolefins, ethylene-tetra Olefin-halogenated olefin copolymer represented by fluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, halogenated polyolefin represented by polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, etc. And polysulfone, silica, alumina and the like.

  In the case of fibrous carriers, cellulosic materials, vegetable fibers such as cotton and hemp, various natural fibers typified by animal fibers such as silk and wool, various fibers such as polyester fibers and polyamide fibers Fibrous materials such as synthetic fibers are used.

  Even when the above structure is not adopted, if the wall surface of the flow path has an adsorption function for the substance to be measured, a concentration function can be similarly produced. In order to give the surface of the support an adsorption function for arsenic, the surface has a complementary structure to arsenic, or an ionic bond, coordination bond, chelate bond, hydrophobic interaction, interaction due to intramolecular polarity, etc. It is only necessary to fix the functional molecule that causes

  Examples of the functional molecule having an interaction include a sulfo group, a quaternary ammonium group, an octadecyl group, an octyl group, a butyl group, an amino group, a trimethyl group, a cyanopropyl group, an aminopropyl group, a nitrophenylethyl group, and a pyrenylethyl group. Group, diethylaminoethyl group, sulfopropyl group, carboxyl group, carboxymethyl group, sulfoxyethyl group, orthophosphoric acid group, diethyl (2-hydroxypropyl) aminoethyl group, phenyl group, iminodiacetic acid group, ethylenediamine, sulfur atom Chelate-forming groups such as various functional groups such as mercapto groups, dithiocarbamic acid groups, thiourea groups, avidin, biotin, gelatin, heparin, lysine, nicotinamide adenine dinucleotide, protein A, protein G, phenylalanine, and castor Merekuchin, dextran sulfate, adenosine 5 'phosphate, glutathione, ethylenediamine diacetic acid, Procion red, aminophenyl boronic acid, bovine serum albumin, polynucleotides (e.g. DNA), protein atomic groups such as (e.g., antibody) and the like. These may be used alone or in combination of two or more.

  Specific examples of the carrier include Empore (TM) disk cartridge available from 3M under the Anion-SR trademark, and 1M hydrochloric acid (pH ≦ about 2) can be used as an eluent.

  This carrier is obtained by fixing fine particles having a particle diameter of 50 to 100 μm to fibrous polytetrafluoroethylene to form a film having a thickness of 0.5 to 0.75 mm, and the fine particle surface is modified with a quaternary amine group. ing.

  Some carriers need to be passed through a liquid that activates the carrier before allowing the sample liquid to pass through. For example, a quaternary amine that adsorbs arsenic, selenium, and hexavalent chromium exhibits an adsorption performance when it comes into contact with a hydroxide ion. This is because a target anion replaces a hydroxide ion. The reaction is used. In this case, a carrier activation solution is used. As the carrier activation liquid, sodium hydroxide, potassium hydroxide or the like is used.

  The size of the carrier can be freely determined as long as the adsorption capacity of the carrier does not become saturated when adsorbing the target component. The size of the carrier is determined by assuming in advance how much a substance that can be adsorbed on the carrier is contained in the solution containing the substance to be measured.

  If the adsorption capacity of the carrier is small, it is easy to increase the concentration factor, but it is likely to be saturated adsorption, so it is necessary to make the carrier large enough to obtain the desired adsorption capacity. In addition, when a chromatographic action is expected in the adsorption part, it is necessary to form a column shape having a length of at least 10 mm in the flow path direction.

The porosity of the carrier, the size of the communication hole, and the like are determined in such a range that the contact with the solution can be reliably performed and clogging does not become a problem. In the case of a membrane structure, the coarseness of the mesh is preferably about 0.3 μm or more. When fine particles are used, the particle diameter is preferably about 2 to 50 μm, and the communication hole in the case of a monolith column is preferably about 1 to 50 μm.

  The above eluent is for separating the arsenic ions adsorbed on the carrier from the carrier, and the effective eluent differs depending on the form of adsorption. A suitable eluent may be selected.

  For example, a solution containing ions that are easily adsorbed on the surface of the carrier, and when the solution passes through the carrier, the component to be measured in the form of ions already adsorbed on the carrier is exchanged with ions in the eluent. As a result, the component to be measured can be released from the carrier.

  The method for electrochemical measurement of arsenic ions according to claim 3, wherein an aqueous solution containing arsenic ions is allowed to act on a carrier that adsorbs arsenic ions to be adsorbed, and then an eluent containing an electron mediator that binds to the arsenic ions is used. The arsenic ions are released by acting on the carrier.

  Therefore, in the obtained eluent, arsenic ions and electron mediators that bind to arsenic ions exist in a coexisting state or in a combined state. Therefore, the arsenic ions flowing into the electrode in contact with the eluent are in contact with each other. The oxidation current value is measured.

  For example, an aqueous solution containing arsenic ions is passed through an anion exchange membrane, arsenic ions are adsorbed on the anion exchange membrane, and then an eluent containing an electron mediator (for example, 1M hydrochloric acid-1.5M L-cysteine solution) is added. The electrode is brought into contact with the eluent in which the arsenic ions and the electron mediator (L-cysteine) obtained coexist with each other and are present in a coexisting state or in a combined state. The oxidation current value of the arsenic ions flowing through is measured.

  The method for electrochemical measurement of arsenic ions according to claim 7, wherein an electrode containing an electron mediator that binds to arsenic ions is brought into contact with an aqueous solution containing arsenic ions, and an oxidation current value of arsenic ions flowing through the electrode in contact with the aqueous solution Is measured.

  The electrode containing an electron mediator that binds to arsenic ions is an electrode that contains an electron mediator that binds to arsenic ions. Generally, an electron mediator that binds to arsenic ions adheres to the surface of the electrode. Electrode.

  The method for producing the electrode is not particularly limited, and may be produced by any conventionally known method. For example, an electrolytic solution in which an electron mediator is dissolved (for example, 1M hydrochloric acid-1.5M L-cysteine solution) And an electrode are brought into contact with each other, an electric potential is applied to the electrode, and an electron mediator (L-cysteine) is adsorbed on the electrode surface.

  As the electrode, the electrode described above is used, but an electrode made of gold is preferable, and a cysteine-containing gold electrode is particularly preferable.

  The structure of the electrochemical measurement method for arsenic ions according to claim 1 is as described above, and an electrode is brought into contact with an aqueous solution in which arsenic ions and an electron mediator that binds to arsenic ions coexist or are combined. Since the oxidation current value of arsenic ions flowing through the electrode in contact with the aqueous solution is measured, arsenic ions can be measured quickly and easily at low cost by an electrochemical measurement method.

  The structure of the electrochemical measurement method for arsenic ions according to claim 2 is as described above, wherein an electron mediator that binds to arsenic ions is added to an aqueous solution containing arsenic ions, and the arsenic ions and the electron mediator coexist. Since the electrode is brought into contact with the aqueous solution present in the bonded state, and the oxidation current value of the arsenic ions flowing through the electrode in contact with the aqueous solution is measured, the arsenic ions can be measured quickly and easily at low cost by the electrochemical measurement method. Can be measured.

  The structure of the electrochemical measurement method for arsenic ions according to claim 3 is as described above, and includes an electron mediator that binds to arsenic ions after an aqueous solution containing arsenic ions is allowed to act on a carrier that adsorbs arsenic ions. The eluent is allowed to act on the carrier, the electrode is brought into contact with the obtained eluent, and the oxidation current value of the arsenic ions flowing through the electrode in contact with the eluent is measured, so that arsenic ions can be concentrated. The electrochemical measurement method enables high-precision, low-cost, quick and simple measurement.

  The structure of the electrochemical measurement method for arsenic ions according to claim 4 is as described above, and the electron mediator is an electron mediator that binds to pentavalent arsenic ions. Can be measured quickly and easily at low cost. In addition, trivalent arsenic ions and pentavalent arsenic ions can be measured at the same time, or can be separately measured by valence.

  The structure of the electrochemical measurement method for arsenic ions according to claim 5 is as described above, and since the electron mediator is a compound having a thiol group, both trivalent arsenic ions and pentavalent arsenic ions are used. Can be measured more accurately and quickly at a low cost.

The structure of the electrochemical measurement method for arsenic ions according to claim 6 is as described above. Since the compound having a thiol group is cysteine, the peak of the oxidation current value of the complex bonded to cysteine and arsenic ions is arsenic. Arsenic ions can be measured quantitatively and accurately because they have new oxidation potentials that do not interfere with the peaks of ions and cysteine alone.
Cysteine is water-soluble, and it is not necessary to add an organic solvent at the time of electrochemical measurement, and no special treatment is required at the time of disposal.

  The structure of the electrochemical measurement method for arsenic ions according to claim 7 is as described above. An electrode containing an electron mediator that binds to arsenic ions is brought into contact with an aqueous solution containing arsenic ions, and the aqueous solution is brought into contact with the electrode. Because it measures the oxidation current value of flowing arsenic ions, it is not necessary to dissolve the electron mediator that binds to arsenic ions in an aqueous solution containing arsenic ions. And it can measure simply.

  The structure of the electrochemical measurement method for arsenic ions according to claim 8 is as described above, and the electrode including an electron mediator that binds to arsenic ions is a cysteine-containing gold electrode. High accuracy, low cost, quick and simple measurement.

  The structure of the electrochemical measurement method for arsenic ions according to claim 9 is as described above, and since the electrochemical measurement method is a stripping voltammetry method, arsenic ions can be measured quantitatively and accurately. .

  The structure of the electrochemical measurement method for arsenic ions according to claim 10 is as described above, and the stripping voltammetry method is a linear sweep voltammetry method or a square web voltammetry method. It can be measured quantitatively and accurately.

  Next, examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1
FIG. 1 is a schematic diagram showing an electrochemical measurement apparatus used in Example 1. FIG. In the figure, 1 is a working electrode which is a gold electrode, 2 is a reference electrode which is a silver-silver chloride electrode, and 3 is a counter electrode which is a platinum wire.

A glass cell container 5 is supplied with a sample aqueous solution {1N hydrochloric acid solution of L-cysteine (64 g / l) dissolved in each concentration of disodium hydrogen arsenate and / or diarsenic trioxide at 0 to 20 ppm} 6. The working electrode 1, the reference electrode 2 and the counter electrode 3 are immersed in the sample aqueous solution, lead wires are taken out from each electrode, and a potentiostat (manufactured by ECO CHEMIE, trade name AUTOLAB)
PGSTAT 12) 4 was connected.

  The sample aqueous solution of each concentration was measured by the linear sweep voltammetry method on the measurement / analysis software GPES, and the obtained voltammogram is shown in FIG.

  In the figure, 7 is a voltammogram obtained from a sample aqueous solution containing 10 ppm trivalent arsenic ions and 10 ppm pentavalent arsenic ions, and 8 is obtained from a sample aqueous solution containing 4 ppm trivalent arsenic ions and 6 ppm pentavalent arsenic ions. 9 is a voltammogram obtained from a sample aqueous solution containing 2 ppm trivalent arsenic ions and 6 ppm pentavalent arsenic ions, 10 is a voltammogram obtained from a sample aqueous solution containing 6 ppm pentavalent arsenic ions, and 11 is a voltammogram. Voltammogram obtained from a sample aqueous solution containing 4 ppm pentavalent arsenic ions, 12 is a voltammogram obtained from a sample aqueous solution containing 2 ppm pentavalent arsenic ions, and 13 is a voltammogram of a control (sample aqueous solution not containing arsenic ions). It is.

  Both trivalent arsenic ions and pentavalent arsenic ions have a linearly proportional concentration and current sensitivity, and it was confirmed that not only qualitative measurement but also quantitative measurement is possible.

(Comparative Example 1)
In Example 1, when measurement was performed without adding L-cysteine, trivalent arsenic ions were detected quantitatively, but pentavalent arsenic ions could not be detected.

1 is a schematic diagram showing an electrochemical measurement device used in Example 1. FIG. 2 is a voltammogram obtained in Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Working electrode 2 Reference electrode 3 Counter electrode 4 Potentiostat 5 Glass cell container 6 Sample aqueous solution 7 Voltammogram obtained from sample aqueous solution containing 10 ppm trivalent arsenic ions and 10 ppm pentavalent arsenic ions 8 4 ppm trivalent arsenic ions and 6 ppm five Voltammogram 9 obtained from a sample aqueous solution containing divalent arsenic ions Voltammogram obtained from a sample aqueous solution containing 106 ppm pentavalent arsenic ions obtained from a sample aqueous solution containing 2 ppm trivalent arsenic ions and 6 ppm pentavalent arsenic ions Voltammogram 12 obtained from sample aqueous solution containing pentavalent arsenic ions Voltammogram obtained from sample aqueous solution containing 2 ppm pentavalent arsenic ions 13 Voltammogram of control (sample aqueous solution not containing arsenic ions)

Claims (10)

  The electrode is brought into contact with an aqueous solution in which arsenic ions and an electron mediator that binds to arsenic ions coexist or are combined, and the oxidation current value of arsenic ions flowing through the electrode in contact with the aqueous solution is measured. An electrochemical measurement method for arsenic ions.   An electron mediator that binds to arsenic ions is added to an aqueous solution containing arsenic ions, and the electrode is brought into contact with an aqueous solution that exists in a state where the arsenic ions and the electron mediator coexist or are combined. An electrochemical measurement method for arsenic ions, comprising measuring an oxidation current value of flowing arsenic ions.   An aqueous solution containing arsenic ions is allowed to act on a carrier that adsorbs arsenic ions, and then an eluent containing an electron mediator that binds to the arsenic ions is allowed to act on the carrier. An electrochemical measurement method for arsenic ions, comprising measuring an oxidation current value of arsenic ions flowing through an electrode in contact with a liquid.   The method for electrochemical measurement of arsenic ions according to any one of claims 1 to 3, wherein the electron mediator is an electron mediator that binds to pentavalent arsenic ions.   The method for electrochemical measurement of arsenic ions according to any one of claims 1 to 4, wherein the electron mediator is a compound having a thiol group.   6. The method for electrochemical measurement of arsenic ions according to claim 5, wherein the compound having a thiol group is cysteine.   Electrochemical measurement of arsenic ions, characterized in that an electrode containing an electron mediator that binds to arsenic ions is brought into contact with an aqueous solution containing arsenic ions and the oxidation current value of arsenic ions flowing through the electrode in contact with the aqueous solution is measured Method.   8. The method for electrochemical measurement of arsenic ions according to claim 7, wherein the electrode containing an electron mediator that binds to arsenic ions is a cysteine-containing gold electrode.   The electrochemical measurement method for arsenic ions according to any one of claims 1 to 8, wherein the electrochemical measurement method is a stripping voltammetry method.   10. The electrochemical measurement method for arsenic ions according to claim 9, wherein the stripping voltammetry method is a linear sweep voltammetry method or a square web voltammetry method.