Method for quantifying a chemical substance with substitutional stripping voltammetry and a sensor chip used therefor

A method for quantifying a chemical substance contained in a sample solution, comprising the following steps (a) to (e):

• a step (a) of preparing a sensor chip, wherein,
• the sensor chip comprises a substrate, a pair of working electrodes, a counter electrode, a stripping electrode, and a stripping gel,
• the pair of working electrodes is composed of a first working electrode and a second working electrode,
• the surface of the stripping electrode comprises silver,
• the stripping gel covers the stripping electrode,
• the stripping gel does not cover the pair of the working electrodes or the counter electrode,
• the stripping gel contains a standard electrolyte and an ionic liquid,
• the stripping gel contains no water,
• the ionic liquid is hydrophobic and nonvolatile,
• the ionic liquid is consisted of a cation and an anion,
• the standard electrolyte is consisted of the cation and a halide ion,
• a step (b) of supplying the sample solution to the surface of the sensor chip to cover the surface with the sample solution, wherein,
• the sample solution contains the chemical substance and an oxidation-reduction substance or contains the chemical substance modified with an oxidation-reduction substance,
• a step (c) of applying a potential to the first working electrode with potentiostat, and connecting the second working electrode to the stripping electrode to generate reactions represented by the following formulas (I) to (III) in the respective surface of the first working electrode, the second working electrode, and the stripping electrode, respectively,
• the first working electrode:
• (wherein, n represents an integer, and m represents a positive integer.)
• the second working electrode:
• (wherein, n represents an integer, and m represents a positive integer.)
• the stripping electrode:
• [Chem. 3]
• Ag+X⊖→AgX↓+e⊖ (III)
• (wherein, X represents iodine atom, bromine atom, or chlorine atom.)
• wherein, the silver halide is deposited on the surface of the stripping electrode,
• a step (d) of applying a potential to the stripping electrode in a condition where no potential is applied to either the first working electrode or the second working electrode to measure a current flowing through the stripping electrode,
• a step (e) of calculating the concentration of the oxidation-reduction substance (reductant) to quantify the chemical substance on the basis of the calculated concentration.