JP4869849B2 - Solution analysis method - Google Patents

Description

  The present invention relates to a solution analysis method capable of measuring (qualitatively and quantitatively) analyzing metal ions and the like by voltammetry comprising a working electrode, a counter electrode, and a reference electrode, for example, tap water, environmental water, soil It relates to a method capable of measuring and analyzing mercury, copper, arsenic, etc. contained in foods.

  Since tap water, environmental water, soil, food, and other solutions may contain various unintentional harmful substances (hazardous metals, etc.), problems have been raised, especially in tap water. Examination of revision of drinking water quality guidelines by the Health Organization (WHO) and revision of water supply law by the Ministry of Health, Labor and Welfare (the revised water law has been enforced since April 1, 2004 Effective from March 31, 2013).

  Examples of harmful substances include mercury (metal mercury, inorganic mercury compounds, organic mercury compounds (alkyl mercury (aliphatic mercury), aryl mercury (aliphatic mercury), etc.)), copper, lead, arsenic, etc. It has been pointed out that there is a possibility that it will affect the human body, etc. With this increase, various substances existing in nature (for example, environmental water and drinking water) are measured (qualitative and quantitative) and analyzed. The need for monitoring is pointed out.

  For example, as a method for analyzing heavy metals (measuring objects) contained in tap water, environmental water, soil, food, etc. (analyses), specific methods such as atomic absorption spectrometry, ICP emission spectrometry, ICP mass spectrometry, etc. A method of measuring (qualitative and quantitative) and analyzing a substance (measuring object) is known.

  For example, when the object to be measured is mercury, the atomic absorption method (sealed circulation method, open broadcast air) in which mercury present in the analyte is vaporized by reduction or heating, and then the vaporized mercury is measured and analyzed. Method) has been conventionally known. In the case of the atomic absorption method described above, if a volatile substance such as benzene or acetone is present in the analyte, the measurement is inhibited by the volatile substance. Limited (limited to analytes not containing volatile substances).

  However, in the above-mentioned official analysis method, the apparatus to be used is large and expensive, and technical skill and effort (such as a long time) are required for operation of the apparatus. It is not a thing.

  In recent years, paying attention to the fact that many of the harmful substances present in the solution have electrochemical activity, an attempt to analyze various harmful substances using electrochemical techniques, such as working electrodes (mercury electrodes, carbon-based electrodes) , A gold electrode, a copper electrode, etc.), an anodic stripping voltammetry method (hereinafter referred to as a voltammetry method) using a counter electrode, a reference electrode, and the like. This voltammetry method is simpler than the above-mentioned official analysis method (for example, downsizing and cost reduction of the apparatus used), and has high sensitivity and high accuracy (for example, determination of trace metal ion concentration). Therefore, it can be easily performed in a short time, and is also advantageous for analysis of an analyte (for example, seawater) containing a large amount of electrolyte.

  For example, when the measurement object is mercury, a method is known in which a gold rotating electrode is used as a working electrode and an amalgam is formed by the rotating electrode and analyzed (for example, Non-Patent Document 1). In addition, when the object to be measured is copper, a method is known in which a mercury electrode (an electrode using a mercury drop or the like) is used as a working electrode, and amalgam is formed at the mercury electrode for analysis. In addition, when a measuring object is lead, the method of using a copper electrode as a working electrode and reducing and concentrating lead on the surface of the copper electrode is known (for example, Patent Document 1).

However, even in the voltammetry method described above, for example, when a mercury electrode is used, the mercury electrode itself is a dangerous substance, and there are concerns about the handling method and environmental pollution. In addition, even when using electrodes other than mercury electrodes (carbon-based electrodes such as glassy carbon electrodes), for example, with the recent revision of drinking water quality guidelines and revisions to the Waterworks Law, etc., with higher sensitivity and higher accuracy. The emergence of analytical methods that can be analyzed is required.
Y. Bonfil, M.M. Brand, E .; Kirowa-Eisner, “Trace determination of ananodic stripping voltametry at attorting gold electrode” (Netherlands), Analytica Chimica Acta, Elvisumer, 2000, Vol. 65-76. JP 2004-294422 A

  As described above, it is a simplified method (for example, downsizing and cost reduction of the apparatus to be used) compared to the conventional analysis method, and the analysis is more sensitive and accurate (for example, trace metal). It has been desired to develop an analysis method that can easily measure ions) in a short period of time, and that does not require handling of hazardous materials or environmental pollution.

  The present invention is a voltammetry method using a gold electrode as a working electrode in order to solve the above-mentioned problems, and the working electrode is activated under a predetermined condition before performing an analysis operation. The electric double layer capacitance decreases, the background current (hereinafter referred to as BG current) of the working electrode is attenuated, and the signal / background ratio (hereinafter referred to as S / B ratio) is increased. The analysis object can analyze at least one of mercury, copper, and arsenic with higher sensitivity and higher accuracy.

Specifically, the invention described in claim 1 includes a working electrode, a counter electrode (for example, a platinum electrode in the embodiments described later), and a reference electrode (for example, an Ag / AgCl reference electrode in the embodiments described later). After being placed in an analysis target (for example, tap water, environmental water, soil extract, food extract, etc.), the potential of the working electrode is held at a potential that can be reduced by the measurement target in the analysis target. While sweeping the potential of the held working electrode and the potential of the held working electrode in a positive direction in which the measurement target in the analysis target can be oxidized (for example, in the embodiment described later, sweeping with a differential pulse), A potential sweep step for detecting a current change with respect to a potential change at the working electrode, wherein the working electrode uses a gold electrode and contains chloride ions before the analyzing operation. Solution (solution not subject to analysis) Alternatively, a pre-analysis activation potential is applied in an analyte to be analyzed in which chloride ions coexist, and the pre-analysis activation treatment is performed. There line analysis before activation potential of said, characterized in that the gold electrode under chloride ions coexist is potential to cause oxidation dissolution reaction.

The invention according to claim 2 is characterized in that, in the invention according to claim 1 , the pre-analysis activation potential excludes a potential at which bubbles of oxygen and chlorine are generated from the potential causing the oxidation elution reaction. And

The invention according to claim 3 is the invention according to claim 2 , wherein the pre-analysis activation potential is within a range excluding the potential at which an oxide film is formed on the gold electrode surface in the presence of chloride ions. Features.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, when the analysis operation is repeatedly performed, an inter-analysis activation potential is applied to the working electrode between the analysis operations to perform inter-analysis activity It is characterized by performing the conversion process.

The invention according to claim 5 is the invention according to claim 4 , wherein the inter-analysis activation potential includes oxygen and chlorine bubbles among the potential at which the gold electrode undergoes an oxidation elution reaction in the presence of chloride ions. It is characterized in that the generated potential is excluded.

The invention according to claim 6 is the invention according to claim 5 , wherein the inter-analysis activation potential is a potential at which an oxide film is formed on the gold electrode surface in the presence of chloride ions. .

A seventh aspect of the invention is characterized in that, in the first to sixth aspects of the invention, the measurement object includes at least one of mercury, copper, and arsenic.

In the inventions according to claims 1 to 7 , since the working electrode is a gold electrode and pre-analysis activation treatment is performed in the presence of chloride ions (for example, in an analysis target containing chloride ions), the potential is The BG current having current characteristics obtained by the analysis operation in the holding process and the potential sweep process is stabilized. In addition, the pre-analysis activation treatment not only causes the oxidative elution reaction of the working electrode, but also attenuates the BG current and increases the S / B ratio.

  Furthermore, when the oxidation elution reaction occurs, the electrode surface is roughened, and the electrodeposition efficiency is improved as the working electrode surface area is increased. Furthermore, in the inter-analysis activation treatment, when the potential at which an oxide film is formed on the gold electrode surface in the presence of chloride ions is removed, the electrodeposition efficiency of the electrodeposition substance at the working electrode is further improved. In addition, by removing the potential at which bubbles such as oxygen and chlorine are generated in the pre-analysis activation potential and the inter-analysis activation potential, it is possible to avoid the influence of the analysis due to the generation of bubbles.

According to the first to seventh aspects of the present invention, there is no need for a large-sized, expensive, and complicated operation device (simplification) as in the conventional analysis method, and the handling of hazardous materials and environmental pollution are taken into consideration. It is a method that does not need to be performed, the working electrode is activated, and high-sensitivity and high-precision analysis can be easily performed in a short time with respect to the analysis target. For example, when the working electrode 2 has deteriorated, it is regenerated by electrolytic polishing before the analysis is started.

In addition, according to the invention described in claims 3 to 6 , even if the analysis operation is repeated, the electrode is regenerated, maintaining high sensitivity and high accuracy analysis, and reproducibility of analysis is obtained.

  Hereinafter, the solution analysis method in this Embodiment is demonstrated based on drawing etc. FIG.

  This embodiment uses a working electrode, a counter electrode, and a reference electrode, and uses a voltammetry method to analyze an analysis target such as tap water (for example, a solution such as tap water containing a measurement target such as mercury, copper, and arsenic). The gold electrode immersed in the analyte in which chloride ions coexist is activated under a predetermined condition using a gold electrode as the working electrode (pre-analysis activation treatment and analysis described later). Measurement object (at least one of mercury, copper, and arsenic) is measured and analyzed. In the activation process (especially, the pre-analysis activation process described later), even a solution other than the analysis target may be a solution containing chloride ions.

  In the activation treatment, a potential having a predetermined magnitude is applied to a working electrode (a constant potential is applied) in a state where chloride ions as anion species coexist in the analyte. The electric double layer capacity of the electrode is reduced, and the BG current is attenuated.

In Non-Patent Document 1, after polishing the working electrode (a rotating electrode made of a gold electrode), a relatively large constant current (150 mA / cm ² ; very large current in the field of voltammetry) with respect to the working electrode. Although it can be read that the baseline of the peak current that can be detected is made flat (stabilization of the BG current), there is no disclosure or suggestion of reducing the BG current. Further, it is described that bubbles (oxygen) are generated on the surface of the working electrode because a very large constant current is applied, and the form of the working electrode is limited to the rotating electrode. Furthermore, it is impossible to read the potential applied to the working electrode at the time of energization (potentially applied potential) simply by disclosing the contents of conducting a constant current (Non-Patent Document 1). Item 2.4.1 “Activating the gold electrode”, FIG. 1 etc.).

In Patent Document 1, copper is a base metal (a metal that is easily oxidized), and easily causes an oxidation elution reaction (Cu → Cu ²⁺ + e ⁻ ) without being limited to the type of electrolyte (depending on the type of electrolyte). In order to clean the surface of the working electrode (copper electrode) simply, the potential of the working electrode is set to a negative potential, focusing on the fact that it is easily oxidized and eluted at a potential around ± 0 V (vs. Ag / AgCl). Sweep from the side to a positive potential (maintained at a positive potential slightly exceeding ± 0 V (vs. Ag / AgCl) (approximately 0 to 150 mV)), and the surface of the working electrode is oxidized and eluted at the molecular level for regeneration treatment However, there is no disclosure or suggestion of reducing the BG current (claim 14 of Patent Document 1).

  On the other hand, in this embodiment, a gold electrode that is a noble metal (a metal that is difficult to oxidize) is used as a working electrode, and analysis is performed in a state where chloride ions coexist in an analysis target. A relatively high positive potential at a working electrode immersed in a coexisting analyte (or a solution containing chloride ions) (potential at which the working electrode undergoes an oxidative elution reaction; for example, Example 1 described later) In this case, the activation process is performed by applying a potential in the positive direction from about +1000 mV (preferably a potential in the positive direction from about +1400 mV).

  That is, in this embodiment, the gold electrode oxidizes and elutes at a predetermined potential only in the presence of chloride ions and becomes electrochemically active, whereby the BG current of the gold electrode is only stabilized. In other words, the present inventors have found that the electric double layer capacity is reduced and the BG current itself is reduced. Therefore, the electrode activation process in the present embodiment depends on the applied potential, and is different from that in which a constant current is applied as in Non-Patent Document 1.

  Further, when the applied potential of the activation process is, for example, a level exceeding +2 V (for example, 5 V), it is considered that bubbles may be generated on the surface of the working electrode. However, a level of +1 V to +2 V (for example, an example described later) ), There is almost no need to consider the generation of bubbles (especially, in the case of a measurement target (mercury or the like) that hardly interferes with the analysis due to the generation of bubbles), and the shape of the electrode may be limited. No. The applied potential is preferably set to a potential at which bubbles do not occur as described above (for example, +2 V or less). However, even if the applied potential is higher than +2 V, for example, mass transfer promoting means ( By appropriately setting (for example, increasing the rotation speed of the stirrer) by appropriately setting a stirrer 7, a stirrer 7a, etc., which will be described later, the influence of the bubbles (for example, In the embodiments described later, there is a possibility that the activation process may not be performed).

  In particular, in the pre-analysis activation treatment, the solution (solution used for the analysis activation treatment) may be clearly colored or a large amount of chlorine may be generated due to the oxidation elution reaction of the gold electrode. In such a case, it is preferable to perform the pre-analysis activation process in another solution (in a solution containing chloride ions) without performing the pre-analysis activation process in the analysis target.

[Example of equipment applied to analysis method]
FIG. 1 is a schematic diagram showing an example of an apparatus applied to the analysis method in the present embodiment. In FIG. 1, reference numeral 1 denotes a measurement container (cell). The measurement container 1 contains an object to be analyzed (for example, tap water) 1a and is sealed by a sealing member 1b. . Reference numeral 2 is a working electrode made of a gold electrode (for example, a substantially cylindrical or substantially flat electrode), reference numeral 3 is a counter electrode (for example, a coiled electrode made of platinum or carbon), and reference numeral 4 is a reference electrode (a reference electrode). For example, an Ag / AgCl electrode (saturated potassium chloride) or a saturated calomel electrode), and the working electrode 2, the counter electrode 3, and the reference electrode 4 are separated from each other by a certain distance, It is provided so as to be immersed in the object 1a to be analyzed in the measurement container 1.

  Reference numeral 5 denotes a potentiostat, and the working electrode 2, the counter electrode 3, and the reference electrode 4 are connected to the potentiostat 5 through, for example, wirings 2a, 3a, 4a and the like. Further, the potentiostat 5 includes a computer (for example, a personal computer) 6 capable of performing calculations related to measurement data obtained through the potentiostat 5 and the like, and a recorder, a potential sweeper as necessary. Etc. are connected. Reference numeral 7 denotes a stirrer, and the stirrer 7 a located at the bottom of the measurement container 1 is operated by the stirrer 7 to stir the object 1 a to be analyzed in the measurement container 1.

  Next, an outline of an analysis method using the apparatus shown in FIG. 1 will be described. First, in order to promote the movement of the measurement object to the surface of the working electrode 2, the substance movement in the analysis object 1a is performed by stirring (turbulent flow) the analysis object 1a via the stirrer 7 and the stirring bar 7a. While promoting the mass transfer of the electrochemically active substance, that is, the electrodeposition efficiency (reduction deposition efficiency) or amalgam formation efficiency of the electrodeposition substance described later), the potential of the working electrode 2 (by the reference electrode 4) by the potentiostat 5 The regulated potential is set to a desired potential (potential at which the measurement target can be reduced (electrodeposition or amalgam formation)) and held for a predetermined time, and the measurement target in the target 1a to be analyzed is on the surface of the working electrode 2 Reduce to form electrodeposition or amalgam. Thereafter, the potentiostat 5 causes the potential held by the working electrode 2 to move in the positive direction (the positive potential side on which the measurement target can be oxidized) under a predetermined condition (for example, a differential pulse in the embodiments described later). By sweeping, the electrodeposition material or amalgam is eluted (anode stripping) into the analyte 1a by an oxidation reaction.

  Since the electrodeposition substance and the amalgam are eluted at a predetermined potential, respectively, when the potential of the working electrode 2 is swept (the electrodeposition substance and the amalgam are eluted in the analyte 1a), the working electrode 2 detects a current change (change in oxidation current; change in current flowing between the working electrode 2 and the counter electrode 3) with respect to the potential change of 2. Then, by comparing the electric quantity (coulomb quantity) or peak current value obtained by integrating the change in current with a calibration curve, the measurement object is measured (quantitative, qualitative), and the analysis object 1a is analyzed (mercury , Analysis by measurement of copper concentration, etc.).

  Next, using various samples S1 to S12b (corresponding to the object 1a to be analyzed), shown in a schematic explanatory diagram of FIG. 1 (the same reference numerals are used for the same components as in FIG. 1 and the detailed description is omitted). Examples of the supporting electrolyte (various anion species and concentration) suitable for such analysis, pH of the buffer solution, potential of the working electrode 2 (potential of the working electrode 2 in the potential holding step described later), etc. 6 to verify. Then, as in Examples 1 to 15, after the working electrode 2 is activated, analysis of various samples S13 to S23 (corresponding to the analysis target 1a) containing copper ions, mercury ions, arsenic ions, and the like is performed. Went.

  In the analysis apparatus shown in FIG. 1, the working electrode 2, the counter electrode 3 and the reference electrode 4 are electrodes (OD) manufactured by Hokuto Denko Co., Ltd., each of which is formed by embedding a gold electrode in a contracted Teflon (registered trademark) tube. 6 mm, ID; 3 mm), a Φ0.5 mm coiled platinum wire, and an Ag / AgCl electrode (HX-R6 manufactured by Hokuto Denko). The measuring vessel 1 was a 50 mL glass beaker, and the potentiostat 5 was HOE-100 manufactured by Hokuto Denko. The working electrode 2 was used after the surface was polished with sandpaper (# 1200).

(Verification example 1)
In this verification example 1, a solution of potassium chloride (KCl), potassium sulfate (K ₂ SO ₄ ), and potassium nitrate (KNO ₃ ) (each 0.1 M solution) was used as samples S1 to S3, and the samples S1 to S3 were used. The click voltammogram was verified. First, it sealed with the sealing member 1b so that the working electrode 2, the counter electrode 3, and the reference electrode 4 might be immersed.

  Thereafter, for the samples S1 to S3, the potential of the working electrode 2 with respect to the reference electrode 4 is swept within a range of 0 V to +1.6 V, and a current change with respect to the potential change of the working electrode 2 is detected, thereby obtaining a diagram. A cyclic voltammogram as shown in FIGS. 2A to 2C was obtained.

  From the results shown in FIGS. 2B and 2C, it can be read that no oxidation elution reaction occurs in the samples S2 and S3 using the potassium sulfate solution and the potassium nitrate solution. On the other hand, from the results shown in FIG. 2A, in the case of sample S1 using a potassium chloride solution, the oxidation elution reaction occurred between about +1 V and a predetermined positive potential (from about +0.9 V to about +1.6 V in FIG. 2A). I can read what is happening. The reason why the oxidation elution reaction occurs is considered to be due to a complex formation reaction between gold and chloride ions as shown in the following formula.

Au + 4Cl ⁻ → AuCl ₄ + 3e ⁻ [+1000 mV (vs. NHE)] (1)
Au + 2Cl ⁻ → AuCl ₂ + e ⁻ [+1100 mV (vs. NHE)] (2).

Next, the same potassium chloride (KCl) solution (1M solution) as that of the sample S1 is used as the sample S1a, and the potential of the working electrode 2 with respect to the reference electrode 4 is within the range of 0 mV to +2000 mV by the same operation as the sample S1. 3 detected a current change with respect to the sweep (sweep speed 100 mV / s) and the potential change of the working electrode 2, and a cyclic voltammogram as shown in FIG. 3 was obtained. From the results shown in FIG. 3, it can be seen that in the case of the sample S1a, the oxidation elution reaction takes place from around +900 mV to a predetermined positive potential (in the vicinity of +900 mV to +2000 mV in FIG. 3).

  When the oxidation elution reaction occurs as described above, the working electrode 2 is consumed according to the magnitude of the oxidation elution reaction, but the surface roughness of the surface of the working electrode 2 increases (the surface area of the working electrode 2 increases). ), It is considered that the electrodeposition efficiency (reduction deposition efficiency) of the electrodeposition material on the surface of the working electrode 2 increases according to the surface roughness (particularly, copper, arsenic, etc.).

  Note that the reason why the difference is observed in the results of FIGS. 2A and 3 is considered to be due to the difference in the chloride ion concentration, pH, etc. of the samples S1 and S1a.

  Further, as shown in FIGS. 2A and 3, a potential region in which the oxidation elution reaction is extremely small at a potential in the positive direction relative to the potential at which the peak current is generated (for example, in the vicinity of +1.35 V to about 1.5 V in FIG. In FIG. 3, around +1400 mV to around +1700 mV) is observed, but it is considered that an oxide film is formed on the surface of the working electrode 2 in this potential region. In this case, although the electrodeposition efficiency of the electrodeposition material is hardly improved, the consumption of the working electrode 2 can be suppressed.

  Further, in the potential in the positive direction than the potential region in which the oxidation elution reaction is extremely small, a potential region in which the oxidation elution reaction is relatively small (for example, around +1.5 V to 1.6 V in FIG. 2A, around +1700 mV in FIG. 3). In the potential region, it is considered that oxygen and chlorine are generated on the surface of the working electrode 2. Here, in the case of a measurement object whose analysis is hindered by oxygen, chlorine, or the like, it is preferable to avoid the influence of the bubbles (for example, in the examples described below, the possibility of not being activated), It is possible to perform a sufficiently good analysis on the measurement target (such as mercury).

  Therefore, in the analysis by the apparatus as shown in FIG. 1, when chloride ions coexist in the object 1a to be analyzed, the potential at which the oxidative elution reaction of the working electrode occurs with respect to the working electrode 2 made of a gold electrode ( For example, in this verification example 1, by applying a potential of about +0.9 V to +1 V or more), an oxidation elution reaction is caused in the working electrode 2, so that the working electrode 2 deteriorates due to repeated analysis operations (for example, It has been found that the working electrode 2 can be regenerated (maintaining the reproducibility of the analysis) even if the surface shape changes, dirt, etc. (for example, organic substances such as proteins that can adhere to the electrode surface).

(Verification example 2)
In this verification example 2, each analysis was verified using the analyte to be analyzed in which various anion species coexist and containing copper ions. First, a sample S4 is obtained by blending 0.1 mM potassium chloride solution with 10 mM (concentration required to exhibit a buffering effect) acetate buffer solution (pH 4.5) and 0 to 200 nM copper ions. It was. Next, it sealed with the sealing member 1b so that the working electrode 2, the counter electrode 3, and the reference electrode 4 might be immersed in the said sample S4.

  Thereafter, the potential of the working electrode 2 with respect to the reference electrode 4 is maintained at −50 mV for 180 seconds while maintaining a mass transfer accelerating atmosphere via the stirrer 7 and the stirring bar 7a. 2 Electrodeposited on the surface (potential holding step).

  Then, after the stirrer 7 and the stirring bar 7a are stopped, the potential of the working electrode 2 with respect to the reference electrode 4 is changed from -50 mV in the linear sweep mode (LSV condition 25 mV / s) in the positive direction (the electrodeposition material is oxidized). By sweeping to the positive potential side), the electrodeposition material on the surface of the working electrode 2 is eluted in the sample S1 (anode stripping), and a current change with respect to the potential change of the working electrode 2 is detected (potential sweep). The detection results are shown in the current change characteristic diagrams with respect to potential changes in FIGS. 4A to 5E for each copper ion concentration.

  Further, samples S5 and S6 are obtained using a potassium sulfate solution or a potassium nitrate solution instead of the potassium chloride solution of the sample S4, and the potential holding step and the potential sweep step are performed by the same analytical operation as the sample S4. The current change characteristics with respect to the potential change were obtained, and the respective results were shown in the current change characteristics diagrams of FIGS. 6A to 8 and FIGS. 9A to 11 for each copper ion concentration.

  First, as shown in FIGS. 6A to 7C and FIGS. 9A to 10E, in the case of samples S5 and S6, a sufficient peak current can be read from the current characteristics at each copper ion concentration, as shown in FIGS. 8 and 11, respectively. In addition, although the characteristic line of the electric quantity of each peak current with respect to the copper ion concentration has linearity, each intercept showed a negative value. For this reason, when a potassium sulfate solution or a potassium nitrate solution is used, it is considered that the quantitative and reproducibility is inferior because the reduction and concentration efficiency of copper ions with respect to the electrode is low.

  On the other hand, as shown in FIGS. 4A to 5E, in the case of the sample S4, it can be read that although the increase in peak intensity corresponding to the concentration is observed in each current characteristic, the stability of the BG current is lacking.

  Therefore, the sample S4 using the potassium chloride solution is subjected to the potential holding step as described above, and then the differential pulse mode (pulse condition: pulse period 100 ms, pulse interval 50 ms, pulse height 50 mV) in the potential sweep step. The current change with respect to the potential change of the working electrode 2 was detected by sweeping in the positive direction from -500 mV, and the detection results are shown in the current change characteristic diagrams of FIGS. 12A to 14B for each copper ion concentration.

  As shown in FIGS. 12A to 14B, when the potential sweep process is performed in the differential pulse mode in the analysis of the sample S4, the BG current of each current characteristic is sufficiently stable compared to the case where the potential sweep process is performed in the linear sweep mode. I can read that. Moreover, as shown in FIG. 15, it can be read that the characteristic line of each peak current value with respect to the copper ion concentration has linearity. The intercept of the characteristic line in FIG. 15 showed a positive value. The reason for this is due to contamination in the sample S4, which is considered to be a level that does not hinder the analysis, and it can be read that the electrodeposition efficiency is sufficient. .

  For samples S5 and S6 using a potassium nitrate solution and a potassium sulfate solution, the potential sweep step is performed in the differential pulse mode, and a characteristic curve (calibration curve) is obtained from the result of current change (each peak current value) with respect to potential change of the working electrode 2. The characteristic line intercepts showed negative values (not shown). From this result, it is considered that the conditions (linear sweep mode, differential pulse mode) in the potential sweep process are independent of the electrodeposition efficiency.

  Therefore, in the analysis by the apparatus as shown in FIG. 1, if the anion species coexisting in the analyte 1a is chloride ions (that is, chloride ions coexist in the analyte at the time of analysis). When the differential pulse mode is selected as the condition for the potential sweep process, the BG current is more stable and each peak current value characteristic line with respect to the copper ion concentration is reliable. It was found that it can be applied as a high calibration curve. In addition, it is thought that even if it is a to-be-analyzed object containing mercury ion instead of the copper ion, it has a tendency similar to that in this verification example 2.

(Verification Example 3)
In this verification example 3, each analysis result was verified using an analyte to be analyzed in which various concentrations of chloride ions including copper ions or mercury ions coexist.

  First, 20 mM to 150 mM potassium chloride solution was used as a supporting electrolyte, and 10 mM acetate buffer solution (pH 4.5) and 200 nM copper ions were blended to obtain sample S7. Then, for the concentration of the potassium chloride solution, the sample S7 is analyzed by the potential holding step and the potential sweep step (differential pulse mode (pulse condition: pulse period 100 ms, pulse interval 50 ms, pulse height 50 mV) similar to those in the verification example 2. The operation was performed to detect current change characteristics with respect to potential changes, and the respective detection results are shown in the peak current value characteristic chart with respect to the potassium chloride solution concentration in FIG.

  A sample S8 was obtained by blending 20 mM to 100 mM potassium chloride solution as a supporting electrolyte and 10 mM acetate buffer solution (pH 4.5) and 200 nM mercury ions. Then, with respect to the sample S8, for each concentration of the potassium chloride solution, a potential holding step (the potential of the working electrode 2 is held at +300 mV), a potential sweep step (sweep from +300 mV in the linear sweep mode (LSV condition 25 mV / L). The current change characteristics with respect to the potential change were detected by performing the analysis operation according to s)), and the respective detection results are shown in the peak current value characteristic chart with respect to the potassium chloride solution concentration in FIG.

  In the characteristic curve shown in FIG. 16, a sufficiently large peak current is detected in the potassium chloride solution concentration range of 20 mM to 150 mM, and as the potassium chloride solution concentration increases, the magnitude of the peak current increases. It can be seen that it has a tendency to rise.

  In the characteristic curve shown in FIG. 17, it can be seen that a relatively large peak current is detected in the potassium chloride solution concentration range of 20 mM to 30 mM. Further, it can be read that each peak current is sufficiently large although the magnitude of the peak current tends to gradually decrease as the potassium chloride concentration becomes higher than 30 mM.

  Therefore, in the analysis as shown in FIG. 1, if the chloride ion concentration in the analyte 1a is within the range of 20 mM to 150 mM (preferably, for example, 150 mM within this range), the analyte in the analyte 1a It was found that copper ions can be measured sufficiently. It is also found that mercury ions in the analyte 1a can be sufficiently measured if the chloride ion concentration in the analyte 1a is within a range of 20 mM to 100 mM (preferably, for example, 20 mM to 30 mM within this range). did.

(Verification Example 4)
In this verification example 4, the analysis results were verified using buffer solutions with various pH values and analytes containing copper ions or mercury ions. First, a 150 mM potassium chloride solution was used as a supporting electrolyte, and a 10 mM acetate buffer solution adjusted in the range of pH 3.5 to pH 5.5 and 200 nM copper ions were blended to obtain sample S9. Then, for each sample S9, for each pH (different pH) of the buffer solution used, the current change characteristics with respect to the potential change are obtained by performing the analysis operation by the potential holding step and the potential sweep step similar to those of the sample S7 in the verification example 3, The peak current values of these current characteristics are shown in FIG. 18 as characteristics with respect to the pH of the buffer solution.

  A sample S10 was obtained by using a 25 mM potassium chloride solution as a supporting electrolyte and a 10 mM acetate buffer solution adjusted to a pH of 3.5 to 4.5 and 200 nM mercury ions. Then, for each sample S10, for each pH of the buffer solution used (different pH), the analysis operation by the potential holding step and the potential sweep step similar to those of the sample S8 in the verification example 3 is performed to obtain the current change characteristics with respect to the potential change, The peak current values of these current characteristics are shown in FIG. 19 as characteristics with respect to the pH of the buffer solution.

  In the characteristic curve of FIG. 18, it can be seen that each peak current is sufficiently large, and the peak current has a tendency to gradually increase as the pH of the buffer solution increases. Moreover, it can be read that each peak current is substantially constant and stable within the range of pH 4 to pH 5.

  In the characteristic curve of FIG. 19, it can be read that each peak current is sufficiently large although the magnitude of the peak current tends to gradually decrease as the pH of the buffer solution increases.

  Therefore, in the analysis as shown in FIG. 1, the buffer solution is pH 3.5 to pH 4.5 (preferably within this range, for example, pH 4.5 in the case of copper ions and pH 3.5 in the case of mercury ions). It was proved that copper ions or mercury ions in the analyte 1a can be sufficiently measured by using.

(Verification Example 5)
In this verification example 5, in consideration of the fact that the oxidation potentials of copper ions and lead ions are substantially close to each other, the potential of the working electrode 2 in the potential holding step is set to various values, and the respective analysis results are obtained. Verified. First, a sample S11a was obtained by blending a 150 mM potassium chloride solution as a supporting electrolyte and a 10 mM acetate buffer solution (pH 4.5) and 200 nM copper ions. In addition, using the same supporting electrolyte and acetate buffer solution as sample S11a, 200 nM of lead ion was used instead of copper ion to obtain sample S11b.

  Thereafter, the sample S11a and S11b were subjected to the analysis operation by the potential holding process and the potential sweep process similar to the sample S7 of the verification example 3, and current change characteristics with respect to the potential change were respectively obtained. The potential of the working electrode 2 in the potential holding step of this verification example 5 was set in the range of +250 mV to −300 mV in the case of the sample S11a and in the range of −50 mV to −300 mV in the case of the sample S11b. Then, the peak current value of each current characteristic was obtained for each set potential of the working electrode 2 (potential of different working electrode 2), and these peak current values were shown in FIG. 20 as characteristics with respect to the potential of the working electrode 2.

  As shown in FIG. 20, in the characteristic curve 11a (in the case of the sample S11a), the peak current value increases (below +200 mV) as the potential of the working electrode 2 in the potential holding step is changed from +200 mV to the negative direction side. It can be seen that electrodeposition starts and becomes substantially constant at about ± 0 V or less. On the other hand, in the characteristic curve 11b (in the case of the sample S11b), the peak current value increases as the potential of the working electrode 2 in the potential holding step is changed from −100 mV to the negative direction (the electrodeposition starts from less than −100 mV). It can be read.

  Therefore, in the analysis as shown in FIG. 1, when the analyte 1a contains copper ions and lead ions and the potential of the working electrode 2 in the potential holding step is less than −100 mV, lead ions are reduced in addition to copper ions. Due to the concentration, an alloy of copper and lead may be formed during the concentration. When measuring only copper ions in the analyte 1a, the potential of the working electrode 2 in the potential holding step is within a range of ± 0 mV to −100 mV (preferably within this range, for example, −50 mV). It turned out to be good to set to.

(Verification Example 6)
In this verification example 6, in consideration of the fact that the oxidation potentials of mercury ions and copper ions are substantially close to each other, the potential of the working electrode 2 in the potential holding step is set to various values, and the respective analysis results are obtained. Verified. First, a sample S12a was obtained by blending a 10 mM acetate buffer solution (pH 3.5) and 200 nM mercury ions with a 25 mM potassium chloride solution as a supporting electrolyte. Further, using the same supporting electrolyte and acetate buffer solution as in sample S12a, 200 nM of copper ion was used instead of mercury ion to obtain sample S12b.

  Thereafter, for the samples S12a and S12b, the analysis operation by the potential holding step and the potential sweep step similar to those of the sample S8 in the verification example 3 was performed, and current change characteristics with respect to the potential change were respectively obtained. The potential of the working electrode 2 in the potential holding step of this verification example 6 was set in the range of +600 mV to −100 mV in the case of the sample S12a and in the range of +400 mV to −50 mV in the case of the sample S12b. And the peak current value of each current characteristic was calculated | required for every setting electric potential (potential of different working electrode 2) of the working electrode 2, and these each peak current value was shown in FIG. 21 as the characteristic with respect to the electric potential of the working electrode 2. FIG.

  As shown in FIG. 21, in the characteristic curve 12a (in the case of the sample S12a), the peak current value increases as the potential of the working electrode 2 in the potential holding process becomes negative from +450 mV (electrodeposition from less than +450 mV). ) Can be read. On the other hand, in the characteristic curve 12b (in the case of the sample S12b), it can be seen that the peak current value increases (electrodeposition from less than +300 mV) as the potential of the working electrode 2 in the potential holding step becomes negative from +300 mV. .

  Therefore, in the analysis as shown in FIG. 1, when the analyte 1a contains mercury ions and copper ions, an amalgam of mercury ions and copper ions is formed when the potential of the working electrode 2 in the potential holding step is less than +300 mV. There is a possibility that. When measuring only mercury ions in the analyte 1a, the potential of the working electrode 2 in the potential holding step is set within a range of +450 mV to +300 mV (preferably, for example, +300 mV within this range). It turned out to be good.

Example 1
In the first embodiment, before analysis (before measurement), various positive potentials are applied to the working electrode 2 (applying constant potential) in the analyte 1a containing copper ions (in the presence of chloride ions) 1a. Thus, the working electrode 2 was activated (hereinafter referred to as pre-analysis activation treatment), and each analysis was performed. First, 150 mM potassium chloride solution was used as a supporting electrolyte, and 10 mM acetate buffer solution (pH 4.5) and 200 nM copper ions were blended to obtain sample S13.

  Next, after sealing with the sealing member 1b so that the working electrode 2, the counter electrode 3, and the reference electrode 4 are immersed in the sample S13, the potential of the working electrode 2 with respect to the reference electrode 4 is +700 mV to +1600 mV. For 30 seconds (holding constant potential) (pre-analysis activation treatment of working electrode immersed in sample S13).

  Thereafter, the sample S13 is subjected to the analysis operation by the potential holding step (the potential of the working electrode 2 is held at −50 mV) and the potential sweep step in the same manner as the sample S7 in the verification example 3, and the current change characteristics with respect to the potential change are respectively obtained. The results are shown in FIGS. 22A to 23B for each potential of the pre-analysis activation treatment (hereinafter referred to as pre-analysis activation potential). Note that the potentials (+700 mV to +1600 mV) in each of FIGS. 22A to 23B indicate the pre-analysis activation potential.

  As shown in the characteristic curves of FIGS. 22A to 23B, each peak current is detected with a sufficient magnitude, and as the pre-analysis activation potential is shifted from about +1000 mV to the positive direction, the BG current is attenuated and each peak is detected. It can be seen that the current is clear and sharp. It can be seen that this tendency (activation reaction) becomes stronger as the pre-analysis activation potential increases from about +1600 mV to the positive direction.

  This may be because the electrical double layer capacity is reduced and the S / B ratio is increased by the pre-analysis activation treatment. In addition, since chloride ions coexist in the sample S13, when the pre-analysis activation potential is about +1000 mV or more, the working electrode 2 is regenerated (for example, the working electrode 2 as shown in Verification Example 1). It can be seen that the material can be regenerated by electropolishing before the start of the analysis when it has deteriorated. Furthermore, from the results of Verification Example 1 and Example 1 (and Example 7 to be described later), the oxidation elution reaction tends to be suppressed as the pre-analysis activation potential is shifted from about +1400 mV to the positive direction side. However, it can be read that the activation reaction is higher.

  Even when the pre-analysis activation potential is much higher than +1600 mV (for example, higher than +2 V level), the S / B ratio can be increased to attenuate the BG current and make each peak current clear and sharp. Although there is a possibility, bubbles may be generated on the surface of the working electrode 2. When the bubbles are attached to the surface of the working electrode, there is a possibility that the pre-analysis activation process is not performed depending on the attached part.

  Therefore, in the analysis as shown in FIG. 1, before the potential holding step, for example, a pre-analysis activation potential of +1000 mV or more with respect to the working electrode 2 in the presence of chloride ions (preferably from +1400 mV in Example 1). Applying about +2000 mV (potential immediately before bubbles are generated from the working electrode)), pre-analysis activation treatment not only stabilizes the BG current but also attenuates it, and a clearer peak current is detected. Thus, it was found that analysis with higher sensitivity and higher accuracy is possible. When the pre-analysis activation potential in the pre-analysis activation process is about +1000 mV or more (preferably about +1400 mV to +2000 mV in the first embodiment), the working electrode 2 is used during the pre-analysis activation process. Regeneration processing (regeneration processing before the start of analysis) was carried out, and it was found that the activated state was maintained and the analysis was reproducible.

(Example 2)
In the present Example 2, the application time of the pre-analysis activation potential (hereinafter referred to as pre-analysis activation time) is set to various times in the analyte 1a containing copper ions, and the analysis of the sample S13 is performed. Carried out. First, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S13 was performed by setting the pre-analysis activation potential + 1600 mV and the pre-analysis activation time of 10 seconds to 70 seconds. Then, the sample S13 is subjected to the analysis operation by the potential holding step and the potential sweep step similar to those of the first embodiment to obtain the current change characteristics with respect to the potential change, and the results of the respective current change characteristics are obtained for each activation time before the analysis. This is shown in FIG.

  As shown in FIG. 24, the peak currents of the characteristic curves 23a to 23h are detected with a sufficient magnitude, and as the pre-analysis activation time increases, the BG current decays and the peak currents become clear. I can read that Further, it can be read that the BG current is sufficiently attenuated in the characteristic curves 23e to 23h whose activation time before analysis is 40 seconds or more, and the degree of attenuation is substantially constant. Even if the pre-analysis activation time is set to more than 70 seconds, the BG current may be substantially constant or further attenuated, but the analysis time becomes long.

  Therefore, in the analysis as shown in FIG. 1, the BG current is sufficiently attenuated by setting the pre-analysis activation time to 40 seconds or more (preferably, for example, 50 seconds in the second embodiment), and the peak current is sufficiently clear. It was found that analysis with higher sensitivity and higher accuracy is possible.

(Example 3)
In Example 3, after performing the pre-analysis activation process as described above on the analyte 1a containing copper ions, the analysis operation including the potential holding step and the potential sweep step was repeatedly performed, and the analysis was performed. . First, a sample S14 was obtained by blending a 150 mM potassium chloride solution as a supporting electrolyte and a 10 mM acetate buffer solution (pH 4.5) and 150 nM copper ions.

  Thereafter, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S14 was performed by setting the pre-analysis activation potential + 1600 mV and the pre-analysis activation time of 50 seconds. Then, for the sample S14, the analysis operation by the potential holding process and the potential sweep process similar to those in the first embodiment is repeated 40 times to obtain the current change characteristics with respect to the respective potential changes, and the respective peak currents of the respective current change characteristics. The values are shown in FIG. 25 for each analysis operation.

  In Example 3, a predetermined potential (potential with respect to the reference electrode 4) is applied to the working electrode 2 immersed in the sample S14 for a short time for each analysis operation (potential holding step, potential sweeping step). Then, activation processing of the working electrode 2 (hereinafter, activation processing for each analysis operation is referred to as inter-analysis activation processing). The potential applied in this inter-analysis activation treatment (hereinafter referred to as inter-analysis activation potential) was set to +1600 mV, and the application time (hereinafter referred to as inter-analysis activation time) was set to 10 seconds.

  As shown in FIG. 25, when the peak current values were compared, they were substantially the same, and the fluctuation rate of each peak current value was determined to be 1.7% (very small difference).

  Therefore, when the analysis of the analyte 1a including the copper ion concentration is repeatedly performed, a relatively simple inter-analysis activation process (for example, without performing a process such as a pre-analysis activation process for each analysis operation) (for example, It has been found that a sufficiently high S / B ratio can be ensured and high-sensitivity and high-precision analysis can be maintained only by performing a short inter-analysis activation process). When the inter-analysis activation potential is about +1000 mV or more (preferably about +1400 mV or more in the third embodiment), the working electrode 2 is regenerated for each inter-analysis activation process, and the activated state is maintained. Therefore, it was found that the analysis has reproducibility.

Example 4
In Example 4, the copper ion concentration in the analysis target 1a was set to various values, and each analysis was performed. First, a sample S15 was obtained by using a 150 mM potassium chloride solution as a supporting electrolyte and a 10 mM acetate buffer solution (pH 4.5) and 0 to 400 nM copper ions.

  Then, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S15 is performed in the same manner as in Example 3, and then the sample S15 is subjected to the analysis operation by the potential holding process and the potential sweep process similar to those in Example 3. The current change characteristics with respect to the potential change were obtained, and the results of these current change characteristics are shown in FIGS. 26A to 27E for each copper ion concentration. In addition, each peak current value of each current change characteristic is shown in FIG. 28 as a characteristic line with respect to the copper ion concentration. Also in the present Example 4, the same inter-analysis activation process as in Example 3 was performed for each analysis operation (potential holding process, potential sweep process) of each copper ion concentration.

  As shown in the characteristic curves of FIGS. 26A to 27E, it can be read that each peak current is sufficiently large and clearly detected, and increases as the copper ion concentration increases. Further, as shown in FIG. 28, it can be read that the characteristic line of each peak current value with respect to the copper ion concentration has a good correlation when the correlation coefficient R2 is 0.99 or more and has a high linearity.

  Therefore, in the analysis as shown in FIG. 1, copper ions (for example, 0 to 400 nM copper ions) in the analysis target 1a can be sufficiently measured, and each peak current value characteristic line with respect to the copper ion concentration can be reliably measured. It was found that it can be applied as a high calibration curve. In addition, when the analysis of the analyte 1a having a different copper ion concentration is repeated, a relatively simple inter-analysis activation process (without the pre-analysis activation process for each analysis operation) ( For example, it has been proved that a sufficiently high S / B ratio can be ensured and high-sensitivity and high-precision analysis can be maintained only by performing a short inter-analysis activation process). When the inter-analysis activation potential is about +1000 mV or more (preferably about +1400 mV or more in the fourth embodiment), the working electrode 2 is regenerated for each inter-analysis activation process, and the activated state is maintained. Therefore, it was found that the analysis has reproducibility.

(Example 5)
In Example 5, the copper ion concentration in the analysis target 1a was set to be relatively low, and each analysis was performed. First, a sample S16 was obtained by using a 150 mM potassium chloride solution as a supporting electrolyte and a 10 mM acetate buffer solution (pH 4.5) and 0 to 30 nM copper ions.

  Then, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S16 is performed in the same manner as in Example 3. Then, the sample S16 is subjected to the analysis operation by the potential holding process and the potential sweep process similar to those in Example 3. FIG. 29 shows the current change characteristics with respect to the potential change, and shows the peak current values of the current change characteristics as characteristic lines with respect to the copper ion concentration. Also in Example 5, the same inter-analysis activation process as in Example 3 was performed for each analysis operation (potential holding step, potential sweeping step) of each copper ion concentration.

  As shown by the characteristic line in FIG. 29, each peak current value increases as the copper ion concentration increases, and it can be read that the characteristic line has sufficient linearity.

  Therefore, in the analysis as shown in FIG. 1, even if the copper ion concentration is relatively low (for example, about 0 to 30 nM), the copper ion in the analyte 1a can be sufficiently measured. It was found that each peak current value characteristic line with respect to the concentration can be sufficiently applied as a reliable calibration curve. In the potential holding step, when the holding time of the potential of the working electrode 2 (that is, the reduction concentration time) is set longer than 180 seconds, it is possible to measure and analyze copper ions at an extremely low concentration (several hundred pM level). I confirmed that there was.

  In addition, when the analysis of the analyte 1a having a different copper ion concentration is repeated, a relatively simple inter-analysis activation process (without the pre-analysis activation process for each analysis operation) ( For example, it has been proved that a sufficiently high S / B ratio can be ensured and high-sensitivity and high-precision analysis can be maintained only by performing a short inter-analysis activation process). When the inter-analysis activation potential is about +1000 mV or more (preferably about +1400 mV or more in the fifth embodiment), the working electrode 2 is regenerated for each inter-analysis activation process, and the activated state is maintained. Therefore, it was found that the analysis has reproducibility.

(Example 6)
In Example 6, the copper ion concentration in the analysis target 1a was set to be relatively high, and each analysis was performed. First, a sample S17 was obtained by using a 150 mM potassium chloride solution as a supporting electrolyte and a 10 mM acetate buffer solution (pH 4.5) and 0 to 7 μM copper ions.

  Then, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S17 is performed in the same manner as in Example 3. Then, the sample S17 is subjected to the analysis operation by the potential holding process and the potential sweep process in the same manner as in Example 3. FIG. 30 shows current change characteristics with respect to potential changes, and shows peak current values of the current change characteristics as characteristic diagrams with respect to the copper ion concentration. Also in Example 6, the same inter-analysis activation process as in Example 3 was performed for each analysis operation (potential holding step, potential sweeping step) of each copper ion concentration.

  As shown in the characteristic diagram of FIG. 30, each peak current value increases as the copper ion concentration increases. For example, a characteristic line of about 0 to 3 μM has sufficient linearity, and the characteristic line is calibrated. It turns out that it can be applied sufficiently as a line.

  Therefore, in the analysis as shown in FIG. 1, even if the copper ion concentration is relatively high (for example, about 0 to 3 μM), the copper ion in the analyte 1a can be sufficiently measured. It was found that each peak current value characteristic line with respect to the concentration can be sufficiently applied as a reliable calibration curve. In the potential holding step, when the holding time of the potential of the working electrode 2 (that is, the reduction concentration time) is set shorter than 180 seconds, it is possible to measure and analyze copper ions at extremely high concentrations (several tens of μM level). I confirmed that there was.

  In addition, when the analysis of the analysis target 1a having a high copper ion concentration is repeatedly performed, a relatively simple inter-analysis activation process (e.g., without performing a pre-analysis activation process for each analysis operation) For example, it has been proved that a sufficiently high S / B ratio can be ensured and high-sensitivity and high-precision analysis can be maintained only by performing a short inter-analysis activation process). When the inter-analysis activation potential is about +1000 mV or more (preferably about +1400 mV or more in the sixth embodiment), the working electrode 2 is regenerated for each inter-analysis activation process, and the activated state is maintained. Therefore, it was found that the analysis has reproducibility.

(Example 7)
In Example 7, the working electrode 2 immersed in the analyte 1a containing mercury ions (in the presence of chloride ions) 1a is subjected to pre-analysis activation treatment at various pre-analysis activation potentials, and each analysis is performed. did. First, using a 25 mM potassium chloride solution as a supporting electrolyte, a 10 mM acetate buffer solution (pH 3.5) and 200 nM mercury ions were blended to obtain sample S18.

  Thereafter, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S18 was performed by setting the pre-analysis activation potential from 0 to +1800 mV and the pre-analysis activation time of 30 seconds. Then, the sample S18 is subjected to the analysis operation by the potential holding step (the potential of the working electrode 2 is held at +300 mV) and the potential sweep step in the same manner as in Example 1 to obtain the current change characteristics with respect to the potential change, and the results are analyzed. The preactivation potential is shown in FIGS. 31A to 32C. The potentials (0 mV to +1800 mV) in each of FIGS. 31A to 32C indicate the pre-analysis activation potential.

  As shown in the characteristic curves of FIGS. 31A to 32C, each peak current is detected with a sufficient magnitude, and as the pre-analysis activation potential goes from about +1000 mV to the positive side, the BG current decays and each peak It can be seen that the current is clear and sharp. It can be seen that this tendency (activation reaction) becomes stronger as the pre-analysis activation potential increases from about +1400 mV to the positive direction.

  This may be because the S / B ratio is increased by the pre-analysis activation treatment and the electrode reaction rate is improved. In addition, since chloride ions coexist in the sample S18, when the pre-analysis activation potential is about +1000 mV or more, the working electrode 2 is regenerated (for example, the working electrode 2 as shown in the verification example 1). It can be seen that the material can be regenerated by electropolishing before the start of the analysis when it has deteriorated. Furthermore, from the results of Verification Example 1 and Example 7 (and Example 1), the oxidation elution reaction tends to be suppressed as the pre-analysis activation potential is shifted from about +1400 mV to the positive direction side. It can be read that the activation reaction is higher.

  Even if the pre-analysis activation potential is a high potential exceeding +1800 mV (for example, a level exceeding +2 V), the S / B ratio is increased, the BG current is attenuated, and each peak current is clear and sharp. However, there is a possibility that bubbles may be generated on the surface of the working electrode 2.

  Therefore, in the analysis as shown in FIG. 1, before the potential holding step, for example, a pre-analysis activation potential of +1000 mV or higher with respect to the working electrode 2 in the presence of chloride ions (preferably from +1400 mV in Example 7). Applying about +2000 mV (potential immediately before bubbles are generated from the working electrode)), pre-analysis activation treatment not only stabilizes the BG current but also attenuates it, and a clearer peak current is detected. Thus, it was found that analysis with higher sensitivity and higher accuracy is possible. When the pre-analysis activation potential in the pre-analysis activation process is about +1000 mV or more (preferably about +1400 mV to +2000 mV in Example 7), the working electrode 2 is regenerated during the pre-analysis activation process. It was proved to have reproducibility of analysis because it was processed (regeneration treatment before the start of analysis) and the activated state was maintained.

(Example 8)
In the present Example 8, as in Example 7, the working electrode 2 immersed in the analysis target 1a containing mercury ions (in the presence of chloride ions) 1a is subjected to pre-analysis activation treatment at various pre-analysis activation potentials. Alternatively, polishing was performed (the surface was polished without performing pre-analysis activation (the working electrode 2 made of a gold electrode was buffed with alumina) and each analysis was performed. Sample S18a was obtained by using the solution as a supporting electrolyte and blending 20 ppb mercury ions.

  Thereafter, when the pre-analysis activation treatment of the working electrode 2 immersed in the sample S18a was performed, the pre-analysis activation potential was set to +0.8 to +2.0 V, and the pre-analysis activation time was set to 5 minutes. Then, the sample S18a is subjected to an analysis operation by the same potential holding step (the potential of the working electrode 2 is held at +300 mV) and the potential sweep step (sampling condition: 15 ms integration) as in Example 7, and the current change characteristic with respect to the potential change is obtained. Each was calculated | required and those results were shown in FIG.

  As shown in FIG. 33, although the peak current is detected in each condition, the BG current is not sufficiently attenuated when the working electrode 2 is subjected only to the polishing treatment and the activation potential before analysis is + 0.8V. It can be read that. On the other hand, when the pre-analysis activation potential is +1.2 V to +2.0 V (particularly when +1.2 V or +2.0 V), the BG current is sufficiently attenuated and each peak current becomes clear and sharp. It can be read that the same result as in Example 7 was obtained.

  Referring to Verification Example 1, when the pre-analysis activation potential is +1.2 V, the working electrode 2 may be consumed relatively quickly because the oxidation elution reaction of the working electrode is relatively large. In addition, when the pre-analysis activation potential is +1.8 V, the consumption of the working electrode 2 is suppressed as compared with the case where the pre-analysis activation potential is +1.2 V, but an oxide film can be formed. It is conceivable that the attenuation of is suppressed. Furthermore, even when the pre-analysis activation potential is a high potential exceeding +2.0 V, there is a possibility that the S / B ratio is increased, the BG current is attenuated, and each peak current is clear and sharp.

  Therefore, in the analysis as shown in FIG. 1, the pre-analysis activation potential of +1.2 V or more with respect to the working electrode 2 in the presence of chloride ions in the pre-stage of the potential holding step (in Example 8, for example, In consideration of suppressing the consumption of the working electrode, the BG current is preferably attenuated as well as stabilized by applying a pre-analysis activation process by applying a potential in the positive direction (preferably about +1.8 V), Since a clearer peak current was detected, it was found that analysis with higher sensitivity and higher accuracy was possible. When the pre-analysis activation potential in the pre-analysis activation treatment is such that an oxidative elution reaction of the working electrode occurs (in this Example 8, about +1.2 mV to +2.0 V), the pre-analysis activity It was found that the working electrode 2 was regenerated (regenerated before the start of analysis) during the activation process and the activated state was maintained, so that the analysis was reproducible.

Example 9
In Example 9, the activation time before analysis was set to various times, and the analysis for the sample S18 was performed. First, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S18 was performed by setting the pre-analysis activation potential + 1800 mV and the pre-analysis activation time of 0 seconds to 180 seconds. Then, the sample S18 is subjected to the analysis operation in the same potential holding step and potential sweeping step as in Example 7 to obtain the current change characteristic with respect to the potential change, and the result of each current change characteristic is obtained for each activation time before analysis. 34A to 34D.

  As shown in FIG. 34A to FIG. 34D, each peak current of each characteristic curve is detected with a sufficient magnitude, and as the pre-analysis activation time becomes longer, the BG current decays and each peak current becomes clear. I can read that Even if the pre-analysis activation time is set to more than 180 seconds, the BG current may be substantially constant or further attenuated, but the analysis time may be prolonged.

  Therefore, in the analysis as shown in FIG. 1, the BG current is sufficiently attenuated by setting the pre-analysis activation time to a predetermined time (preferably, for example, 180 seconds in this embodiment 9), and a sufficiently clear peak current is detected. Therefore, it was found that analysis with higher sensitivity and higher accuracy is possible.

(Example 10)
In Example 10, after performing the pre-analysis activation process as described above on the analyte 1a containing mercury ions for the sample S18, the analysis operation including the potential holding step and the potential sweep step is repeatedly performed. Analysis was performed. First, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S18 was performed by setting the pre-analysis activation potential + 1800 mV and the pre-analysis activation time of 180 seconds. Then, for the sample S18, the analysis operation by the potential holding process and the potential sweep process similar to those in Example 7 is repeated five times to obtain current change characteristics for each potential change, and each peak current of each current change characteristic is obtained. The values are shown in FIG. 35 for each analysis operation. In this Example 10, the inter-analysis activation process (inter-analysis activation potential + 1400 mV, inter-analysis activation time) similar to that in Example 3 for each analysis operation (potential holding step, potential sweep step) of each copper ion concentration. 10 seconds).

  As shown in FIG. 35, when the peak current values were compared, they were substantially the same, and the fluctuation rate of each peak current value was determined to be 0.2% (very small difference).

  Therefore, when the analysis of the analyte 1a including the mercury ion concentration is repeatedly performed, a relatively simple inter-analysis activation process (for example, without performing a process such as a pre-analysis activation process for each analysis operation) (for example, It has been found that a sufficiently high S / B ratio can be ensured and high-sensitivity and high-precision analysis can be maintained only by performing a short inter-analysis activation process). When the inter-analysis activation potential is about +1000 mV or more (preferably about +1400 mV or more in the tenth embodiment), the working electrode 2 is regenerated for each inter-analysis activation process, and the activated state is maintained. Therefore, it was found that the analysis has reproducibility.

(Example 11)
In Example 11, the mercury ion concentration in the analysis target 1a was set to various values, and each analysis was performed. First, a sample S19 was obtained by using a 25 mM potassium chloride solution as a supporting electrolyte and a 10 mM acetate buffer solution (pH 3.5) and 0 to 50 nM mercury ions.

  Then, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S19 is performed in the same manner as in Example 10, and then the potential holding step (the holding time of the potential of the working electrode 2) in the same manner as in Example 10 is applied to the sample S19. Is set to 300 seconds), the current change characteristics with respect to the potential change are obtained by performing the analysis operation by the potential sweep process, and the characteristic diagram with respect to the mercury ion concentration in each peak current value of each current change characteristic is shown in FIG. In Example 11 as well, the same inter-analysis activation process as in Example 10 was performed for each analysis operation (potential holding step, potential sweeping step) of each mercury ion concentration.

  As shown in the characteristic diagram of FIG. 36, it can be seen that each peak current is sufficiently large and clearly detected, and increases as the mercury ion concentration increases. Further, as shown in FIG. 36, it can be read that the characteristic line of each peak current value with respect to the mercury ion concentration has a good correlation and a high linearity when the correlation coefficient R2 is 0.99 or more.

  Therefore, in the analysis as shown in FIG. 1, mercury ions (for example, 0 to 50 nM mercury ions) in the analyte 1a can be sufficiently measured, and each peak current value characteristic line with respect to the mercury ion concentration is reliable. It was found that it can be applied as a high calibration curve. In addition, when the analysis of the analyte 1a having a different mercury ion concentration is repeated, a relatively simple inter-analysis activation process (without the pre-analysis activation process for each analysis operation) is performed. For example, it has been proved that a sufficiently high S / B ratio can be ensured and high-sensitivity and high-precision analysis can be maintained only by performing a short inter-analysis activation process). When the inter-analysis activation potential is about +1000 mV or more (preferably about +1400 mV or more in the embodiment 11), the working electrode 2 is regenerated for each inter-analysis activation process, and the activated state is maintained. Therefore, it was found that the analysis has reproducibility.

(Example 12)
In Example 12, the mercury ion concentration in the analysis target 1a was set to be relatively low, and each analysis was performed. First, a sample S20 was obtained by using a 25 mM potassium chloride solution as a supporting electrolyte and a 10 mM acetate buffer solution (pH 3.5) and 0 to 4.5 nM mercury ions.

  Then, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S20 is performed in the same manner as in Example 10, and then the sample S20 is subjected to the analysis operation by the potential holding process and the potential sweep process similar to those in the Example 11. FIG. 37 shows the current change characteristics with respect to the potential change, and the peak current values of these current change characteristics are shown as characteristic lines with respect to the copper ion concentration. Also in the present Example 12, the same inter-analysis activation process as in Example 10 was performed for each analysis operation (potential holding process, potential sweep process) of each copper ion concentration.

  As shown in the characteristic line of FIG. 37, each peak current value increases as the copper ion concentration increases, and the correlation coefficient R2 is 0.98 or more, and has a good correlation. It can be read that it has sex.

  Therefore, in the analysis as shown in FIG. 1, even if the mercury ion concentration is relatively low (for example, about 0 to 4.5 nM), the mercury ion in the analyte 1a can be sufficiently measured. It was found that each peak current value characteristic line for copper ion concentration can be applied as a highly reliable calibration curve. In the potential holding step, when the holding time of the potential of the working electrode 2 (that is, the reduction concentration time) is set longer than 300 seconds, it is possible to measure and analyze mercury ions at a very low concentration (several hundred pM level). I confirmed that there was.

  In addition, when the analysis of the analyte 1a having a different mercury ion concentration is repeated, a relatively simple inter-analysis activation process (without the pre-analysis activation process for each analysis operation) is performed. For example, it has been proved that a sufficiently high S / B ratio can be ensured and high-sensitivity and high-precision analysis can be maintained only by performing a short inter-analysis activation process). When the inter-analysis activation potential is about +1000 mV or more (preferably about +1400 mV or more in the embodiment 12), the working electrode 2 is regenerated for each inter-analysis activation process, and the activated state is maintained. Therefore, it was found that the analysis has reproducibility.

(Example 13)
In Example 13, the mercury ion concentration in the analyte 1a was set to be relatively high, and each analysis was performed. First, a sample S21 was obtained by using a 150 mM potassium chloride solution as a supporting electrolyte and a 10 mM acetate buffer solution (pH 4.5) and 0 to 500 nM mercury ions.

  Then, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S21 is performed in the same manner as in Example 10, and then the sample S21 is subjected to the analysis operation by the potential holding process and the potential sweep process similar to those in Example 11. The current change characteristics with respect to the potential change were obtained, and each peak current value of each current change characteristic was shown in FIG. 38 as a characteristic line with respect to the copper ion concentration. In Example 13, the same inter-analysis activation process as in Example 10 was performed for each mercury ion concentration analysis operation (potential holding step, potential sweep step).

  As shown in the characteristic line of FIG. 38, each peak current value increases as the mercury ion concentration increases. For example, if it is about 0 to 150 nM, the linearity is sufficient, and the characteristic line is sufficient as a calibration curve. It turns out that it is applicable.

  Therefore, in the analysis as shown in FIG. 1, even if the mercury ion concentration is relatively high (for example, about 0 to 150 nM), the mercury ion in the analyte 1a can be sufficiently measured. It was found that each peak current value characteristic line with respect to the concentration can be sufficiently applied as a reliable calibration curve. In the potential holding step, when the holding time of the potential of the working electrode 2 (that is, the reduction concentration time) is set to be shorter than 300 seconds, it is possible to measure and analyze extremely high concentration (several tens of μM level) mercury ions. I confirmed that there was.

  In addition, when the analysis of the analyte 1a having different mercury ion concentrations is repeated, a relatively simple inter-analysis activation process (without the pre-analysis activation process for each analysis operation) ( For example, it has been proved that a sufficiently high S / B ratio can be ensured and high-sensitivity and high-precision analysis can be maintained only by performing a short inter-analysis activation process). Further, when the inter-analysis activation potential is about +1000 mV or more (preferably about +1400 mV or more in the embodiment 13), the working electrode 2 is regenerated for each inter-analysis activation process, and the activated state is maintained. Therefore, it was found that the analysis has reproducibility.

(Example 14)
In the fourteenth embodiment, the working electrode 2 immersed in the analysis target 1a containing arsenic ions (in the presence of chloride ions) 1a is subjected to pre-analysis activation treatment or polishing treatment (before analysis) at various pre-analysis activation potentials. The surface was polished without performing the activation treatment (the working electrode 2 made of a gold electrode was buffed with alumina) and each analysis was performed. In Example 14, HZ-5000 (HAG3001) manufactured by Hokuto Denko Co., Ltd. was used as the potentiostat 5. First, a 1M hydrochloric acid solution was used as a supporting electrolyte, and 60 ppb arsenic ions were blended to obtain a sample S22.

  Thereafter, when the pre-analysis activation treatment of the working electrode 2 immersed in the sample S22 was performed, the pre-analysis activation potential was set to +0.8 to +3.0 V, and the pre-analysis activation time was set to 5 minutes. And about the sample S22, the analysis operation by the electric potential holding process and electric potential sweep process similar to Example 8 was performed, the electric current change characteristic with respect to an electric potential change was each calculated | required, and those results were shown to FIG. 39A, B, and FIG.

  As a comparative example, a gold-plated carbon electrode (a carbon electrode (glassy carbon electrode with a diameter of 3 mm (manufactured by BAS)) in a 1000 ppm gold-plated bath) is immersed in the working electrode 2 and a potential of −0.4 V is applied for 15 minutes. The sample S22 was subjected to an analysis operation (analysis operation without performing the pre-analysis activation process) in the potential holding process and the potential sweep process similar to those of Example 8, and the current change characteristic with respect to the potential change was obtained. The results are shown in FIG.

  As shown in FIGS. 39A to 41, when a gold-plated carbon electrode is used as the working electrode, when the working electrode 2 is only polished, and when the activation potential before analysis is +0.8 V to +2.0 V, Peak current is detected. However, when the gold-plated carbon electrode is used, it can be read that the BG current is insufficiently attenuated when only the polishing treatment is performed and the activation potential before analysis is + 0.8V.

  On the other hand, when the pre-analysis activation potential is +1.2 V to +2.0 V (particularly when +1.2 V or +2.0 V), the BG current is sufficiently attenuated and each peak current becomes clear and sharp. It can be read that the same result as in Example 8 was obtained.

  Referring to Verification Example 1, when the pre-analysis activation potential is +1.2 V, the working electrode 2 may be consumed relatively quickly because the oxidation elution reaction of the working electrode is relatively large. Further, when the pre-analysis activation potential is +1.8 V, the consumption of the working electrode 2 is suppressed as compared with the case where the pre-analysis activation potential is +1.2 V, but the attenuation of the BG current is suppressed. Can be considered. Furthermore, when the pre-analysis activation potential exceeds +2.0 V (+2.5 V, +3.0 V in Example 14), the BG current is attenuated, but arsenic ions are not reduced and concentrated. Can be considered.

  Therefore, in the analysis as shown in FIG. 1, the pre-analysis activation potential (for example, +1.2 V or more) with respect to the working electrode 2 in the presence of chloride ions in the pre-stage of the potential holding step (in Example 14, for example, In consideration of suppressing the consumption of the working electrode, the pre-analysis activation process is preferably performed by applying about +1.8 V to +2.0 V (potential immediately before bubbles (oxygen, chlorine, etc.) are generated from the working electrode). By performing the above, the BG current is not only stabilized but also attenuated, and a clearer peak current is detected. Thus, it has been found that analysis with higher sensitivity and higher accuracy is possible. In addition, when the pre-analysis activation potential in the pre-analysis activation treatment is such that an oxidative elution reaction of the working electrode occurs (in Example 14, about +1.2 V to +2.0 V), the pre-analysis activity It was found that the working electrode 2 was regenerated (regenerated before the start of analysis) during the activation process and the activated state was maintained, so that the analysis was reproducible.

(Example 15)
In Example 15, the arsenic ion concentration in the analysis target 1a was set to various values, and each analysis was performed. In Example 15, a mercury-free voltammetric analyzer FIELDER HOE-100 manufactured by Hokuto Denko Co., Ltd. was used as the potentiostat 5. First, a 1M hydrochloric acid solution was used as a supporting electrolyte, and 0-100 ppb arsenic ions were blended to obtain a sample S23. Thereafter, the pre-analysis activation treatment of the working electrode 2 immersed in the sample S23 was performed by setting the pre-analysis activation potential +1.2 V and the pre-analysis activation time of 5 minutes.

  And about the sample S23, the analysis operation by the electric potential holding process similar to Example 8 and an electric potential sweep process were performed, the current change characteristic with respect to an electric potential change was each calculated | required, and those results were shown to FIG. 42A. 42B and 42C show the respective peak areas and the respective peak current values of the respective current change characteristics as characteristic lines with respect to the arsenic ion concentration.

  Further, as a comparative example, the gold-plated carbon electrode is used as the working electrode 2 and the sample S23 is analyzed by the same potential holding step and potential sweeping step as in Example 8 (analysis operation without performing pre-analysis activation processing). The current change characteristics with respect to the potential change were obtained, and the results are shown in FIG.

  As shown in FIGS. 42A and 43, peak currents corresponding to arsenic ion concentrations are detected, respectively. However, when gold-plated carbon electrodes are used, the attenuation of the BG current is insufficient and the BG currents overlap in a complicated manner. Therefore, it can be read that it is difficult to calculate the peak current.

  On the other hand, when the gold electrode is used, the BG current is sufficiently attenuated and each peak current becomes clear and sharp, and it can be read that the same result as in Example 8 is obtained. Further, as shown in FIGS. 42B and 42C, the correlation coefficient R2 of each characteristic line has a good correlation with 0.99 or more. For example, in the case of a peak area, about 0 to 160 ppb, and in the case of a peak current value It has been found that if it is about 0 to 100 ppb, it has sufficient linearity, and the characteristic line can be sufficiently applied as a calibration curve.

  Therefore, in the analysis as shown in FIG. 1, arsenic ions (for example, arsenic ions of several ppb to several hundred ppb level) in the analysis target 1a can be sufficiently measured, and each peak area characteristic line with respect to the arsenic ion concentration, It was found that each peak current value characteristic line can be applied as a highly reliable calibration curve.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

  For example, it is composed of at least a working electrode (working electrode made of a gold electrode), a counter electrode, and a reference electrode, and each of the electrodes is arranged in an analysis target, and the potential of the working electrode is held at a predetermined potential by a potential holding step. If the potential change of the working electrode can be detected while the potential of the working electrode is swept to the high potential side in the potential sweeping step, it is appropriately within the scope of common technical knowledge. Even if a design change (for example, change of each electrode form, analysis condition (for example, differential pulse mode, linear sweep mode), etc.), etc., etc., the same effect as the present embodiment can be obtained. Is clear.

Schematic explanatory drawing of the apparatus applicable to the solution analysis method in this Embodiment. Cyclic voltammogram of verification example 1 (samples S1 to S3). The cyclic voltammogram of verification example 1 (sample S1a). The electric current change characteristic view with respect to the electric potential change of the verification example 2 (in the case of a potassium chloride solution (0-100 nM) and a linear sweep mode). The electric current change characteristic view with respect to the electric potential change of the verification example 2 (in the case of a potassium chloride solution (120-200 nM) and a linear sweep mode). The electric current change characteristic view with respect to the electric potential change of the verification example 2 (in the case of a potassium sulfate solution (0-100 nM)). The electric current change characteristic view with respect to the electric potential change of the verification example 2 (in the case of a potassium sulfate solution (120-200 nM)). The characteristic diagram of the peak current with respect to the copper ion concentration of Verification Example 2 (in the case of a potassium sulfate solution). The electric current change characteristic view with respect to the electric potential change of the verification example 2 (in the case of a potassium nitrate solution (0-100 nM)). The electric current change characteristic view with respect to the electric potential change of the verification example 2 (in the case of a potassium nitrate solution (120-200 nM)). The characteristic diagram of the peak current with respect to the copper ion concentration of Verification Example 2 (in the case of a potassium nitrate solution). The electric current change characteristic view with respect to the electric potential change of the verification example 2 (in the case of a potassium chloride solution (0-50 nM) and differential pulse mode). The electric current change characteristic view with respect to the electric potential change of the verification example 2 (in the case of a potassium chloride solution (60-160 nM) and differential pulse mode). The electric current change characteristic view with respect to the electric potential change of the verification example 2 (in the case of a potassium chloride solution (180-200 nM) and differential pulse mode). The characteristic diagram of the peak current with respect to the copper ion concentration of Verification Example 2 (in the case of potassium chloride solution and differential pulse mode). The peak current (peak current value) characteristic diagram with respect to the potassium chloride concentration in Verification Example 3 (in the case of copper ions). The peak current (peak current value) characteristic diagram with respect to the potassium chloride concentration in Verification Example 3 (in the case of mercury ions). The peak current value characteristic view with respect to pH of the buffer solution of Verification Example 4 (in the case of copper ions). The peak current value characteristic view with respect to pH of the buffer solution of Verification Example 4 (in the case of mercury ions). The electric current change characteristic view with respect to the electric potential change of the verification example 5 (in the case of copper ion and lead ion). The electric current change characteristic view with respect to the electric potential change of the verification example 5 (in the case of mercury ion and copper ion). The electric current change characteristic view with respect to the electric potential change of Example 1 (in the case of the copper ion and the activation potential before analysis 700-1200 mV). FIG. 4 is a current change characteristic diagram with respect to potential change in Example 1 (in the case of copper ions, pre-analysis activation potential of 1300 to 1600 mV). The electric current change characteristic view with respect to the electric potential change of Example 2 (in the case of copper ion). The peak current value characteristic figure for every analysis operation of Example 3 (in the case of copper ion). The electric current change characteristic with respect to the electric potential change of Example 4 and a calibration curve (in the case of a copper ion (0-200 nM)). The electric current change characteristic with respect to the electric potential change of Example 4 and a calibration curve (in the case of a copper ion (240-400 nM)). The characteristic line figure of the peak current to the copper ion concentration of Example 4. The characteristic line figure of the peak current to the copper ion concentration of Example 5. The characteristic line figure of the peak current to the copper ion concentration of Example 6. The electric current change characteristic view with respect to the electric potential change of Example 7 (in the case of mercury ion and activation potential before analysis of 0 to 1600 mV). The current change characteristic view with respect to the potential change of Example 7 (in the case of mercury ion, activation potential before analysis 1400 to 1800 mV). The electric current change characteristic view with respect to the electric potential change of Example 8 (in the case of mercury ion and 0.1 M hydrochloric acid solution as a supporting electrolyte). The current change characteristic view with respect to the potential change of Example 9 (in the case of mercury ion). The peak current value characteristic figure for every analysis operation of Example 10 (in the case of mercury ion). The characteristic line figure of the peak current with respect to the mercury ion concentration of Example 11. The characteristic line figure of the peak current with respect to the mercury ion concentration of Example 12. The characteristic line figure of the peak current with respect to the mercury ion concentration of Example 13. The current change characteristic view with respect to the potential change of Example 14 (in the case of arsenic ions). The S / B ratio characteristic figure with respect to the activation potential before analysis of Example 14 (in the case of arsenic ion). The S / B ratio characteristic figure with respect to the activation potential before the analysis of the comparative example in Example 14 (Example, in the case of a gold plating carbon electrode). The electric current change characteristic with respect to the electric potential change of Example 15, a peak area characteristic, and a peak electric current value characteristic figure (in the case of arsenic ion). The electric current change characteristic view with respect to the electric potential change of the comparative example in Example 15 (in the case of a gold plating carbon electrode).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Container 1a ... Analyte 2 ... Working electrode 3 ... Counter electrode 4 ... Reference electrode 5 ... Potentiostat 6 ... Computer 7 ... Stirrer

Claims (7)

After placing the working electrode, counter electrode, and reference electrode in the analyte,
A potential holding step of holding the potential of the working electrode at a potential that can be reduced by the measurement target in the analyte;
A potential sweeping step of detecting a current change with respect to a potential change in the working electrode while sweeping the held potential of the working electrode in a positive direction in which the measurement target in the analysis target can be oxidized. A method of performing an operation,
A gold electrode is used as the working electrode, and before the analysis operation, a pre-analysis activation potential is applied by applying a pre-analysis activation potential in a solution containing chloride ions or an analyte in the presence of chloride ions. Process
The analytical procedures of the, are performed by the state chloride ions coexisting in the analyte above,
The solution analysis method, wherein the pre-analysis activation potential is a potential at which a gold electrode undergoes an oxidation elution reaction in the presence of chloride ions . 2. The solution analysis method according to claim 1 , wherein the pre-analysis activation potential excludes a potential at which oxygen and chlorine bubbles are generated from the potential that causes the oxidation elution reaction. 3. The solution analysis method according to claim 2, wherein the pre-analysis activation potential is in a range excluding the potential at which an oxide film is formed on the gold electrode surface in the presence of chloride ions. When repeating the analysis operation of the, between the analysis operation, any one of the claims 1 to 3, characterized in that the application to analyze between activation analysis between activating potential to the working electrode The solution analysis method described in 1. 5. The solution according to claim 4, wherein the inter-analysis activation potential excludes a potential at which oxygen and chlorine bubbles are generated from a potential at which the gold electrode undergoes an oxidation elution reaction in the presence of chloride ions. Analysis method. 6. The solution analysis method according to claim 5, wherein the inter-analysis activation potential is a potential at which an oxide film is formed on the gold electrode surface in the presence of chloride ions. The solution analysis method according to claim 1 , wherein the measurement object includes at least one of mercury, copper, and arsenic.

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