JP3810760B2 - SOLUTION ANALYZER AND ITS REPRODUCTION METHOD, SOLUTION ANALYSIS METHOD - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a solution analyzer that can be quantitatively analyzed by voltammetry comprising a working electrode, a counter electrode, and a reference electrode, a regeneration method thereof, and a solution analysis method. The present invention relates to an apparatus and a method capable of analyzing an analysis object.
[0002]
[Prior art]
At present, survey results have been announced that lead pipes are used in approximately 77% of the water supply companies with a water supply population of 50,000 or more (approximately 35.8 million units).
[0003]
Lead is pointed out to have a great influence on human health, for example, and its water quality standard is to be strengthened from the current 0.05 mg / l to 0.01 mg / l in 2003. In addition, as a use type of the lead pipe, the one using the tap from the distribution pipe branch point on the public road to the tap side of the tap water consumer side (hereinafter simply referred to as residential land), or the distribution pipe branch point on the public road There are various types of use, such as those used from around the meter in the residential area, or those used only around the meter.
[0004]
Therefore, the Waterworks Bureau is actively working on water leakage prevention measures as one of the most important measures as part of the effective use of water resources, but more than 95% of water leakage is in the residential land that is the property of customers. Most of the water is leaked from the lead pipe. For this reason, as countermeasures against lead elution from lead water pipes and water leakage prevention, material improvement work has been implemented to replace the lead water pipes up to the water meter in the residential area with stainless steel pipes or vinyl chloride pipes, preventing the occurrence of water leakage. Strive to maintain health.
[0005]
On the other hand, with the strengthening of the water quality standard, research and development of a method capable of measuring low-concentration lead (for example, lead eluted from the inner surface of a lead pipe in still water) has been performed. Generally, flame atomic absorption method, flameless atomic absorption method, ICP emission spectroscopic analysis method (for example, ultrasonic nebulizer) and the like are applied to measure low concentration lead in drinking water. However, each of the above methods is not generally handled because the apparatus used is large and expensive, and requires technical skill in the operation of the apparatus.
[0006]
In addition, as a method of electrochemically analyzing a metal (electrochemically active substance) in a solution, a method of quantitative analysis by voltammetry is generally applied, and for example, a platinum electrode, a gold electrode, A carbon electrode, a solid electrode made of an inert metal such as silver, or an electrode using a mercury drop (hereinafter referred to as a mercury electrode) is used.
[0007]
FIG. 24 is a schematic explanatory view showing an example of a solution analyzer by voltammetry using a generally known solid electrode. In FIG. 24, reference numeral 1 denotes a measurement container. The measurement container 1 contains a sample solution 1a containing metal ions to be analyzed and is sealed by a sealing member 1b. Reference numeral 2 indicates a working electrode (for example, a solid electrode such as a platinum electrode, a gold electrode, a carbon electrode, or an electrode coated with a thin film such as silver), and reference numeral 3 indicates a counter electrode (for example, an electrode made of platinum or carbon). The working electrode 2 and the counter electrode 3 are provided so as to be immersed in the sample liquid 1a in the measurement container 1 with a certain distance therebetween.
[0008]
Reference numeral 4 denotes a potentiostat, and the working electrode 2 and the counter electrode 3 are connected to the potentiostat 4 via respective wirings 2a and 3a. The potentiostat 4 is connected to a potential sweeper 4a, a recorder 4b, etc. as necessary. Reference numeral 5 denotes a reference electrode (a reference electrode; for example, a saturated calomel electrode or an Ag / AgCl electrode), which is electrically connected to the working electrode 2 via a capillary 5a and is wired. It is connected to the potentiostat 4 through 5b.
[0009]
Reference numeral 6 denotes nitrogen gas (N ₂ ) In the vicinity of the counter electrode 3 and a supply pipe for removing dissolved oxygen in the sample liquid 1a. 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 sample liquid 1 a in the measurement container 1. In the electrochemical analysis method, when a very low concentration substance is analyzed, an anode (or cathode) stripping voltammetry method is generally applied.
[0010]
Next, a metal analysis method using the analyzer shown in FIG. 24 will be described. First, with respect to the sample solution 1a in advance, masking (addition of a desired masking agent) to prevent each metal ion in the sample solution 1a from interfering with each other and affecting the analysis, pH adjustment by adding a buffer solution, The dissolved oxygen is removed (deaeration process).
[0011]
Thereafter, in order to promote the movement of the substance to be analyzed to the surface of the working electrode 2, the sample liquid 1a is stirred (turbulent) through the stirrer 7 and the stirrer 7a to move the substance in the sample liquid 1a (electrochemistry). The potential of the working electrode 2 is set to a desired negative potential (potential lower than the natural electrode potential) by the potentiostat 4 while promoting the mass transfer of the active substance, and each metal ion in the sample solution 1a is Electrodeposition is performed on the surface of the working electrode 2 to form an electrodeposited substance (reduction concentration). Thereafter, the potentiostat 4 sweeps the potential of the working electrode 2 in the positive potential direction to oxidize and elute the electrodeposition substance into the sample solution 1a (anode stripping).
[0012]
Since each metal in the electrodeposition material is eluted at a predetermined oxidation potential, when each metal is eluted in the sample solution 1a, a current change (peak to potential) with respect to a potential change of the working electrode 2 occurs. Current) at a desired scanning speed. Then, the amount of electricity (coulomb amount) obtained by integral calculation of the current change is compared with a calibration curve, and the sample solution 1a can be analyzed (analysis of each metal ion concentration).
[0013]
FIG. 25 is a schematic explanatory view showing an example of a solution analyzer by voltammetry using a generally known mercury electrode. Components similar to those shown in FIG. 24 are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 25, reference numeral 8 indicates a working electrode (mercury electrode) using a mercury drop, and reference numeral 9 indicates a mercury pool.
[0014]
In the apparatus shown in FIG. 25, the working electrode 8 is set to a desired negative potential without masking or promoting mass transfer, and metal ions in the sample liquid 1a are reduced on the surface of the working electrode 8, The working electrode 8 is amalgamated. Thereafter, the potential of the amalgamated working electrode 8 is swept in the positive potential direction to oxidize and elute, and a quantitative analysis is performed by measuring the current with respect to the potential change. However, when the reduction potential is close, for example, Cd and In, Cd or Pb and Tl may interfere with each other. The former can be improved by using a mercury thin film electrode, while the latter requires the addition of a masking agent such as EDTA.
[0015]
According to the analyzer using the mercury electrode as shown in FIG. 25, since there is no need to perform masking and a wide potential window is provided, means for accelerating mass transfer such as a stirrer for the solution containing the analyte (hereinafter referred to as substance) The analysis can be performed in a stationary state without using a movement promoting means, and the concentration of the analyte (for example, the concentration of lead in tap water) cannot be analyzed by an analyzer using a solid electrode such as a carbon electrode. Even at the level, the object to be analyzed can be easily measured with high sensitivity and high accuracy. In addition, when a solid electrode is used, the working electrode surface becomes rough due to damage, etc. or deposits remain after each analysis, so that the working electrode surface is ground, polished, washed, etc. for each analysis (hereinafter referred to as “regeneration”). However, when a mercury electrode is used, the above operation is not necessary.
[0016]
For this reason, when analyzing a solution with a very low concentration of the analyte (for example, clean water containing lead with a low concentration (less than 100 nM)), an analyzer configured with a mercury electrode is used. It was.
[0017]
As a method for analyzing a solution having an analyte concentration of about 900 nM to 3000 nM, NaN was added to the sample solution in an analyzer as shown in FIG. ₂ SO _Four , HCl is added, and a method using an electrode made of copper as a working electrode has been reported (for example, see Non-Patent Document 1).
[0018]
[Non-Patent Document 1]
Daniel F. -Tibbets (Daniel F. Tibbetts), James Davis, Richard G.・ Compton (Richard G. Compton), “Sonoelectroanalytical Detection of Red at a Bear Copper Electrode”, (Germany) Fresenius' Journal Analytical Chemistry, Springer-Verlag, 2000, 368, p. 412-414.
[0019]
[Problems to be solved by the invention]
As described above, when a mercury electrode is used as the working electrode, there is a problem that the metal remains as an impurity in the mercury thin film due to amalgamation, and the reliability of the mercury electrode after analysis is lowered. Therefore, when analyzing using the mercury electrode repeatedly, it takes time to process impurities remaining in the mercury electrode for each analysis, and when using a new mercury electrode for each analysis, The cost required for analysis increases.
[0020]
Further, since mercury is extremely toxic and causes environmental pollution, problems have arisen in the treatment of mercury electrodes that can no longer be used.
[0021]
The present invention has been made on the basis of the above-mentioned problems, and can analyze an analyte to be analyzed at a very low concentration (for example, a concentration of about 1 nM to 100 nM) with high sensitivity and high accuracy without causing problems such as environmental pollution. An object of the present invention is to provide a solution analysis apparatus that can be easily analyzed and that can easily regenerate the apparatus after the analysis (regeneration of the working electrode), a regeneration method thereof, and a solution analysis method.
[0022]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention comprises at least a working electrode, a counter electrode, a reference electrode (for example, an Ag / AgCl reference electrode), and a mass transfer promoting means. Each of the electrodes is placed in a solution containing a target (for example, an electrochemically active substance such as lead ion), and an analyte to be analyzed electrodeposited by the working electrode is eluted in the solution to respond to potential changes. In the solution analyzer capable of detecting a change in current and analyzing an object to be analyzed of a level of 100 nM or less, the working electrode is made of copper.
[0023]
According to a second aspect of the present invention, in the first aspect of the present invention, the potential of the working electrode is set to a potential step (for example, the pulse height is greater than 0 mV and less than 50 mV, the pulse width is greater than 0 ms and less than 15 ms, and the pulse period is Sweeping in the positive potential direction while making the potential step greater than 0 ms and 100 ms or less) elutes the analyte electrodeposited on the working electrode.
[0024]
The invention according to claim 3 is the invention according to claim 1 or 2, wherein the area of the working electrode is 0.02 cm. ² It is the above.
[0025]
The invention according to claim 4 includes a step of disposing a working electrode, a counter electrode, and a reference electrode in a solution containing an object to be analyzed (for example, an electrochemically active substance such as lead ion), and a mass transfer promoting atmosphere. Maintaining the potential of the working electrode to a negative potential while maintaining the electrode to be analyzed on the surface of the working electrode, and sweeping the potential of the working electrode in the positive potential direction, And a step of detecting a current change with respect to a potential change at the working electrode while eluting the analysis object in the solution, wherein the working electrode is an electrode made of copper. To do.
[0026]
A fifth aspect of the invention is characterized in that, in the fourth aspect of the invention, the potential of the working electrode in the step of electrodeposition is defined according to the analyte to be analyzed contained in the solution.
[0027]
According to a sixth aspect of the invention, in the invention of the fourth or fifth aspect, the step of detecting a change in current sweeps the potential of the working electrode to a positive potential.
[0028]
The invention described in claim 7 is characterized in that, in the invention described in any one of claims 4 to 6, a step of degassing the solution is provided before the step of electrodeposition.
[0029]
The invention according to claim 8 is the invention according to any one of claims 4 to 6, wherein the step of detecting a change in current is performed by measuring the potential of the working electrode by a potential step (pulse height is greater than 0 mV but less than 50 mV, and pulse width is less than 0 ms. The voltage is swept in the positive potential direction while being stepped at a potential of 15 ms or less and a pulse period of greater than 0 ms and 100 ms or less.
[0030]
The invention according to claim 9 is the invention according to any one of claims 4 to 8, characterized in that 10 mM or more of an acetate buffer solution is added to the solution containing the analyte.
[0031]
A tenth aspect of the present invention is characterized in that, in the fourth to ninth aspects of the present invention, the pH of the solution containing the analyte is 4.75 or less.
[0032]
The invention according to claim 11 is the invention according to any one of claims 4 to 10, wherein the solution containing the analyte has an electric quantity of the working electrode in the step of detecting the current change of 50 × 10 5. ^-9 A KCl solution is added so as to be C or more.
[0033]
A twelfth aspect of the invention is characterized in that in the inventions of the fourth to eleventh aspects, ascorbic acid is added (for example, 200 μM added) to the solution containing the analyte.
[0034]
The invention according to claim 13 is composed of at least a working electrode, a counter electrode, a reference electrode, and a mass transfer promoting means, and the above-described solution is contained in a solution containing an analyte (for example, an electrochemically active substance such as lead ion). A current corresponding to a potential change while arranging each electrode and eluting the analyte electrodeposited by the working electrode into the solution (for example, elution by sweeping the potential of the working electrode in the positive potential direction while stepping the potential) In the method for regenerating a solution analyzer capable of detecting a change, the potential of the working electrode when the electrodeposited analyte is eluted into the solution is swept up to a positive potential. It is characterized by performing reproduction.
[0035]
According to a fourteenth aspect of the present invention, in the invention of the thirteenth aspect, the working electrode is regenerated by applying a positive potential to the working electrode at a constant potential and carrying out a predetermined time before performing the analysis by the solution analyzer. It is characterized by performing by doing.
[0036]
According to a fifteenth aspect of the invention, in the invention of the thirteenth or fourteenth aspect, the regeneration of the working electrode has a positive potential of less than 400 mV with respect to the working electrode (for example, less than 400 mV with respect to the Ag / AgCl reference electrode). It is characterized by being applied.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a solution analyzer, a regeneration method thereof, and a solution analysis method according to embodiments of the present invention will be described with reference to the drawings.
[0038]
In the present embodiment, a working electrode, a counter electrode, and a reference electrode are configured, and a solution (for example, tap water) containing an analysis target (metal ion such as lead) having an extremely low concentration (for example, a concentration of 1 nM to 100 nM level). In the voltammetric analyzer for analyzing the above), an electrode that has hardly been tried before, that is, an electrode made of copper (hereinafter referred to as a copper electrode) is applied as the working electrode. The electrodeposition of the object to be analyzed on the copper electrode is a state in which a solution degassing step is performed as necessary, and mass transfer in the solution is promoted by mass transfer promoting means (hereinafter referred to as a mass transfer promoting atmosphere). ) And the potential of the copper electrode is set to a desired negative potential (for example, about −1.2 to −0.5 V with respect to the Ag / AgCl reference electrode).
[0039]
Thereafter, the potential of the copper electrode is swept in the positive potential direction from the negative potential at a desired sweep rate (for example, about 1 mV / s to 100 mV / s with respect to the Ag / AgCl reference electrode). The electrodeposition substance is eluted by sweeping to a potential), and a current change with respect to the potential change of the copper electrode is detected, and an electric quantity obtained by integrating the current change is compared with a calibration curve ( Alternatively, the peak value of the object to be analyzed is read as in the fifteenth example described later), and the object to be analyzed is analyzed.
[0040]
The potential of the copper electrode is swept until it reaches a positive potential (for example, about 0 to 150 mV with respect to the Ag / AgCl reference electrode), and at that potential for a predetermined time (for example, 0 to 0 with respect to the Ag / AgCl reference electrode). 30 seconds), the copper electrode surface is eluted at the molecular level and a regeneration (regeneration that does not require grinding, polishing, cleaning, etc.) is performed.
[0041]
In addition, before performing analysis with a solution analyzer as described above (for example, before performing analysis with an analyzer that has not been used for a predetermined period of time), a positive potential (for example, Ag / The regeneration step may be performed by applying a voltage of about 100 to 200 mV to the AgCl reference electrode and holding it for a predetermined time (for example, 5 to 30 seconds). Furthermore, after sweeping the copper electrode in the positive potential direction to 0 V to complete the analysis, a positive potential of a predetermined magnitude with respect to the copper electrode (for example, 100 to 500 mV with respect to the Ag / AgCl reference electrode). The above regeneration step may be performed by applying a predetermined time (for example, 5 to 30 seconds).
[0042]
[Example]
Next, an analysis apparatus (manufactured by Hokuto Denko) as shown in a schematic explanatory diagram of FIG. 1 using a copper electrode as a working electrode (the same reference numerals are used for the same components as those in FIGS. 24 and 25 and the detailed description is omitted). And a solution containing various metal ions according to first to eighteenth embodiments shown below (solution assuming clean water), and a potentiostat (electrochemical measurement system-HZ3000) or the like. And actual tap water).
[0043]
In the analyzer shown in FIG. 1, a 1.6 mm diameter copper electrode was used for the working electrode 2, a spiral platinum electrode was used for the counter electrode 3, and an Ag / AgCl electrode was used for the reference electrode 5. HNO _Three A 0.2 M KCl solution containing 0 to 200 nM lead ions and adjusted to pH 3 with N ₂ A sample solution 1a is obtained by degassing with gas for 15 minutes, and this sample solution 1a is analyzed in the same manner as in the first embodiment to be described later (electrodeposition sets the potential of the working electrode 2 to the reference electrode 5 to -550 mV). 10 minutes) to obtain a calibration curve (electrical quantity characteristics with respect to the lead ion concentration). As shown in FIG. 2, the calibration curve has good linearity, and the analyte to be analyzed is very low in concentration. It was confirmed that analysis was possible with high accuracy and high sensitivity.
[0044]
(First embodiment)
First, HNO _Three A 0.2 M KCl solution containing 50 nM lead ions adjusted to pH 3 was obtained. Immediately before the analysis, the 0.2 M KCl solution is added with Na. ₂ SO _Three (In this example, Na was added at a rate of 10 ml per 1 l of 0.2M KCl solution. ₂ SO _Three ) Is added to the sample liquid 1 (20 ml sample liquid in this embodiment) 1a in the container 1 of FIG. 1 (30 ml container in this embodiment), and the sample liquid 1a It sealed with the sealing member 1b so that the working electrode 2, the counter electrode 3, and the reference electrode 5 might be immersed. Thereafter, the working electrode 2 of the lead ions in the sample solution 1a is set by setting the potential of the working electrode 2 with respect to the reference electrode 5 to -700 mV while maintaining a mass transfer promoting atmosphere through the stirrer 7 and the stirring bar 7a. Electrodeposition on the surface was performed for 1 to 15 minutes.
[0045]
Then, the stirrer 7 and the stirrer 7a are stopped, and the potential of the working electrode 2 with respect to the reference electrode 5 is swept from -700 mV to the positive potential direction at a sweep speed of 25 mV / s, whereby electrodeposition of the surface of the working electrode 2 is performed. The substance was oxidized and eluted (anode stripping) into the sample solution 1a, and the current change with respect to the potential change of the working electrode 2 was detected. The detection result is shown in the current change characteristic diagram with respect to the potential change in FIG.
[0046]
From the characteristic curve shown in FIG. 3, the amount of electricity in the region where the peak current was generated by the lead ions was calculated and compared with the calibration curve in FIG. 2. As a result, the sample solution 1a contained 50 nM lead ions. It could be confirmed.
[0047]
Further, after sweeping the working electrode 2 in the positive potential direction up to 150 mV, the state of the surface of the working electrode 2 was observed, and it was confirmed that there was no residue and the like was in a mirror state. This is because, as described above, the potential of the working electrode 2 is swept to a positive potential, so that the surface of the working electrode 2 is eluted and regenerated at the molecular level (that is, the surface of the working electrode 2 is smoothed, adhered matter, etc. It is conceivable that
[0048]
Further, the potential of the working electrode 2 when electrodepositing lead ions in the sample solution 1a was set to -500 mV or -1.2 V, and the current change characteristics with respect to the potential change similar to FIG. It was possible to analyze in the same manner as when the potential of 2 was set to -700 mV, and it was confirmed that the working electrode 2 was regenerated.
[0049]
(Second embodiment)
10 μM copper ions (Cu ²⁺ ) To obtain a new sample solution 1a, and the sample solution 1a is subjected to the same analysis work as in the first embodiment, thereby detecting a current change with respect to a potential change of the working electrode 2 and detecting the result. Is shown in the current change characteristic diagram with respect to the potential change in FIG.
[0050]
From the characteristic curve shown in FIG. 4, each peak current of lead ions and copper ions (peak current due to copper ions is not shown) is detected at different potentials, and each metal ion interferes with each other (for example, formation of an alloy). It was confirmed that analysis was possible without any problems.
[0051]
In addition, when the amount of electricity in the region where the peak current was generated by the lead ions was calculated and compared with the calibration curve of FIG. 2, the sample solution 1a contained 50 nM lead ions as well as the first example, and the working electrode 2 It was confirmed that the surface was regenerated.
[0052]
Furthermore, when the potential of the working electrode 2 when electrodepositing each metal ion in the sample solution 1a was set to -500 mV or -1.2 V, the current change characteristics with respect to the potential change similar to FIG. Analysis was possible in the same manner as when the potential of the electrode 2 was set to -700 mV, and it was confirmed that the working electrode 2 was regenerated.
[0053]
(Third embodiment)
In the sample solution of the second embodiment, 100 nM cadmium ions (Cd ²⁺ ), 5 μM iron ion (Fe ²⁺ ) To obtain a new sample solution 1a, and the sample solution 1a is subjected to the same analysis work as in the first embodiment, thereby detecting a current change with respect to a potential change of the working electrode 2 and detecting the result. Is shown in the current change characteristic diagram with respect to the potential change in FIG.
[0054]
From the characteristic curves shown in FIG. 5, the peak currents of lead ions, copper ions, cadmium ions, and iron ions (peak currents due to copper ions and iron ions are not shown) are detected at different potentials. It was confirmed that analysis was possible without interference.
[0055]
In addition, when the amount of electricity in the region where the peak current was generated by the lead ions was calculated and compared with the calibration curve of FIG. 2, the sample solution 1a contained 50 nM lead ions as well as the first example, and the working electrode 2 It was confirmed that the surface was regenerated.
[0056]
Furthermore, the potential of the working electrode 2 when electrodepositing each metal ion in the sample solution 1a was set to −1.2 V, and the current change characteristics with respect to the potential change similar to FIG. Analysis was possible in the same manner as when the potential was set to -700 mV, and it was confirmed that the working electrode 2 was regenerated. Furthermore, when the potential of the working electrode 2 at the time of electrodeposition was set to -500 mV, the same result as that obtained when the potential of the working electrode 2 was set to -700 mV was obtained. Since the potential of 2 was nobler than the electrodeposition potential of cadmium, no detection of cadmium was made.
[0057]
(Fourth embodiment)
In the sample solution of the third embodiment, 10 μM zinc ions (Zn ²⁺ ) To obtain a new sample solution 1a, the potential of the working electrode 2 when electrodepositing each metal ion in the sample solution 1a is set to -1.2 V, and the first solution for the sample solution 1a By performing the same analysis work as in the example, the current change with respect to the potential change of the working electrode 2 was detected, and the detection result is shown in the current change characteristic diagram with respect to the potential change in FIG.
[0058]
It can be read from the characteristic curves shown in FIG. 6 that the peak currents of lead ions, cadmium ions, and zinc ions (peak currents due to copper ions and iron ions are not shown) are detected at substantially the same potential. This is probably because the metal ions interfered with each other when the electrodeposition material of the working electrode 2 was eluted. However, it was confirmed that separation and detection were possible when the zinc ion concentration was 1 μM or less.
[0059]
Therefore, the potential of the working electrode 2 when electrodepositing each metal ion in the sample solution 1a is set to −700 mV, and the sample solution 1a is subjected to the same analysis work as in the first embodiment, thereby The current change with respect to the potential change of the electrode 2 was detected, and the detection result is shown in the current change characteristic diagram with respect to the potential change in FIG.
[0060]
From the characteristic curves shown in FIG. 7, the peak currents of lead ions, copper ions, cadmium ions, iron ions, and zinc ions (peak currents due to copper ions, iron ions, and zinc ions are not shown) are detected at different potentials. I can read that. That is, it was confirmed that the metal ions can be analyzed without interfering with each other by variously setting the potential at the time of electrodepositing the analyte to the working electrode according to the analyte.
[0061]
In addition, when the amount of electricity in the region where the peak current was generated by the lead ions was calculated and compared with the calibration curve of FIG. 2, the sample solution 1a contained 50 nM lead ions as well as the first example, and the working electrode 2 It was confirmed that the surface was regenerated. Further, the potential of the working electrode 2 when electrodepositing each metal ion in the sample solution 1a was set to −500 mV, and the current change characteristics with respect to the potential change similar to FIG. It was confirmed that the same result as that obtained when the voltage was set to −700 mV was obtained.
[0062]
(5th Example)
In general tap water, chlorine (for example, about 1 ppm of chlorine) is mixed for the purpose of sterilization of the tap water. Therefore, in the fifth embodiment, the influence of solution analysis due to the presence or absence of residual chlorine in the solution was examined.
[0063]
First, HNO _Three A 0.1 M KCl solution containing 50 nM lead ions adjusted to pH 3 with N ₂ A new sample solution 1a was obtained by degassing with gas for 15 minutes. Then, by performing the same analysis work as in the first embodiment, the current change with respect to the potential change of the working electrode 2 was detected, and the detection result is shown in the current change characteristic diagram with respect to the potential change in FIG. From the characteristic curve shown in FIG. 8, the amount of electricity in the region where the peak current was generated by the lead ions was calculated to be 108 μC.
[0064]
Next, sodium hypochlorite is added to the sample solution used in the analysis of FIG. 8 so that the concentration in the sample solution becomes 1 ppm, and a new sample solution 1a is obtained. By performing the same analysis work as in the first embodiment, the current change with respect to the potential change of the working electrode 2 was detected, and the detection result is shown in the current change characteristic diagram with respect to the potential change in FIG. From the characteristic curve shown in FIG. 9, the amount of electricity in the region where the peak current was generated by lead ions was calculated to be 48 μC. From this, in the analyzer as shown in FIG. 1, when residual chlorine was mixed in the sample solution, it was confirmed that the current change with respect to the potential change at the time of oxidation elution is affected by the residual chlorine. .
[0065]
Here, ascorbic acid is added to the sample solution used in the analysis of FIG. 9 so that the concentration in the sample solution becomes 200 μM, and a new sample solution 1a is obtained. By performing the same analysis work as in the example, the current change with respect to the potential change of the working electrode 2 was detected, and the detection result is shown in the current change characteristic diagram with respect to the potential change in FIG. From the characteristic curve shown in FIG. 10, the amount of electricity in the region where the peak current was generated by the lead ions was calculated to be 105 μC (that is, the same as the result of FIG. 8).
[0066]
Therefore, in the analyzer configured as shown in FIG. 1, by adding ascorbic acid to the solution containing the analyte, even if residual chlorine is mixed in the solution, the residual chlorine It was confirmed that the analysis target could be analyzed without being affected.
[0067]
In addition to the method of using ascorbic acid to avoid the influence of solution analysis due to residual chlorine in the solution as described above, for example, a solution having residual chlorine is left in the atmosphere for a predetermined time, and the chlorine in the solution is removed. It was confirmed that there was a method of releasing into the atmosphere (for example, the sample liquid 1a used in the sixth and seventh examples was left in the atmosphere for a predetermined time to remove chlorine).
[0068]
(Sixth embodiment)
Using tap water in a lead pipe that was stopped for 3 hours (tap water containing lead ions eluted from the lead pipe), add 0.2 MKCl solution to the tap water, and adjust the pH to 3 to obtain a new sample solution. 1a was obtained, and the sample solution 1a was subjected to the same analysis work as in the first embodiment, whereby a change in current with respect to a change in potential of the working electrode 2 was detected.
[0069]
From the current change characteristic (not shown) with respect to the potential change of the detection result, each metal ion contained in the sample 1a was detected at a different potential. Further, when the amount of electricity in the region where the peak current was generated by the lead ions was calculated and compared with the calibration curve of FIG. 2, it was found that the sample solution 1a contained 48 nM lead ions. Therefore, it was confirmed that even when the object to be analyzed is tap water, each metal ion in the tap water can be analyzed without interfering with each other.
[0070]
Further, after sweeping the working electrode 2 in the positive potential direction up to 150 mV, the state of the surface of the working electrode 2 was observed, and it was confirmed that there was no residue and the like was in a mirror state.
[0071]
Further, the potential of the working electrode 2 when electrodepositing lead ions in the sample solution 1a was set to -500 mV or -1.2 V, and the current change characteristics with respect to the potential change similar to FIG. It was confirmed that the working electrode 2 could be regenerated as well as being analyzed in the same manner as when the potential of 2 was set to -700 mV.
[0072]
(Seventh embodiment)
By adding a lead solution containing 100 nM lead ions to the sample solution of the sixth embodiment to obtain a new sample solution 1a, and performing the same analysis work as that of the first embodiment on the sample solution 1a, A change in current with respect to a change in potential of the working electrode 2 was detected.
[0073]
From the current change characteristic (not shown) with respect to the potential change of the detection result, each metal ion contained in the sample 1a was detected at a different potential. In addition, when the amount of electricity in the region where the peak current was generated by the lead ions was calculated and compared with the calibration curve of FIG. 2, it was found that the sample solution 1a contained 148 nM lead ions. That is, it was found that the tap water used in the sixth example contained 48 nM lead ions. Therefore, even if the object to be analyzed is various mixed solutions (for example, a mixed solution of tap water and lead solution), it was confirmed that each metal ion in the mixed solution can be analyzed without interfering with each other.
[0074]
Further, after sweeping the working electrode 2 in the positive potential direction up to 150 mV, the state of the surface of the working electrode 2 was observed, and it was confirmed that there was no residue and the like was in a mirror state.
[0075]
Further, the potential of the working electrode 2 when electrodepositing lead ions in the sample solution 1a was set to -500 mV or -1.2 V, and the current change characteristics with respect to the potential change similar to FIG. It was confirmed that the working electrode 2 could be regenerated as well as being analyzed in the same manner as when the potential of 2 was set to -700 mV.
[0076]
(Eighth embodiment)
In general voltammetry, HNO is used as a solution for adjusting the pH of a sample solution (adjustment for keeping it constant under acidic conditions) (hereinafter referred to as a pH adjusting solution). _Three Or HCl is used. But HNO _Three Since solutions such as HCl and HCl have physical properties, they must be handled in consideration of safety. For example, an analyzer configured as shown in FIG. When analyzing metal ions in tap water, it becomes difficult to always keep the pH value of the sample solution constant due to a decrease in workability, leading to a decrease in analysis accuracy.
[0077]
Therefore, in the eighth example, an attempt was made to use a safe and easy-to-handle acetate buffer solution as the pH adjusting solution. First, a 0.1 M acetate buffer solution adjusted to pH 4.5 is added to tap water collected in Atsugi City, Kanagawa Prefecture so as to be 0 to 50 mM, and the acetate buffer solution in the tap water is added. The change in pH with respect to the concentration was examined. As a result, as shown in the characteristic diagram of FIG. 11, it can be read that the pH of tap water to which the acetate buffer solution is added so as to be about 10 mM or more becomes constant (pH 4.5).
[0078]
That is, by using an acetic acid buffer solution of about 10 mM or more as a pH adjusting solution, the analyzer as shown in FIG. _Three It was confirmed that good workability and analytical accuracy were maintained as compared with the case of using HCl or HCl.
[0079]
(Ninth embodiment)
To a 50 nM lead ion-containing aqueous solution adjusted to pH 4.5 with 10 mM acetate buffer solution, 0 to 200 mM KCl solution was added as a supporting electrolyte, and N ₂ Degassing treatment was performed with gas for 15 minutes to obtain various new sample solutions 1a. In the same manner as in the first embodiment, each of the sample solutions 1a is placed in the container 1, and the working electrode (diameter 1.6 mm (electrode area 0.02 cm) is placed in the sample solution 1a. ² )) 2, counter electrode 3 and reference electrode 5 are immersed and sealed, and the potential of working electrode 2 with respect to reference electrode 5 is set to −550 mV while maintaining a mass transfer promoting atmosphere by stirrer 7 and stirrer 7a. Electrodeposition of lead ions in each sample solution 1a on the surface of the working electrode 2 was performed for 3 minutes.
[0080]
Thereafter (after the stirrer 7 and the stirrer 7a are stopped), the potential of the working electrode 2 with respect to the reference electrode 5 is swept from -550 mV to 0 V at a sweep speed of 25 mV / s, whereby the electrodeposition material on the surface of the working electrode 2 Was oxidized and eluted in each sample solution 1a, and the current change with respect to the potential change of the working electrode 2 was detected. In each current change, the electric quantity in the region where the peak current was generated by the lead ions was calculated, and the calculation result is shown in the electric quantity characteristic diagram with respect to the concentration of the KCl solution in FIG. In the ninth embodiment, the target value of electricity is set to 50 × 10 ^-9 Set to C or higher.
[0081]
From the characteristic curve shown in FIG. 12, a sufficient amount of electricity (50 × 10 10) is obtained when the concentration of the KCl solution is in the range of about 3 to 100 mM. ^-9 C or more) is obtained, and it can be read that a good electric charge was obtained particularly when the concentration of the KCl solution was in the range of about 10 to 50 mM.
[0082]
That is, by adding a predetermined amount (for example, about 10 to 50 mM) of KCl as a supporting electrolyte to a sample solution whose pH is adjusted with an acetate buffer solution, a sufficient amount of electricity can be obtained in the analyzer configured as shown in FIG. The amount was obtained, and it was confirmed that the analysis could be performed with high sensitivity even if the analyte was at a low concentration.
[0083]
(Tenth embodiment)
In the case of using the sample solution 1a to which the 40 mM KCl solution is added in the ninth embodiment, the potential of the working electrode 2 with respect to the reference electrode 5 is held in the range of 0 to 450 mV for 10 seconds to thereby surface the working electrode 2. Each time regeneration is performed at each potential (hereinafter referred to as regeneration potential), the sample liquid 1a is analyzed in the same manner as in the ninth embodiment to detect a change in current with respect to a change in potential of the working electrode 2. The amount of electricity was calculated respectively. The calculation result is shown in the electric quantity characteristic diagram with respect to the reproduction potential in FIG. 13, and it was confirmed that the electric quantity increased as the reproduction potential increased.
[0084]
Therefore, the lead solution is added to the mixed solution of 10 mM acetate buffer solution (pH 4.5) and 40 mM KCl solution so that the lead ion concentration becomes 100 nM (degassing as in the ninth embodiment). Process) to obtain a new sample solution 1a, and the sample solution 1a is repeatedly subjected to the same analysis work as that of the ninth embodiment, and each electric quantity is calculated by detecting a current change with respect to a potential change of the working electrode 2 respectively. At the same time, the surface of the working electrode 2 was regenerated by holding the potential of the working electrode 2 with respect to the reference electrode 5 at 400 mV or 300 mV for 10 seconds for each analysis operation. The respective results are shown in the electric characteristic chart with respect to the number of analysis operations (that is, the number of regenerations) in FIGS.
[0085]
As shown in the characteristic curve of FIG. 14, when reproduction is performed at a reproduction potential of 400 mV, it can be read that the amount of electricity sequentially increases each time analysis is performed, and the reproducibility of analysis is low. The reason for this may be that the surface of the working electrode 2 is activated and the surface condition increases (the electrode area increases) for each regeneration.
[0086]
On the other hand, as shown in the characteristic curve of FIG. 15, it can be read that when reproduction is performed at a reproduction potential of 300 mV, the amount of electricity does not increase even if the analysis operation is repeated, and the reproducibility of the analysis is maintained.
[0087]
That is, by adjusting the regeneration potential (for example, within a range of about 0 to 300 mV), the surface of the working electrode 2 can be activated and the surface roughness can be increased even if the analysis operation and the regeneration process are repeated. It was confirmed that the increase could be prevented, a sufficiently good amount of electricity was obtained, and the reproducibility of the analysis could be maintained.
[0088]
(Eleventh embodiment)
A lead solution is added to a 40 mM KCl solution so that the lead ion concentration is 50 nM, and a 10 mM acetate buffer solution is further added so that the pH is 3.75 to 5.0 (as in the ninth embodiment). Various sample solutions 1a were newly obtained by degassing. For each of these sample solutions 1a, the same analysis work as in the ninth embodiment is performed to detect each current change with respect to the potential change of the working electrode 2 to calculate each electric quantity, and the result is calculated with respect to the pH of the sample solution in FIG. It is shown in an electric quantity characteristic diagram (a diagram in the case of a lead ion concentration of 50 nM). The working electrode 2 was regenerated by setting the regenerating potential to 300 mV.
[0089]
From the characteristic curve shown in FIG. 16, it can be read that the amount of electricity decreases when the acetate buffer solution is used so that the pH of the sample solution 1a exceeds about 4.75. On the other hand, it can be read that the amount of electricity can be made constant when the acetate buffer solution is used so that the pH is about 4.75 or less.
[0090]
That is, by using an acetate buffer solution so that the pH of the sample solution is about 4.75 or less (for example, using 10 mM or more of an acetate buffer solution having a pH of 4.75 or less), a sufficiently good amount of electricity can be obtained. It could be confirmed.
[0091]
(Twelfth embodiment)
A 40 mM KCl solution adjusted to a pH of 4.5 with a 10 mM acetate buffer solution is deaerated by adding a lead solution so that the lead ion concentration is 0 to 200 nM (as in the ninth example). Thus, various sample solutions 1a were newly obtained. Then, for each of the sample solutions 1a, the same analytical work as in the ninth embodiment is performed to detect a current change with respect to a potential change of the working electrode 2 and calculate an electric quantity from each of the detection results. (Electric quantity characteristics with respect to lead ion concentration) was determined. The working electrode 2 was regenerated by setting the regenerating potential to 300 mV.
[0092]
As shown in FIG. 17, it can be read that the calibration curve has good linearity, and it can be confirmed that analysis can be performed with high accuracy and high sensitivity even if the analyte is at a low concentration.
[0093]
(Thirteenth embodiment)
A 10 mM acetate buffer solution and 40 mM KCl solution are added to tap water collected in Atsugi City, Kanagawa Prefecture, and ascorbic acid is added in the same manner as in the fifth embodiment, followed by deaeration treatment (the ninth embodiment). A new sample solution 1a is obtained by degassing in the same manner as in Example 9. The sample solution 1a is analyzed in the same manner as in the ninth embodiment, and the current change with respect to the potential change of the working electrode 2 is detected. It was confirmed that the liquid 1a did not contain lead ions.
[0094]
Therefore, a lead solution is added to the sample solution 1a so that the lead ion concentration is 0 to 200 nM, and the analysis work similar to that of the twelfth embodiment is performed to detect the current change with respect to the potential change of the working electrode 2. Further, by calculating each electric quantity, a calibration curve (electric quantity characteristic with respect to lead ion concentration) was obtained and shown in FIG.
[0095]
As shown in FIG. 18, it was read that a calibration curve having good linearity was obtained, and it was confirmed that even if the analysis target in tap water had a low concentration, it could be analyzed with high accuracy and high sensitivity.
[0096]
In addition, for tap water collected in Zama City, Kanagawa Prefecture and Hino City, Tokyo (tap water in iron pipes), the same analysis as in the case of using tap water in Atsugi City was conducted. It was confirmed that lead water was not contained in the tap water and a calibration curve having good linearity was obtained as shown in FIG.
[0097]
(14th embodiment)
Tap water (tap water containing lead ions eluted from the lead pipe) in a lead pipe (new lead pipe) stopped at various times is collected, and 10 mM acetate buffer solution (pH 4. 5) and a 40 mM KCl solution are added and ascorbic acid is added in the same manner as in the fifth embodiment, followed by deaeration treatment (deaeration treatment in the same manner as in the ninth embodiment). Got. Then, each sample solution 1a was analyzed for lead ion concentration by the same analysis work and ICP emission spectroscopic analysis as in the ninth example, and the respective analysis results are shown in the correlation characteristic diagram of FIG.
[0098]
From the results shown in FIG. 19, according to the same voltammetric analysis method as in the ninth embodiment, even if the analyte in the solution such as tap water has a low concentration, it is equivalent to the ICP emission spectroscopic analysis method. Number of relations R ² = 0.983) It was confirmed that it was possible to easily analyze with sensitivity and accuracy. Moreover, it was confirmed that the same results were obtained in the present invention other than the ninth embodiment.
[0099]
(15th embodiment)
For example, when the analyzer configured as shown in FIG. 1 is transported to the area to be analyzed and metal ions in tap water are analyzed at the site, the work process is simplified and the analyzer is downsized. Is preferred. Therefore, in the fifteenth embodiment, an analysis method in which the deaeration process is omitted was examined.
[0100]
First, a new sample solution 1a was obtained by adding a lead solution to a mixed solution of a 10 mM acetate buffer solution (pH 4.5) and a 40 mM KCl solution so that the lead ion concentration was 50 nM. Then, as in the first embodiment, the sample solution 1a is put in the container 1, and the working electrode 2, the counter electrode 3 and the reference electrode 5 are immersed in the sample solution 1a and sealed, and the stirrer 7 and the stirring bar 7a are used. The potential of the working electrode 2 with respect to the reference electrode 5 was set to −550 mV while maintaining a mass transfer promoting atmosphere, and electrodeposition of lead ions in each sample solution 1a onto the surface of the working electrode 2 was performed for 3 minutes.
[0101]
Thereafter (after the stirrer 7 and the stirrer 7a are stopped), a sweep speed of 20 mV / s, a pulse height (pulse amplitude) of 50 mV, and a pulse width of 15 ms are determined by a differential pulse, anode stripping and voltammetry analysis method (hereinafter referred to as DPASV). , By sweeping from -550 mV to 0 V while stepping the potential of the working electrode 2 with respect to the reference electrode 5 at a pulse period of 100 ms, the electrodeposition substance on the surface of the working electrode 2 is oxidized and eluted into the sample liquid 1a, The current change with respect to the potential change of the working electrode 2 was detected, and the detection result is shown in the current change characteristic diagram with respect to the potential change in FIG.
[0102]
From the peak value (peak height) corresponding to the lead ion in the characteristic curve shown in FIG. 20, it can be read that 50 nM lead ion is contained in the sample solution. The reason why dissolved oxygen does not affect the analysis using DPASV is that the potential of the working electrode is swept in a potential step (pulse form) when the electrodeposited material is oxidized and eluted. This is because the current value due to oxidation elution can be detected before the dissolved oxygen starts the reaction.
[0103]
In the fifteenth embodiment, if the pulse wave height is greater than 0 mV and not greater than 50 mV, the pulse width is greater than 0 ms and not greater than 15 ms, and the pulse period is greater than 0 ms and not greater than 100 ms under the DPASV conditions, It was confirmed that analysis of the analyte in the solution was possible without processing.
[0104]
Accordingly, in the analyzer configured as shown in FIG. 1, by applying DPASV (DPASV in which pulse conditions are set so as not to be affected by the reaction of dissolved oxygen), the solution can be obtained without performing degassing treatment. It was confirmed that it was possible to analyze the object to be analyzed.
[0105]
(Sixteenth embodiment)
A lead solution is added to a mixed solution of a 10 mM acetate buffer solution (pH 4.5) and a 40 mM KCl solution so that the lead ion concentration is 0 to 100 nM to obtain a new sample solution 1a. The sample solution 1a The same analysis work as in the fifteenth embodiment is performed to detect current changes with respect to the potential change of the working electrode 2, and a calibration curve (peak value characteristic with respect to lead ion concentration) is obtained from the peak value due to lead ions of each current change. This is shown in FIG. The working electrode 2 was regenerated by setting the regenerating potential to 300 mV.
[0106]
As shown in FIG. 21, it can be read that a calibration curve having good linearity is obtained, and it is possible to analyze a low-concentration analyte in a solution with high accuracy and high sensitivity without performing a deaeration process. It could be confirmed.
[0107]
The same analysis as in the fifteenth example was conducted on tap water collected in Atsugi City, Kanama City, and Hino City, Tokyo. First confirmed that it did not contain lead ions. Therefore, 10 nM to 100 nM of lead was standardly added to these tap waters (and ascorbic acid was added in the same manner as in the fifth example), and the same analysis as in the fifteenth example was performed. As in FIG. It was confirmed that a calibration curve having good linearity was obtained.
[0108]
(Seventeenth embodiment)
In the general linear sweep voltammetry, when the electrode area of the working electrode is increased, a residual current is generated as the working electrode is increased, so that the analysis accuracy is not necessarily improved. Therefore, in the seventeenth embodiment, a new sample is first added by adding a lead solution to a mixed solution of 10 mM acetate buffer (pH 4.5) and 40 mM KCl solution so that the lead ion concentration becomes 100 nM. Liquid 1a was obtained. And about the said sample liquid 1a, the electrode area of the working electrode 2 is 0.02-0.2 cm by the analysis work similar to the said 15th Example. ² 22, while detecting a change in current with respect to a change in potential of each working electrode 2 while calculating the peak value due to lead ions of each current change, and calculating the peak value with respect to the electrode area in FIG. 22. It is shown in the value characteristic diagram.
[0109]
As shown in FIG. 22, it can be read that the electrode area of the working electrode 2 and the peak value have a proportional relationship. Therefore, by applying DPASV in the analyzer configured as shown in FIG. 1, the electrode area is increased and analysis sensitivity is improved without being affected by the residual current of the working electrode (ie, low concentration It was confirmed that the analysis target could be analyzed).
[0110]
(Eighteenth embodiment)
To the mixed solution of 10 mM acetate buffer solution (pH 4.5) and 40 mM KCl solution, lead solution is added so that the lead ion concentration is 5 nM to obtain a new sample solution (20 ml sample solution) 1a. The sample solution 1a is analyzed in the same manner as in the seventeenth embodiment to detect current changes with respect to potential changes of the working electrode 2, calculate peak values of these current changes due to lead ions, and calculate the results. The peak value characteristic diagram with respect to the electrode area in FIG. 23 is shown.
[0111]
From the results shown in FIG. 23, even if the analyte in the solution has a very low concentration, the electrode area of the working electrode 2 and the peak value have a proportional relationship, and the analysis sensitivity increases as the electrode area increases. I can read that. The electrode area is 0.02 cm. ² In the case where it is smaller than the above, deposits such as bubbles are observed on the surface of the working electrode 2 and it is confirmed that there is a tendency to influence the reproducibility of the analysis.
[0112]
Therefore, the electrode area is adjusted according to the concentration of the analyte (for example, 0.02 cm when analyzing 5 nM lead ions) ² By adjusting as described above, it was confirmed that the reproducibility of the analysis could be maintained and that a low concentration analyte in the solution could be analyzed with high accuracy and high sensitivity without performing deaeration treatment.
[0113]
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.
[0114]
For example, in the present embodiment, a sample solution containing an object to be analyzed is placed in a predetermined container, and analysis is performed while maintaining a mass transfer promotion atmosphere by a stirrer or the like. For example, the working electrode of the detector in the flow injection analyzer When a copper electrode is applied, since there is a mass transfer facilitating means (for example, a pump) for supplying a constant flow rate of sample liquid into the detector, the mass transfer facilitating atmosphere is not required without using the stirrer or the like. Can keep.
[0115]
In each example, a cylindrical working electrode is configured using copper. However, when a rotating electrode configured using copper is applied, a laminar flow is formed on the surface of the copper electrode by the rotation of the rotating electrode. Therefore, since the rotating electrode itself has a function of mass transfer promoting means, it is possible to maintain the mass transfer promoting atmosphere without using the stirrer or the like.
[0116]
Further, the electrode is composed of at least a working electrode, a counter electrode, a reference electrode, and a mass transfer accelerating means, and each of the electrodes is disposed in a solution containing the object to be analyzed, and the object to be analyzed is electrodeposited by the working electrode. If the solution analyzer is capable of detecting a change in current with respect to a change in potential while eluting into a solution, the working electrode for eluting the electrodeposited analyte into the solution as in the present embodiment is used. The working electrode can be regenerated by sweeping the potential to a positive potential or applying a positive potential to the working electrode before analysis.
[0117]
Furthermore, it is possible to perform more sufficient measurement by making the surface of the copper electrode into an active surface such as an uneven surface or a particle shape in advance.
[0118]
In addition, in each example, an Ag / AgCl electrode was used as a reference electrode of the analyzer configured as shown in FIG. 1. However, for example, a saturated calomel electrode was used instead of the Ag / AgCl electrode, and analysis conditions (for example, Even when the potential of the working electrode with respect to the reference electrode at the time of sweeping is set as appropriate, the same effects as those of the embodiments can be obtained.
[0119]
【The invention's effect】
As described above, according to the present invention, even when the concentration of the analyte in the solution is extremely low (for example, lead ions of 50 nM or less contained in clean water), for example, a mercury electrode is used without masking. As with the case of using, it is possible to easily analyze with high accuracy and high sensitivity, and it does not cause environmental pollution unlike the case of using a mercury electrode. In addition, since the surface of the working electrode elutes at the molecular level by adjusting the potential of the working electrode, the working electrode can be easily regenerated (without grinding, polishing, cleaning, etc.), and the reproducibility of the analysis is maintained. it can.
[0120]
Further, when the potential of the working electrode is swept in the positive potential direction, if the potential is stepped, it is not necessary to perform a deaeration process. Therefore, the work process can be simplified and the analyzer can be downsized. It becomes possible. Furthermore, it is possible to prevent the influence of the residual current and maintain the reproducibility of the analysis.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of a solution analyzer in the present embodiment.
FIG. 2 is a calibration curve for lead ions by the solution analyzer in the present example.
FIG. 3 is a current change characteristic diagram with respect to a potential change in the first embodiment.
FIG. 4 is a current change characteristic diagram with respect to a potential change in the second embodiment.
FIG. 5 is a current change characteristic diagram with respect to a potential change in the third embodiment.
FIG. 6 is a current change characteristic diagram with respect to potential change (electrodeposition potential of −1.2 V) in the fourth embodiment.
FIG. 7 is a current variation characteristic diagram with respect to potential variation in the fourth embodiment (electrodeposition potential −700 mV).
FIG. 8 is a current change characteristic diagram with respect to potential change in the fifth example (before adding sodium hypochlorite).
FIG. 9 is a current change characteristic diagram with respect to potential change in the fifth example (after adding sodium hypochlorite).
FIG. 10 is a characteristic diagram of current change with respect to potential change in Example 5 (after adding ascorbic acid).
FIG. 11 is a pH characteristic diagram of tap water with respect to the acetate buffer solution concentration in the eighth embodiment.
FIG. 12 is an electric quantity characteristic diagram with respect to the KCl solution concentration in the ninth embodiment.
FIG. 13 is an electric quantity characteristic diagram with respect to a reproduction potential in the tenth example (reproduction potential of 0 to 450 mV).
FIG. 14 is an electric quantity characteristic diagram (reproduction potential 400 mV) with respect to the number of analysis operations in the tenth embodiment.
FIG. 15 is an electric quantity characteristic diagram (reproduction potential: 300 mV) with respect to the number of analysis operations in the tenth embodiment.
FIG. 16 is an electric quantity characteristic diagram with respect to pH of the sample liquid 1a in the eleventh embodiment.
FIG. 17 is an electric quantity characteristic diagram with respect to lead ion concentration in the twelfth embodiment.
FIG. 18 is an electric quantity characteristic diagram with respect to lead ion concentration in the thirteenth embodiment.
FIG. 19 is a correlation characteristic diagram between a voltammetric analysis method (present invention) and an ICP emission spectroscopic analysis method in Example 14.
FIG. 20 is a current change characteristic diagram (DPASV) with respect to potential change in the fifteenth embodiment.
FIG. 21 is a peak value characteristic diagram with respect to the lead ion concentration in the sixteenth embodiment.
FIG. 22 is a peak value characteristic diagram with respect to the electrode area in the seventeenth embodiment.
FIG. 23 is a peak value characteristic diagram with respect to the electrode area in the eighteenth embodiment.
FIG. 24 is a schematic explanatory view showing an example of a voltammetric solution analyzer using a generally known solid electrode.
FIG. 25 is a schematic explanatory view showing an example of a solution analyzer by voltammetry using a generally known mercury electrode.
[Explanation of symbols]
1 ... Container
2 ... Working electrode
3 ... Counter electrode
4 ... Potentiostat
5. Reference electrode
6 ... Supply pipe
7 ... Stirrer

Claims (15)

It consists of at least a working electrode, a counter electrode, a reference electrode, and a mass transfer promoting means,
Each electrode is placed in a solution containing the analyte, and the current change relative to the potential change is detected while eluting the analyte electrodeposited by the working electrode into the solution. In a solution analyzer capable of analyzing an object to be analyzed,
The solution analyzer according to claim 1, wherein the working electrode is made of copper.   2. The solution analyzer according to claim 1, wherein the analyte to be analyzed is eluted by sweeping the potential of the working electrode in a positive potential direction while stepping the potential. 3. The solution analyzer according to claim 1, wherein an area of the working electrode is 0.02 cm ² or more. Placing a working electrode, a counter electrode, and a reference electrode in a solution containing the analyte;
Electrodepositing the analyte on the working electrode surface by setting the potential of the working electrode to a negative potential while maintaining a mass transfer promoting atmosphere;
Sweeping the potential of the working electrode in the positive potential direction and detecting the current change with respect to the potential change at the working electrode while eluting the electrodeposited analyte in the solution, and
A solution analysis method characterized in that an electrode made of copper is used as the working electrode, and an analyte to be analyzed at a level of 100 nM or less can be analyzed.   5. The solution analysis method according to claim 4, wherein the potential of the working electrode in the electrodeposition step is defined according to an analysis target contained in the solution.   6. The solution analysis method according to claim 4, wherein in the step of detecting the change in current, the potential of the working electrode is swept to a positive potential. The solution analysis method according to any one of claims 4 to 6, further comprising a step of degassing the solution before the electrodeposition step. Step, the potential of the working electrode solution analysis method according to any one of claims 4 to 6, characterized in that sweeping at a positive potential direction while the potential detecting the current change. Wherein the solution containing the analyte and the solution analysis method according to any one of claims 4 to 8, characterized in that the addition of acetate buffer solution 10mM or more. The solution analysis method according to any one of claims 4 to 9 , wherein the pH of the solution containing the analysis target is 4.75 or less. The KCl solution is added to the solution containing the analysis target so that the amount of electricity of the working electrode in the step of detecting the current change is 50 × 10 ⁻⁹ C or more. Item 11. The solution analysis method according to any one of Items 4 to 10. The solution analysis method according to any one of claims 4 to 11, wherein ascorbic acid is added to the solution containing the analyte. It is composed of at least a working electrode, a counter electrode, a reference electrode, and a mass transfer promoting means, and the working electrode is an electrode made of copper,
Each electrode of the arranged inclusive solution to be analyzed, to be analyzed, which is electrodeposited by the working electrode to detect the current change with respect to the potential changes eluting the solution, the following levels the 100nM In a method for regenerating a solution analyzer capable of analyzing an analysis target ,
A method for regenerating a solution analyzer, wherein the working electrode is regenerated by sweeping the potential of the working electrode when eluting the electrodeposited analyte into the solution to a positive potential.   14. The solution analysis according to claim 13, wherein the working electrode is regenerated by applying a positive potential to the working electrode at a constant potential and holding it for a predetermined time before performing the analysis by the solution analyzer. Device regeneration method.   The method for regenerating a solution analyzer according to claim 13 or 14, wherein the working electrode is regenerated by applying a positive potential of less than 400 mV to the working electrode.

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