JP3234585B2 - Differential measurement of peracetic acid and hydrogen peroxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring peracetic acid using an electrochemical sensor and a method for separating peracetic acid from hydrogen peroxide. More specifically, without the need for additional reagents,
The present invention relates to a measurement method using an electrochemical sensor which enables instantaneous measurement of peracetic acid and separation measurement of peracetic acid and hydrogen peroxide.

[0002]

2. Description of the Related Art In the medical and food industries, peracetic acid is widely used as a bactericide. Peracetic acid has much better bactericidal activity than hydrogen peroxide, which has long been used as a bactericide. Furthermore, the burden on the material of the machine and the natural environment is much lower than that of sodium hypochlorite conventionally known as a disinfectant. In foreign countries, especially in the United States, peracetic acid is widely used as a disinfectant to replace sodium hypochlorite. In recent years, peracetic acid has been used as a bactericide in Japan, and its use has been increasing rapidly every year.

[0003] Peracetic acid for a fungicide is usually prepared by the following formula from hydrogen peroxide and acetic acid.

Embedded image Since it is synthesized by the reaction formula represented by the following formula, commercially available peracetic acid is a mixed aqueous solution of peracetic acid, hydrogen peroxide, acetic acid, and the like. It is important to control the concentration of peracetic acid in the form of such a mixed aqueous solution. The concentration of peracetic acid is measured by an iodine titration method (Japanese Patent Application Laid-Open No. 6-130051), a batch analysis method such as a spectroscopic method, or an electric conductivity method (Japanese Patent Application Laid-Open No.
503162, JP-A-6-7057, JP-A-9-127053, etc.). The batch-type analysis method requires an additional reagent, and it is difficult to measure the concentration instantaneously and continuously on the spot.
In addition, since the conventional electric conductivity method monitors the total electric conductivity of the mixed aqueous solution containing peracetic acid, the actual concentration of peracetic acid, hydrogen peroxide, etc. contained in the solution is measured separately. Can not do it. Therefore, the conventional analytical methods are not sufficiently satisfactory for accurately and accurately controlling the concentration of peracetic acid, hydrogen peroxide, and the like.

[0004]

Accordingly, it is an object of the present invention to measure the concentration of peracetic acid instantaneously and continuously using an electrochemical sensor and to measure the concentration of peracetic acid and hydrogen peroxide continuously. Another object of the present invention is to provide a method for separately and separately measuring.

[0005]

Means for Solving the Problems The present inventor can measure the concentration of peracetic acid instantaneously and continuously using an electrochemical sensor, and can measure the concentration of peracetic acid and hydrogen peroxide continuously. For the purpose of finding a method that can simultaneously perform fractional measurement, the results of a cyclic voltammogram of an aqueous solution containing peracetic acid and hydrogen peroxide on a gold electrode were -250 mV and -750 mV (vs. Ag / Ag).
Cl), one irreversible wave appears attributable to the reduction reaction of peracetic acid and hydrogen peroxide, respectively, that is, the respective detection potentials that give the limiting current values due to the reduction reaction of peracetic acid and hydrogen peroxide, respectively. Is -250 mV and -7
Being present at around 50 mV (vs. Ag / AgCl), and their detection potentials being far apart;
Therefore, the concentration of peracetic acid in the sample can be measured instantaneously and continuously based on the relationship between the concentration at the detection potential and the current value, and the respective concentrations of peracetic acid and hydrogen peroxide can be separately measured instantaneously and continuously. It has been found that the present invention is possible.

That is, the present invention is a method for separately measuring peracetic acid and hydrogen peroxide in a sample containing peracetic acid and hydrogen peroxide using an electrochemical sensor. Each detection potential that gives the limiting current value by the reduction reaction is applied to the electrode in the sample,
The respective current values are measured, and from the obtained current values, the peracetic acid and hydrogen peroxide in the sample are determined based on the calibration curve of the concentration and the current value at the respective detection potentials of peracetic acid and hydrogen peroxide prepared in advance. This is a method for separately measuring peracetic acid and hydrogen peroxide by measuring the respective concentrations of Furthermore, the present invention is a method for measuring peracetic acid in a sample containing peracetic acid using an electrochemical sensor, wherein a detection potential that gives a limiting current value due to a reduction reaction of peracetic acid is applied to an electrode in the sample. To measure the concentration of peracetic acid in the sample from the obtained current value based on a previously prepared calibration curve of the concentration at the detection potential of peracetic acid and the current value. This is a method for measuring acetic acid. Further, the present invention provides a working electrode for measuring peracetic acid or a working electrode for measuring peracetic acid and a working electrode for measuring hydrogen peroxide, a reference electrode and an auxiliary electrode, and further records and displays a sample injector, a potentiostat, and a current. An electrochemical sensor for use in any of the above measurement methods, including a controller for performing the measurement.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in order to measure peracetic acid and hydrogen peroxide in a sample using an electrochemical sensor, a limiting current value due to each reduction reaction of peracetic acid and hydrogen peroxide is given. Each detection potential is applied to an electrode in the sample, and each current value is measured. Next, from the obtained current value, the sample was prepared based on a calibration curve of the concentration and the current value at the respective detection potentials of peracetic acid and hydrogen peroxide prepared in advance using various known concentrations of peracetic acid and hydrogen peroxide. Determine the respective concentrations of peracetic acid and hydrogen peroxide in the solution. To carry out the measurement of the present invention, a normal electrochemical flow cell provided with a reference electrode and an auxiliary electrode together with a working electrode for measuring peracetic acid or a working electrode for measuring peracetic acid and a working electrode for measuring hydrogen peroxide is used. Alternatively, when a microelectrode is used as the working electrode, the counter electrode can also serve as a reference electrode, so that measurement can be performed even with a two-electrode system. In order to measure the concentration of peracetic acid, when Ag / AgCl is used as a reference electrode for the working electrode for measuring peracetic acid, the detection potential of the reduction reaction of peracetic acid is -150 m.
A potential ranging from V to -300 mV is applied, and the current value is measured. When measuring hydrogen peroxide, similarly, when Ag / AgCl is used as a reference electrode, -700 m
A potential ranging from V to -950 mV is applied to the working electrode for measuring hydrogen peroxide. As described above, since the two detection potentials are far apart (about 700 mV), the present invention enables the separate measurement of peracetic acid and hydrogen peroxide. In these potential ranges, the reduction reaction of dissolved oxygen (O ₂ ) in the sample also occurs, so that the concentration measurement of peracetic acid and hydrogen peroxide may be affected. However, the concentration of peracetic acid and hydrogen peroxide contained in a general disinfectant is 1
500-3000ppm, 5000-15000ppm
Therefore, the current generated by dissolved oxygen is sufficiently negligible compared to the current generated by the electrode reaction between high concentrations of peracetic acid and hydrogen peroxide.

Although the electrode reaction mechanism of peracetic acid and hydrogen peroxide is not yet clear at this time, the peak potential of peracetic acid, that is, the detection potential is shifted by the change of the pH of the solution, and thus the peracetic acid and hydrogen peroxide are shifted. It can be seen that protons are involved in the electrode reaction. Therefore, in order to accurately measure the concentration of peracetic acid, it is important to keep the pH of the measurement sample solution constant. For measuring the concentration of peracetic acid by the electrode reaction as in the present invention, for example, an acetate buffer (CH
Most preferably, it is carried out in ₃ COOH / CH ₃ COONa, pH = 4.7). Of course, it is preferable to use the same acetate buffer for the differential measurement of a sample containing both peracetic acid and hydrogen peroxide.

In the present invention, a solid electrode made of gold (Au), platinum (Pt), carbon (C), titanium (Ti) or the like is used as a working electrode for measuring peracetic acid or a working electrode for measuring hydrogen peroxide. Is preferred. As a working electrode for measuring peracetic acid or a working electrode for measuring hydrogen peroxide,
A modified electrode obtained by chemically treating the surface of an electrode made of gold, platinum, carbon, titanium or the like can also be used. Ag / AgCl, Hg / Hg as a reference electrode (reference electrode)
_An electrode composed of ₂ Cl ₂ , Ag / Ag ⁺ or the like is preferable. As auxiliary electrodes, gold, platinum, carbon, titanium,
It is preferable to use a solid electrode made of stainless steel or the like.

[0010] As in the present invention, a reference electrode and an auxiliary electrode are provided together with a working electrode for measuring peracetic acid or a working electrode for measuring hydrogen peroxide, and when the electrode active species reacts on the surface of the electrode, the magnitude of the reaction current is increased. Is affected by both the speed of the charge transfer reaction and the rate of diffusion of the reactive species. When a potential is applied to the electrode, the concentration of the reactive species is sufficiently high on the electrode surface. The current obtained at that time is governed by the electrode reaction speed and the charge transfer speed. However, as the electrode reaction proceeds, the number of reactive species on the electrode surface continues to decrease. The current obtained at that time is governed by the speed at which the reactive species diffuses from the offshore to the electrode, that is, the diffusion speed. In other words, the generation of a concentration gradient on the electrode surface greatly affects the measurement of the concentration of peracetic acid or hydrogen peroxide. Therefore, it is desirable to eliminate such a concentration gradient on the electrode surface. As a method of eliminating the concentration gradient, a method of making the electrode area extremely small (for example,
There are a method using a micro electrode), a method in which a measurement liquid flows on the surface of the electrode (for example, a method using a channel flow electrode), and a method in which the electrode is rotated (for example, a method using a rotating electrode). In the present invention, it is preferable to adopt a method of making the electrode area extremely small, or a method of making the measurement liquid flow on the surface of the electrode.

In order to extremely reduce the electrode area, it is preferable to use a microelectrode as a working electrode for measuring peracetic acid or an electrode for measuring hydrogen peroxide. For example, if a disk electrode having a diameter φ of 50 μm or less is used as these working electrodes, the material diffusion becomes three-dimensional diffusion, so that the limiting current can be easily obtained. In particular, in the present invention, the diameter φ of the disc electrode is 2
When a 5 μm gold electrode is used as a working electrode for measuring peracetic acid or an electrode for measuring hydrogen peroxide, an S-shaped cyclic voltammogram is obtained, and the limiting current thereof is preferable because it shows a wide potential window. In order for the measurement liquid to flow on the surface of the electrode, it is preferable to use a channel flow electrode as a working electrode for measuring peracetic acid or an electrode for measuring hydrogen peroxide. Also when a channel flow electrode is used, the cyclic voltammogram shows an S-shape, which is preferable because a limiting current can be obtained. In the measurement method of the present invention, since a negative potential is always applied to the electrode during the measurement, the adsorption phenomenon of the solute in the sample solution on the electrode surface is extremely low, and the electrode is hardly deteriorated. However, in order to stabilize the measurement with higher accuracy, it is desirable that the electrode is periodically electropolished to activate the electrode.

In order to carry out the measuring method of the present invention, a reference electrode and an auxiliary electrode are provided together with a working electrode for measuring peracetic acid or a working electrode for measuring peracetic acid and a working electrode for measuring hydrogen peroxide. An electrochemical sensor including a stat and a controller for recording and displaying the current is used. The system configuration of the electrochemical sensor used in the present invention is as shown in FIG. In FIG. 6, a flow path 11 for sampling a sample from a preparation tank 10 and a flow path 12 through which a buffer for measurement flows are provided, and a sample injector 14 provided in the flow path 11 and a buffer 1
The two flow paths are joined by the buffer solution feed pump 15 provided in 2. The combined measurement liquid is applied to two working electrodes 26 (a working electrode for measuring peracetic acid) and 27 (a working electrode for measuring hydrogen peroxide).
, And then flow through an electrochemical flow cell provided with a reference electrode 28 and an auxiliary electrode 29, and are discarded from an outlet 17 of the cell. The potentiostat 18 controls the potential of the electrodes of the flow cell. The peracetic acid and hydrogen peroxide in the measurement solution react at the working electrodes 26 and 27, respectively, to generate a reaction current. The magnitude of the generated current varies depending on the concentrations of peracetic acid and hydrogen peroxide. The potentiostat 18 sends the current generated at these electrodes to a controller 19. Control device 19
Displays and records the received current, and controls the buffer solution feed pump 15, the sample injector 14, the undiluted solution feed pump 21, and the like. The peracetic acid concentration management system also includes a buffer solution supply bottle 13, a stock solution tank 20, a stock solution supply flow path 22, a working liquid supply flow path 24, a sterilization line 25, a work liquid return flow path 23, and the like.

[0013]

According to the measuring method of the present invention, the concentration of peracetic acid can be instantaneously and continuously measured using an electrochemical sensor, and the concentration of peracetic acid and hydrogen peroxide can be instantaneously and continuously measured. It can be measured separately. Furthermore, the measurement method of the present invention is a simple method that does not require an additional reagent. The measurement method of the present invention is effective, for example, for measuring and controlling the concentration of peracetic acid and hydrogen peroxide contained in a peracetic acid working liquid which is a disinfectant used in a sterilization process in a food production line in a medical hygiene department.

[0014]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 (1) Measurement of Cyclic Voltammogram An electrochemical sensor provided with a disc-shaped gold microelectrode having a diameter φ of 25 μm as a working electrode, Ag / AgCl as a reference electrode, and stainless steel as an auxiliary electrode was used. At room temperature in a buffer solution, a mixed solution containing 4.58 mol / l of peracetic acid and 1.58 mol / l of hydrogen peroxide was added to about 20 ml.
The cyclic voltammogram of the 0-fold diluted solution was measured. The obtained cyclic voltammogram is as shown in FIG. As is clear from FIG. 1, an S-shaped cyclic voltammogram was obtained. From FIG. 1,-
250 mV and -750 mV (vs. Ag / AgCl)
In the vicinity, one irreversible wave attributed to the reduction reaction of peracetic acid and hydrogen peroxide appears. 250mV and -750m
It turned out that it exists near V.

(2) Measurement of Peracetic Acid Concentration, Hydrogen Peroxide Concentration and Limit Current Value As shown in Tables 1 and 2, for each solution containing peracetic acid and hydrogen peroxide at various concentrations,
Using the same electrochemical sensor as in (1) above, a detection potential of -200 mV was applied for the peracetic acid solution and -900 mV for the aqueous hydrogen peroxide solution, and the limiting current values at various concentrations were measured. The obtained limit current values are shown in Tables 1 and 2. The hydrogen peracetate concentration and the peracetic acid concentration shown in Tables 1 and 2 were determined by a known method of cerium sulfate titration (Analytical Chemistry Handbook / Revised Third Edition, p. 446 (1981), edited by The Japan Society for Analytical Chemistry: (Maruzen). The results shown in Tables 1 and 2 are shown in FIGS. 2 and 3, respectively. As is clear from FIGS. 2 and 3, there is a good linear relationship between the concentration of the hydrogen peroxide solution and the limiting current value, and between the concentration of peracetic acid and the limiting current value. Therefore, these should be used as a calibration curve. Thus, it was found that the concentration of hydrogen peroxide and the concentration of peracetic acid in the sample can be accurately obtained based on the limit current value obtained by measuring the limit current value.

[0016]

[Table 1]

[0017]

[Table 2]

Example 2 A bactericide actually used on site is diluted with water, and 8 to 18% according to the actual concentration range of the germicidal working solution.
(W / w) in a series of peracetic acid solutions (1300-3000p
pm) and aqueous hydrogen peroxide solution (4500-10000p
pm). Table 3 shows the concentration obtained by the conventional measuring method (cerium sulfate titration method) and the response current value (that is, the limiting current value) obtained by the same measuring method as in Example 1.
And 4. FIG. 4 shows the correlation between the present invention and the conventional measurement method in which the respective values are plotted as shown in Tables 3 and 4.
And FIG. As is clear from FIGS. 4 and 5,
It can be seen that all of the results agree well with the results of the conventional measurement method.

[0019]

[Table 3]

[0020]

[Table 4]

[Brief description of the drawings]

FIG. 1 shows a cyclic voltammogram obtained in Example 1.

FIG. 2 is a graph showing a relationship between a hydrogen peroxide concentration and a limit current value.

FIG. 3 is a graph showing a relationship between a peracetic acid concentration and a limit current value.

FIG. 4 shows measured values of peracetic acid concentration according to a conventional method,
4 is a graph showing a relationship between a limiting current of a peracetic acid solution and a side constant value according to the method of the present invention.

FIG. 5 is a graph showing the relationship between the measured value of the hydrogen peroxide concentration according to the conventional method and the measured value of the limiting current of the hydrogen peroxide solution according to the method of the present invention.

FIG. 6 is a schematic diagram of a peracetic acid concentration management system according to the method of the present invention.

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 27/416 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A method for separately measuring peracetic acid and hydrogen peroxide in a sample containing peracetic acid and hydrogen peroxide using an electrochemical sensor, the method comprising limiting the respective reduction reactions of peracetic acid and hydrogen peroxide. Each detection potential that gives a current value is applied to the electrode in the sample, each current value is measured, and based on the obtained current value, the detection potential at each detection potential of peracetic acid and hydrogen peroxide prepared in advance is determined. A method for separately measuring peracetic acid and hydrogen peroxide, wherein the respective concentrations of peracetic acid and hydrogen peroxide in a sample are measured based on a calibration curve of the concentration and the current value. 2. The method according to claim 1, wherein the measurement is performed using an electrochemical sensor provided with a working electrode for measuring peracetic acid, a working electrode for measuring hydrogen peroxide, a reference electrode and an auxiliary electrode. 3. In the case where Ag / AgCl is used as a reference electrode, a potential in a range of -150 mV to -300 mV and a potential in a range of -700 mV to -950 mV as detection potentials of peracetic acid and hydrogen peroxide. Is applied to the electrodes in the sample, respectively. 4. A method for measuring peracetic acid in a sample containing peracetic acid using an electrochemical sensor, wherein a detection potential giving a limiting current value due to a reduction reaction of peracetic acid is determined with respect to an electrode in the sample. Apply, measure the current value, and measure the concentration of peracetic acid in the sample from the obtained current value based on the calibration curve between the concentration at the detection potential of peracetic acid and the current value prepared in advance. Measurement method. 5. A working electrode for measuring peracetic acid or a working electrode for measuring peracetic acid and a working electrode for measuring hydrogen peroxide, a reference electrode and an auxiliary electrode are provided, and a sample injector, a potentiostat, and a current are recorded and displayed. An electrochemical sensor for use in the measurement method of any of claims 1 to 4, comprising a controller for: