JPS61126460A - Cell for coulometric analysis - Google Patents

Abstract

PURPOSE:To speed up analysis by packing a porous electrode of a liquid permeation type into an electrode chamber, specifying the bore of an inflow and outflow hole for a liquid contg. a material to be measured communicating with the inside and outside of the electrode chamber at <=5mm and electrolyzing the soln. to be measured in a static state after the supply of the soln. CONSTITUTION:The titled device is constituted of an electrolytic chamber 1 for the soln. to be measured, a counter electrode chamber 2 provided therefrom with a diaphragm 3 therebetween, the inflow and outflow holes 4A, 4B for the soln. to be measured, the inflow and outflow holes 5A, 5B for the counter electrode liquid and plates 6A, 6B for current collection, etc. The pipe bore of the holes 4A, 4B is set at <=5mm. The prescribed quantity of the soln. to be measured is supplied by a pump 8A into the chamber 1 in the stage of the measurement, then the pump 8A is stopped and while a counter electrode liquid pump 8B is kept operated, the electrolysis is executed with the stationary liquid by a constant potential method or constant current method. The quick automatic quantitative determination is thus made possible with the smaller amt. of the supply liquid and the time for one quantitative determination is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cell for coulometric analysis, and more particularly to a cell for coulometric analysis of a static solution type that can perform automatic quantitative determination quickly and easily.

(Prior Art) Coulometric analysis is one of the analytical methods that can serve as a primary standard along with gravimetric analysis, and it is theoretically possible to quantify extremely trace amounts of components with high precision. In other words, by determining the amount of electrolytic electricity of a substance to be quantified for which the number of electrons involved in oxidation or reduction is clear, standard materials such as standard solutions are prepared, similar to gravimetric analysis, which performs quantification by weighing the precipitated product. Accurate quantitative values can be obtained without the need for comparison.

In coulometric analysis, 1/100 coulomb to 1/1
It is possible to measure the amount of electricity of about 1,000 corons with extremely high precision, and when converted to the number of moles, this value is 10-7 to 1
This corresponds to a trace amount of 0-8 moles.

(Problems to be Solved by the Invention) However, even the coulometric analysis method, which is excellent in principle, has not been widely used in general due to the following problems.

(1) The substance to be quantified may not be easily electrolyzed;
Furthermore, even if it can be electrolyzed, the number of oxidation or reduction electrons may not be stable. In particular, when there is not just one type of electrolytic product but two or more types, multiple electrolytic reactions occur. The proportion contributing to the electrolytic reaction changes, and the number of oxidized or reduced electrons usually cannot be accurately determined, often resulting in extremely poor analytical accuracy.

(2) Similar to other electrochemical analysis methods such as portammetry, in trace analysis the signal-to-noise ratio (Si
gna]/Noise ratio (in this case, electrolytic current/residual current) becomes small, which has a large effect on analysis accuracy. When the residual current is stable at a constant value, it is relatively easy to correct the residual current value to improve analysis accuracy, but the problem is how to stabilize the residual current.

It is an object of the present invention to provide a coulometric analysis cell that eliminates the problems of the prior art described above, allows short electrolysis time, and allows quick and easy automatic quantitative determination.

(Means for Solving the Problems) The present inventor has filled an electrode chamber of a coulometric analysis cell with a liquid permeable porous electrode, and has an inlet and an outlet for a liquid containing a substance to be measured that communicates with the inside and outside of the electrode material. We have discovered that by electrolyzing a stationary solution to be measured by setting the inner diameter of the electrode to 51 mm or less, a small amount of solution can be electrolyzed almost linearly within the porous electrode, and the electrolysis time can be greatly shortened. This has led to the present invention.

That is, the present invention provides coulometric analysis in which a predetermined amount of a solution containing a substance to be measured is supplied into an electrode chamber, electrolysis is performed, and the quantity of electricity measured or a current value that decays over time is used to quantify the substance to be measured. In this cell, the electrode chamber is filled with a liquid-permeable porous electrode, and the inner diameter of the inlet and outlet holes for the liquid containing the analyte that communicate with the outside and outside of the electrode chamber is set to 5 mm or less, and after the solution is supplied, the cell is placed in a stationary state. It is characterized in that electrolysis is performed as follows.

In the present invention, if the electrode chamber is not filled with a porous chamber electrode, electrolysis cannot be carried out in a short time with high efficiency, and if the inner diameter of the solution flow hole exceeds 5n, the liquid will not diffuse into and out of the cell. (mixing) occurs, reducing analytical accuracy. Note that the length of the hole is desirably long to some extent; for example, when the inner diameter of the tube of the solution flow hole is 111, it is preferable to have a tube length of several n.

With the above configuration, the analysis time is shorter than the conventional electrolytic cell with a solution stirring type (H-type cell) or a device that uses a solution flow type electrolytic determination method even if a porous electrode is used. ,
Enables rapid measurement.

Furthermore, since the quantitative operation under the same conditions can be repeated in a short period, there is almost no fluctuation in the residual current during the -times of quantitative determination. Furthermore, due to the repeated analysis with high accuracy, the number of oxidized or reduced electrons is kept constant throughout the series of quantification, making extremely highly accurate quantitative analysis possible. Furthermore, even in the case of a substance to be quantified that has a low electrode reaction rate, stable quantification is possible in a short period of time.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 and FIG. 2 are explanatory diagrams of a coulometric analysis cell showing an embodiment of the present invention.

In FIG. 1, this device includes an electrolytic chamber 1 for a solution to be measured, a counter electrode chamber 2 provided with a diaphragm 3 between the electrolytic chamber 1, and a flow of the solution to be measured provided in the electrolytic chamber 1 and the counter electrode chamber 2, respectively. Human extraction holes 4A, 4B and counter electrode liquid flow human extraction holes 5A, 5B,
Current collecting plates 6A and 6B provided on the side surfaces of the electrolytic chamber 1 and counter electrode chamber 1, lead wires 7A and 7B connected to the current collecting plates, and wires covered with the electrolytic chamber 1 and counter electrode chamber 2, respectively. Liquid feeding pumps 8A and 8B and liquid feeding lines 9A and 9B for feeding the measurement solution and counter electrode liquid
It mainly consists of. The electrolytic chamber 1 is filled with a porous electrode IA, and the inner diameter of the test solution flow holes 4A and 4B of the electrolytic chamber 1 is set to 5 fi or less. During measurement, the pump 8A on the electrolytic chamber 1 side of the solution to be measured is operated to pump a predetermined amount of the solution to be measured into the electrolytic chamber 1.
After supplying the solution to the solution, the pump 8A is stopped, and the electrolytic amount is determined by pricking the solution into a stationary solution. Note that the counter electrode liquid is kept flowing by constantly operating the counter electrode pump 8B.

Figure 1 shows the electrolysis using the so-called two-electrode method, in which the counter electrode reaction is carried out at the same time, and the electrode potential is stabilized. , electrolysis may be performed using a three-electrode method using a reference electrode. The electrolysis method in the present invention is constant potential (constant voltage) or constant current coulometric analysis, and even if the electrolysis is not completely carried out, the current or voltage within a certain period of time in the initial stage of electrolysis is measured, and extrapolation is performed based on this. The total amount of the substance to be measured may be determined by the method.

FIG. 2 shows another embodiment of the present invention, in which the delivery of both electrode solutions to the electrolytic chamber 1 and the counter electrode chamber 2 of the solution to be measured is stopped during the analysis time. The liquid sending pump 8 may be common to both electrodes, which has the advantage of simplifying the device.

(Effects of the Invention) According to the present invention, the electrode chamber is filled with porous electrodes, the number of inflow and outflow holes for the electrode solution is set to 5 or less, and electrolysis is carried out in a static state. , enabling faster automatic quantification. Therefore, compared to conventional solution stirring type or /8 liquid circulation type enclosed analysis cells, the time required for quantification is shortened, the operation is extremely simple, and troubles such as breakdowns can be reduced. . Furthermore, compared to other analysis methods, such as optical analysis methods and analysis methods using electromagnetic waves, etc., the configuration of the detector, electric circuit, etc. is simpler, so it can be installed at a very low cost.

Hereinafter, specific examples of the present invention will be described.

(Example) Examples 1 to 3, Comparative Example 1.2 In the electrolytic cell shown in FIG. (Example 1), 3III+1 (Example 2), and 1-stroke (Example 3) vinyl chloride tubes were used to make four sets of electrolytic cells under the following conditions. In addition, a cell (comparative example 2) in which a polyvinyl chloride tube with an inner diameter of 1111 is used as the inflow and outflow hole for the solution to be measured, but in which the electrolytic chamber 1 is not filled with a porous electrode (carbon felt) is used. I made a prototype.

Measurement target / 8-liquid electrolyte chamber filled electrode IA: Carbon felt current collector plate) 7A, 7B: Phenol resin bound carbon plate (inside) Ten copper plate (outside) Diaphragm 3: Cation exchange membrane Weak phosphoric acid in the solution to be measured Acidic iodine, potassium iodine aqueous solution counter electrode: Same as the solution to be measured.

The structure of the counter electrode chamber side was the same as that of the electrolysis chamber side of the solution to be measured.

In the above apparatus, first, an iodine ion standard solution was sent to each of the test solution electrolysis chambers 1 of the five sets of cells, and its capacity was measured. Next, electrolytic determination of iodine and iodine ions in each solution to be measured was carried out using a constant potential method at ±0.4V. Separately, iodine and iodine ion concentrations in the solution to be measured were measured by thorium thiosulfate water titration method. The results are shown in Table 1.

Constant voltage electrolysis (constant potential) and constant current electrolysis were performed using the same standard solution and solution to be measured as in Table 1, Absolute 1, to determine the iodine and iodine ion concentrations in the solution to be measured. The results are shown in Table 2 and were fully satisfactory.

Table 2 Comparative Example 3 Iodine and iodine ions in the solutions to be measured in Examples 1 and 2 were determined using a conventional H-type cell with a platinum mesh electrode. The results are shown in Table 3.

Table 3 As is clear from Table 3, it can be seen that the conventional coulometric analysis takes a long time to measure, and the variation in the measured values is large.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are explanatory diagrams of a coulometric analysis cell showing an embodiment of the present invention. 1...Measurement solution electrolysis chamber, IA...Porous chamber electrode, 2
...Counter electrode chamber, 3...Diaphragm, 4A, 4B...Measurement solution outflow hole, 5A, 5B...Counter electrode outflow hole, 6A
, 6B...Current collecting plate, 7a, 7b...Lead wire, 8.8a, 8b...Liquid pump, 9a, 9b...
・Liquid delivery line. Agent Patent Attorney Takeshi Kawakita

Claims (2)

[Claims] (1) In a coulometric analysis cell in which a predetermined amount of a solution containing a analyte is supplied into an electrode chamber, electrolysis is performed, and the amount of electricity measured or a current value that decays over time is used to quantify the analyte. A liquid-permeable porous electrode is filled in the electrode chamber, and the inner diameter of the inlet and outlet holes for the liquid containing the substance to be measured that communicate into and outside the electrode chamber is 5 mm or less, and after the solution is supplied, electrolysis is performed in a static state. A cell for coulometric analysis characterized by being made to (2) The cell for coulometric analysis according to claim 1, wherein the electrolysis is performed by a constant current method or a constant potential method.