JPH01232248A - Method and apparatus for electrochemical analysis - Google Patents

Abstract

PURPOSE:To decrease the amt. of the sample required for an analysis by applying oscillation to a soln. to be measured to uniformize the soln. at the time of the analysis. CONSTITUTION:A sample vessel 12 contains the soln. 13 to be measured and the front end of an oxygen electrode 11 is immersed therein. The electrode 11 and a movable arm 14 are vertically oscillated by the fluctuation of the magnetic force of an excitation coil 17 around the position where the attraction from below by the coil 17 and the attraction from above by a spring 16 balance with each other in accordance with the frequency and power of the AC applied by an AC power supply 18 for excitation. The output current value of the oxygen satd. aq. soln. at 20 deg.C is maximized as shown in the figure (a) when the bias voltage Vb of a DC power supply 18 for biasing to be passed to the coil 17 is 10V and the frequency of an AC power supply 19 for excitation is 40Hz. This max. value is nearly the same as the value obtd. when the soln. is stirred by using a magnetic stirrer. The equal output level is, therefore, attained without using a stirrer.

Description

[Detailed Description of the Invention] [4 Required] Regarding a method and apparatus for electrochemically analyzing a substrate in a solution, a certain amount or more of a sample to be measured is required to mechanically stir the solution during analysis. However, with the aim of reducing this required amount, the structure is such that vibration is applied to the electrode means, sample solution container, etc. to homogenize the solution by vibration.

[Industrial application field]

The present invention relates to a method and apparatus for electrochemical analysis of minute amounts of solutions. Measuring specific substances in solutions is used in the chemical industry,
It is used in a wide range of fields, from basic research to the field, such as the food industry, brewing industry, and clinical testing. For example, oxygen concentration and glucose concentration in an aqueous solution are measured to manage and control substance concentrations during reaction processes in the chemical industry, and to analyze various substrates in specimens in clinical tests.

[Conventional technology]

Conventionally, when measuring a substrate in a solution as described above, the measurement electrode device is usually inserted into an appropriate amount of diluted solution, and the sample is added to the diluted solution while stirring the diluted solution. , the concentration of the original sample is calculated from the change in the output of the electrode.

In such measurements, stirring of the diluted solution is essential. That is, for example, in a so-called enzyme electrode that combines an oxygen electrode and an immobilized enzyme, the decreasing amount of oxygen is measured using the following formula: and this is made to correspond to the substrate (eg, glucose) concentration in the solution.

At this time, in order to know the amount of decrease in oxygen concentration, it is first necessary to know the oxygen concentration value before sample addition.

In an oxygen electrode, oxygen is reduced on the electrode surface,
The reduction current is output, but if the diluted solution using an oxygen electrode and the enzyme electrode inserted is stationary, the output of the electrode is controlled by the oxygen diffusion rate of the water near the electrode. The output current becomes a much smaller value than when stirring the liquid.

Furthermore, when measuring a specific substrate, the substrate is consumed by the immobilized enzyme, resulting in a decrease in output as in the case of oxygen, and the output becomes extremely unstable. In other words, irregular and slight fluctuations in the liquid near the electrode cause temporal fluctuations in the amount of substrate supplied to the immobilized enzyme.
This affects the output. For this reason,
It was essential to stir the diluted solution during measurements.

In order to stir the diluted liquid, generally a stirrer is inserted into the diluted liquid and stirred by magnetically rotating the stirrer.

[Problem to be solved by the invention]

However, in order to stir the liquid, a diluent volume of at least 1- or more is required, and when the dilution ratio is considered, there is a limit to how much the sample volume can be reduced. Therefore, when analyzing a specific sample, it is desirable to measure the sample without using a stirrer.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems and provide a method and apparatus for electrochemical analysis of a minute amount of solution, which reduces the amount of sample required for analysis.

[Means to solve the problem]

In the present invention, the solution to be measured is vibrated by some method as a means for accurately measuring the solution to be measured without using a magnetic stirrer. That is, the liquid has a frequency f (H
The frequency vibration of z) is set to a resonance frequency determined by the shape of the liquid capacity container and other conditions, and the liquid is vibrated, resulting in a forced stirring state in the liquid, and the components in the solution are made uniform.

That is, the gist of the present invention is a method for electrochemically analyzing a specific substrate in a solution using an electrode means, which is characterized in that the solution to be measured is homogenized by applying vibrations during the analysis. It is an electrochemical analysis method.

Similarly, another gist of the present invention is a container containing a solution to be measured, an electrode means for electrochemically analyzing a specific substrate in the solution to be measured by being immersed in the solution to be measured;
An electrochemical analysis apparatus characterized by comprising means for applying vibration to a solution to be measured in the container.

The frequency of vibration applied to the solution preferably matches the resonant frequency of the solution system, which is determined by the volume of the liquid, the shape of the container, etc., as described above. This is because at this time, the effect of homogenizing the solution (stirring force) is also maximized. In addition, it is preferable that the device is capable of adjusting the frequency of the vibration applied to the system together with the power so that vibration of such a resonant frequency can be applied arbitrarily to a specific solution system.

Vibrations can be applied to the solution by either vibrating the container containing the solution or by vibrating the electrode means immersed in the solution for analysis, with the aim of minimizing the sample volume. Although preferred, it is not excluded to insert special vibration applying means into the solution.

[For production]

In the present invention, the solution is homogenized by applying vibration to the solution. As a result, there is no need to use a conventional stirrer, and the required amount of sample solution can be reduced.

〔Example〕

FIG. 1(a) is a diagram showing the principle of the present invention when the electrode means side is vibrated, and FIG. 1(b) is the case where the sample container side is vibrated.

In these figures, 1 and 4 are electrode means, 2.5 is an excitation mechanism, and 3.6 is a sample container.

In this case, the output from the electrode means at the same concentration is a function of frequency, with the output reaching a maximum at the resonance point of the solution system. A schematic diagram showing this situation is shown in FIG. In FIG. 2, curve A represents the output value from the electrode means at a small amplitude and curve B at a large amplitude when the excitation frequency is varied. These curves show that the solution system resonates at a specific frequency and the agitation state (uniformity) of the solution reaches its maximum, and that the resonance frequency and maximum output value change depending on the amplitude of the vibration applied to the system. is recognized. In addition,
As mentioned above, the resonance frequency also changes depending on the amount of solution, container, etc.

FIG. 3 shows an apparatus according to an embodiment of the present invention. In the figure, 11 is an oxygen electrode with a diameter of 10 beads and a length of 50 m, and 12 is a sample container that contains a solution to be measured 13.
The tip of 1 is immersed. A movable arm 14 is attached to the upper part of the oxygen electrode 11, and the other end of the movable arm 14 is pivotally attached to a fixed frame 15 so that it can swing up and down. The movable arm 14 is pulled from above by a spring 16 whose other end is fixed to a fixed frame, and magnetically pulled from below by an excitation coil 17 with a DC resistance of 50 Ω and an inductance of 100 m). ing. The excitation coil 17 is biased with a bias DC power supply 18 and then excited with an excitation AC power supply 19 . Therefore, the oxygen electrode 11 and the movable arm 14 are connected to the bias DC power supply 1.
The magnetic force from the excitation coil changes based on the frequency and power of the alternating current applied by the excitation AC power source 19, centered on the position where the downward force of the excitation coil 17 and the upward force of the spring 16 are balanced. It vibrates up and down. The magnitude of the maximum output value in the resonant state shown in FIG. 2 can be selected by adjusting the bias voltage of the DC power supply 18, and the resonant frequency can be achieved by adjusting the frequency of the AC power supply 19. Note that the output detected by the oxygen electrode is sent to the recording device 2 via the power amplifier 20.
It is recorded as 1.

In FIG. 3, an example of a circuit for controlling the bias voltage of the DC power source 18 and the frequency and power of the AC power source 19 is shown in FIG. In FIG. 4, 31 is a low frequency oscillator, and the low frequency power generated by this is sent to the power amplifier 32.
At the same time, a bias voltage is applied by a DC constant voltage power supply 33 and the signal is supplied to an excitation coil 34 .

Example 1 Using the apparatus shown in FIGS. 3 and 4, the output current value of an oxygen-saturated aqueous solution at 20° C. was measured by changing the DC component and AC component flowing through the excitation coil. The excitation waveform is a sine wave, the excitation voltage is IOV (rms), and the sample volume is 50-
It is.

The results are shown in Figure 5. For comparison, FIG. 5 also shows the measurement level under stirring using a conventional magnetic stirrer.

From the same figure, bias voltage vb is 4V, 6V, 8V, IO
It can be seen that as the value of V is increased, the maximum output value gradually becomes higher. The output reaches a maximum at a DC voltage of 10 V and a frequency of 407, and this maximum value is almost the same as when the solution is stirred using a magnetic stirrer according to the conventional method.

Therefore, it was confirmed that according to the present invention, it is possible to achieve an output level equivalent to the conventional one without using a stirrer.

Example 2 Glucose (glucose) oxidase (05D) was immobilized on the sensitive part of the oxygen electrode shown in FIG. 3 to operate as a glucose sensor. First, C0D (manufactured by Toyobo, Aspergi
ns Niger origin) and 10 μg of bovine serum albumin were dissolved in 1 mg of water. A 50% aqueous solution of gluculaldehyde 20111 was added to this and mixed well.

This solution LOd was placed on the dialysis membrane 1. : Dropped dropwise and dried at 4°C for 1 day and night. This resulted in an insoluble, immobilized enzyme membrane that could be used as a reusable sensor. This membrane was attached to the tip of an oxygen electrode similar to that shown in FIG. 3, and the output to a glucose solution of known concentration was measured.

The obtained characteristics are shown in FIG. This characteristic is almost the same as that of a conventional sensor using magnetically forced stirring, and it was confirmed that measurement of a glucose sensor can also be performed using the method and apparatus of the present invention without using a stirrer. Further, according to the present method, the amount of solution required may be as low as about 0.5, making it possible to significantly reduce the amount of solution that was conventionally required to be 1 or more.

In this example, the required amount of solution was reduced to 1/2 of the conventional amount, but it can be further reduced by modifying the shape of the device.

〔Effect of the invention〕

According to the present invention, in electrochemical analysis of a minute solution sample, it is possible to reduce the minimum amount of sample solution required for measurement to 1/2 or less compared to the conventional magnetic stirring method. This method has the effect of making it easier to prepare or collect samples, and also making it possible to stably measure samples that have been difficult to measure in the past.

Furthermore, since there is no part other than the sample container that comes into contact with the sample,
This has a great effect on reducing cleaning operations, etc.

In addition, in the method of vibrating the electrode, adsorbed substances (contaminants) on the electrode surface are easily removed, which has a cleaning effect and is effective in extending the life of the electrode.

[Brief explanation of the drawing]

Figures 1 (A) and (B) are principle diagrams of typical embodiments of the present invention; Figure 2 is a schematic diagram explaining the characteristics of the embodiment; Figure 3 is a schematic diagram of the analytical device of the embodiment; Figure 4 is a schematic diagram of the power supply section of the example, Figure 5 is a graph of the output current with respect to excitation frequency showing the results of the example in which oxygen concentration was measured using the device in Figure 3, and Figure 6 is another example. FIG. 2 is a graph diagram showing measurement results by the glucose sensor of FIG. 1.4... Electrode means, 2,5... Excitation mechanism, 3.
6... Sample container, 11... Oxygen electrode, 12...
- Sample container, 13... Measurement solution, 14... Movable arm, 15... Fixed frame, 16... Spring, 17... Excitation coil, 18... DC power supply for bias, 19... - Excitation AC power supply, 20... Power amplifier, 21... Recording device, 31.
...Low frequency oscillator, 32...Power amplifier, 33...
DC constant voltage power supply, 34...excitation coil.

Claims (1)

[Claims] 1. A method for electrochemically analyzing a specific substrate in a solution using an electrode means, characterized by applying vibration to the solution to be measured to homogenize the solution during analysis. electrochemical analysis method. 2. A container containing a solution to be measured, an electrode means for electrochemically analyzing a specific substrate in the solution by immersing it in the solution to be measured, and applying vibration to the solution to be measured in the container. An electrochemical analysis device characterized by comprising: means.