JPH0629873B2 - Enzyme functional electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an enzyme functional electrode, that is, a substance that can be a substrate for an oxidase enzyme such as glucose or galactose present in an electrolyte, lactic acid, alkose, glycerol, or the like. The present invention relates to an electrode for amperonatrically measuring the concentration of a substance that can be a substrate for the dehydrogenase enzyme of the above.

(B) Prior art The applicant of the present invention has proposed that an electron carrier is used as an electrode for measuring the concentration of a substance that can be a substrate of an oxidase enzyme such as glucose or galactose present in an electrolyte or a substance that can be a substrate of a dehydrogenase enzyme such as lactic acid or alcohol. We have applied for an enzyme functional electrode in which an enzyme is immobilized on a paste-like electrode containing a body.

(C) Problems to be Solved by the Invention The above-mentioned enzyme functional electrode has a drawback that it is easily affected by an oxidizable substance present in a sample, such as ascorbic acid or uric acid.

(D) Means for solving the problem The present invention has been made in view of the above, and a paste electrode containing an electron carrier in the paste, and an enzyme immobilized on the surface of the paste electrode. And a substrate-sensing portion composed of a permeable thin film of an immobilized enzyme substrate covering the outer surface of the enzyme-functional electrode, wherein a grid electrode is provided on the surface of the substrate-sensing portion. And

The grid electrode is synonymous with a porous electrode.

(E) Action The present invention oxidizes the oxidizable substance existing in the sample in advance by the grid electrode arranged on the surface of the substrate sensitive part, and prevents the generation of current by the oxidizable substance at the measurement potential. .

(F) Examples Examples of the present invention will be described below.

(A) Preparation of Electrode First, 100 mg of graphite powder, 60 μ of liquid paraffin and 48 mg of benzoquinone were mixed well, filled in a glass tube and compressed, and one end was flattened to prepare a quinone-carbon paste electrode.

Next, glucose oxidase solution (30 μg
／ 30μ), evaporate the water, and the diameter is 4.8m.
Permeable thin film (dialysis membrane, thickness 20μ
m), a gold mini-grid electrode (500 μi manufactured by Interconic, grid width 14 μm, hole width 37 μm, thickness 3.3 μm) is further placed thereon, and a glass tube and a quick-drying epoxy resin are used for attachment. A lead wire is attached to one end of the gold mini-grid electrode using a conductive adhesive. When the gold mini grid electrode is glued to the glass tube, the dialysis membrane is also fixed.

Furthermore, the gold mini-grid electrode and its lead wire are insulated and fixed using a quick-drying epoxy resin. The lead from the carbon paste electrode can be obtained by directly attaching a platinum wire into the paste electrode.

The electrode (W) produced by the above method is shown in FIG.

In the figure, 1 is a quinone carbon paste electrode, 2 is a glucose oxidase immobilization layer, 3 is a dialysis membrane, 4 is a gold mini grid electrode, 5 is a quick-drying epoxy resin, 6 is a lead wire, and 7 is a glass tube. 8 is a conductive adhesive.

(B) Measuring device The measurement was carried out by a three-electrode system using an H-shaped cell as shown in FIG. In FIG. 2, W is an electrode 8 in FIG. 1 which is a glass H-shaped cell,
9 is a Teflon (registered trademark) tube for nitrogen ventilation, 10 is a silicon stopper for fixing an electrode, 11 is a stirrer, 12 is KCl
Saturated agar, 13 is a platinum counter electrode, 14 is a saturated calomel electrode, 1
5 is a saturated KCl solution, a is a terminal for a carbon paste electrode,
b is a terminal for a gold mini grid electrode, c is a counter electrode terminal for a carbon paste electrode, d is a counter electrode terminal for a gold mini grid electrode,
e is a reference electrode terminal.

The connection between these terminals and the potentiostat is shown in FIG. WE, CE, RE are working electrodes (carbon paste electrode,
Gold mini grid electrode), counter electrode, reference electrode. I
Is a paste electrode system potentiostat, II is a grid electrode system potentiostat, and III is a recorder.

(C) Measurement The effect of ascorbic acid on the glucose concentration measurement was measured.

The measurement was carried out by first putting a base solution (0.1 M, PH7.0 phosphate buffer solution) into the H-type cell 8 and removing oxygen with nitrogen gas.

The potential of the carbon paste electrode was +0.5 V (VSSCE), and a steady current dependent on the glucose concentration was shown when no potential was applied to the grid electrode (circuit off). This current value was also almost the same as that without the mini grid electrode. Furthermore, even if a potential of 0.5 V (VSSCE) was applied to the grid electrode 6, there was no change in the glucose response.

When the grid electrode 6 is turned off, a current response of about 0.85 μA for 2 mM glucose is observed. When ascorbic acid is added to this, an increase in the steady-state current value according to the ascorbic acid concentration is recognized as shown by the straight line A in FIG. Next, when a potential of 0.5 V (VSSCE) was applied to the grid electrode, the response to glucose did not change, and the current value did not change depending on the ascorbic acid concentration (Fig. 3, line B).

This means that by applying the same potential as that of the enzyme functional electrode for glucose measurement to the grid electrode 6, most of the oxidizable interfering substances that affect glucose measurement at that potential are removed by the grid electrode and do not interfere with glucose measurement. Is shown.

Further, it is possible to quantify the concentration of ascorbic acid from the difference in the current value flowing through the carbon paste electrode 1 when the grid electrode 6 is turned on and off. Note that the amount of ascorbic acid can be similarly determined by the value of the current flowing through the grid electrode 6.

(G) Effect According to the present invention, there is an effect that the concentration of the target substance can be measured without being interfered with by the oxidizable substance present in the sample.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrode according to the present invention, FIG. 2 is a schematic diagram of a measuring cell, FIG. 3 is a connection diagram of a cell and a potentiostat, and FIG. 4 is an influence of ascorbic acid on glucose concentration measurement. FIG. 1 ... Quinone carbon paste electrode 2 ... Glucose oxidase immobilization layer 3 ... Dialysis membrane, 4 ... Gold mini grid electrode 5 ... Epoxy resin, 6 ... Lead wire 7 ... Glass tube, 8 ... Conduction Adhesive

Claims (1)

[Claims] 1. A paste-like electrode in which an electron carrier is contained in a paste, an enzyme immobilized on the surface of the paste-like electrode and a permeable thin film of a substrate of the immobilized enzyme covering the outer surface thereof. An enzyme functional electrode comprising a substrate-sensitive portion composed of: wherein a grid electrode is provided on the surface of the substrate-sensitive portion.