JP5360907B2 - Electrode for organic compound detection and electrochemical detection device for organic compound concentration using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic compound concentration detecting terminal and a method for electrochemically detecting the concentration of an organic compound, which can use an electrode made of conductive diamond-like carbon, without use of expensive conductive diamond, and thereby analyze the concentration of an organic compound with high sensitivity and at high speed. <P>SOLUTION: A terminal for use in detection of the concentration of an organic compound is characterized by being a conductive diamond-like carbon electrode. In an device for electrochemically detecting the concentration of an organic compound in a sample from a measured current value and an analytical curve of the organic compound concentration and the current value by disposing a working electrode and a counter electrode in a flow cell into which the sample is fed and applying a voltage to both electrodes, the working electrode 2 is a conductive diamond-like carbon electrode, and the conductive diamond-like carbon electrode has a conductivity of 0.002 Scm<SP>-1</SP>or higher. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

TECHNICAL FIELD The present invention relates to an organic compound concentration detection electrode capable of analyzing an organic compound concentration with high sensitivity and high speed, and an organic compound concentration electrochemical detection apparatus using the same.

In recent years, the concentration of various organic compounds has been measured in disease diagnosis and the like. Taking diabetes as an example, the number of diabetic patients continues to increase. Diagnosis of diabetes has been conventionally performed by measuring blood glucose level, but it requires blood collection and analysis, and is difficult to say as a simple method. Currently, the urine sugar quantification method put into practical use in the medical field uses the coloration of enzyme reagents such as glucose oxidase as a judgment. In Japan, the judgment drug manufactured by Sanwa Chemical Laboratory Co., Ltd. Almost half of the market.

In addition, as an electrochemical analysis method for measuring the amount of sugar in the body, the hydrogen peroxide produced by the reaction of glucose oxidase (glucose oxidase) to blood glucose (glucose) in the blood is electrochemically quantified, and the blood glucose level is determined. A method using a non-enzymatic direct electrolysis sensor is known in which glucose is directly oxidized on the electrode surface and the glucose concentration is calculated from the oxidation current value.

  As a glucose concentration electrochemical analysis method, Patent Document 1 is selected from the group consisting of conductive diamond and nickel, copper, gold, platinum, palladium, ruthenium, iridium, cobalt, and rhodium supported thereon. A diamond electrode and a counter electrode are prepared, the diamond electrode and the counter electrode are brought into contact with the test sample, and the diamond electrode is placed on the diamond electrode between the diamond electrode and the counter electrode. In the test sample, the voltage at which oxidation reaction occurs is measured, the current value under the voltage is measured, and the glucose concentration in the test sample is compared with the calibration curve of the glucose concentration and the current value prepared in advance. A method for calculating the concentration of is disclosed.

JP 2002-310977 A

  In the glucose sensor method, there is a possibility that a large error occurs in the glucose measurement value due to the influence of a reducing substance such as ascorbic acid coexisting in the body fluid. For this reason, simplification of the measurement method and improvement in analysis accuracy are required for diagnosis in medical institutions and application as a portable in-vivo sugar content measuring device by diabetic patients themselves. Furthermore, the sensor part used in this method is generally disposable, but from the viewpoint of application to a simple health care device, improvement of the durability of the sensor part is also required.

In the method using the non-enzymatic direct electrolysis sensor, a very large overvoltage is required for the oxidation of glucose. In a general noble metal electrode, an oxidation product is adsorbed on the electrode surface (forms a passive film), and further, There is a problem of inhibiting the oxidation and detection of glucose.

The conductive diamond described in Patent Document 1 is expensive because the substrate material that can be formed is limited to silicon or the like, and it is a long-time film formation that requires 12 hours to form a thin film that can be formed into an electrode. It has become.

Accordingly, the present invention provides an organic compound capable of analyzing the concentration of an organic compound with high sensitivity and high speed using a diamond-like carbon (DLC) electrode having conductivity without using expensive conductive diamond. An electrode for concentration detection and an organic compound concentration electrochemical detection device using the same are provided.

The invention of claim 1, to use the detection of glucose concentration electrodes are conductive 0.002Scm ^-1 or more, potential window of 2.5V or more, the peak intensity of the amperometric response of + 3% accuracy of it made of diamond-like carbon film comprising diamond-like carbon electrode, glucose concentration detection electrode which is a conductive diamond-like carbon electrodes hydroxyl radicals in the diamond-like carbon electrode surface by the high potential applied to generate There is .

According to a second aspect of the invention, is arranged the working electrode and the counter electrode in the flow cell specimen is supplied, a voltage is applied to both electrodes, the measured current value and the glucose concentration - the concentration of glucose in the sample from the calibration curve of current values in the electrochemical detection apparatus of the glucose concentration to be detected is an electrochemical detection apparatus glucose concentration, characterized in that the working electrode is a glucose concentration detection electrode according to claim 1.

  In the present invention, the DLC film can be formed on the surface of various materials such as an alumina surface in a short time of several tens of minutes and at a low cost of 1/20 of that of conductive diamond. Further, the DLC film has performance equivalent to that of conductive diamond. As a result, high sensitivity and stable measurement are possible.

According to the present invention, since the oxidation potential is very high, an organic compound that is difficult to measure a current directly derived from oxidation using a general electrode such as platinum or graphite is used as a target substance. By selecting a conductive DCL electrode as an electrode material that can oxidize an organic compound having a high oxidation potential without being hindered by the generation reaction, and that has a property that the organic compound does not adhere to the surface. Sensitivity and simple analysis are possible.

On the surface of the conductive DCL electrode of the present invention, by applying a high potential, a hydroxyl radical that is an intermediate of the oxygen generation reaction is generated. When this hydroxyl radical is applied to the oxidation of an organic compound, the current response of the oxidation product Quantitative analysis of organic compounds is possible.

According to the present invention, it has become possible to quantitatively analyze glucose by a simple method without an enzyme, which could not be quantitatively analyzed by the enzymatic method without using glucose oxidase. In addition, quantitative analysis can be performed without causing inactivation of the electrode, which is a problem in the conventional direct oxidation method.

It is a figure which shows the electrochemical sensor system incorporating the electroconductive DLC electrode of this invention. It is a figure which shows the electrode potential dependence of the response electric current with respect to 10 mM glucose. It is a figure which shows the glucose concentration dependence of a response electric current. It is a figure which shows the electric current response (applied voltage: + 3.60Vvs, Ag / AgCl) with respect to 10 mM glucose by the electroconductive DLC electrode using a flow injection. It is a figure which shows the electrode potential dependence of the response electric current with respect to 200 mM 2-propanol. It is a figure which shows 2-propanol density | concentration dependence of a response current. It is a figure which shows the electrode potential dependence of the response electric current with respect to 200 mM ethyl acetoacetate. It is a figure which shows the ethyl acetoacetate density | concentration dependence of a response current. It is a figure which shows the electrode potential dependence of the response electric current with respect to 200 mM ethyl acetate. It is a figure which shows the ethyl acetate density | concentration dependence of a response current. It is a figure which shows the electrode potential dependence of the response electric current with respect to 10 mM ascorbic acid. It is a figure which shows the ascorbic acid density | concentration dependence of a response electric current.

  Embodiments of the present invention will be described with reference to the drawings.

The conductive DLC film is a group III and group V element, preferably nitrogen, boron, more preferably nitrogen, in order to impart conductivity with plasma irradiation output on a Si substrate using a plasma CVD method. The film is formed while controlling the amount. The amount of introduction is appropriately determined within a range where conductivity can be imparted, but the film is formed so that the number of nitrogen atoms is about 8% with respect to the number of carbon atoms so that the film thickness is 1,000 nm to 2,000 nm. It is preferable to do this. Examples of the compound containing a nitrogen atom in the molecule include hydrogen cyanide (HCN), acetonitrile (CH ₃ CN), ethane cyanide (CH ₃ CH ₂ CN), propane cyanide (CH ₃ CH ₂ CH ₂ CN), formamide (HCONH) ₂ ), acetamide (CH ₃ CONH ₂ ), methylamine (CH ₃ NH ₂ ), ethylamine (CH ₃ CH ₂ NH ₂ ) and the like. Among these compounds, one kind can be used as a raw material gas.

The conductivity of the conductive DLC used for the electrode of the present invention is 0.002 Scm ⁻¹ or more, more preferably 0.01 Scm ⁻¹ or more.

  The potential window of the conductive DLC used for the electrode of the present invention is 2.5 V or more, more preferably 3.0 V or more.

Since the conductive DLC film has excellent corrosion resistance to strong acids, it has high electrochemical stability. In addition, the conductive DLC film has a larger potential window than Pt and graphite, has a slow reaction rate of O ₂ and H ₂ generation on the surface, and becomes a polarizable electrode equivalent to conductive diamond. In addition, since the conductive DLC film has good responsiveness equivalent to that of conductive diamond with respect to the oxidation reaction of organic compounds, it can be applied as a biological component detection sensor.

In the diagnosis of diabetes, generally, as a standard for diagnosing diabetes by measuring urine sugar level, if the urine sugar value is 100 to 500 mg / dL after meal, it is a glucose tolerance disorder (boundary type), and 50 mg / dL before meal. If it is more than 500 mg / dL after meal, it is set as diabetes. The glucose concentration in the blood is in the range of 3-8 mM in adults. By using a conductive DLC thin film and applying a high potential, the glucose concentration can be measured within the above concentration range, and diabetes diagnosis can be easily performed in a short time.

In the present invention, the sensing part of the electrochemical sensor type biological component analyzer using the conductive DLC electrode adopts a flow cell configuration in which the specimen is supplied in a flow state, and the measurement current value of the electrochemical sensor is calibrated. Determine the concentration by comparing to the line.

In FIG. 1, a working electrode 2, a counter electrode 3, and a reference electrode 4 are arranged in a flow cell 1 into which a specimen flows, and an ammeter 5 that measures current values of the working electrode 2, the counter electrode 3, and the reference electrode 4 is connected. . The working electrode 2 is a conductive DLC electrode. The counter electrode uses platinum, carbon, gold or the like.

A known electrode can be used as the reference electrode, and a silver-silver chloride electrode, a saturated calomel electrode, a standard hydrogen electrode, a mercury mercury chloride electrode, a hydrogen palladium electrode, and the like are preferable.

In the present invention, the voltage applied between the DLC electrode as the working electrode and the counter electrode is not particularly limited as long as an oxidation reaction or a reduction reaction of the sample to be detected occurs on the DLC electrode.

The current value measured by the ammeter 5 is input to the current value comparison / concentration calculation unit 7 having the calibration curve data 6 of the sample concentration and the current value, and the sample concentration is calculated and displayed on the indicator 8.

The detection target sample is a substance that undergoes an electrolytic reaction on the DLC. Specifically, an organic compound having a secondary hydrogen or a tertiary hydrogen bonded to carbon adjacent to a hydroxy group, an oxy group, or a carbonyl group can be given. Among these, glucose, 2-propanol, ethyl acetoacetate, ethyl acetate, and ascorbic acid can be mentioned.

The detection target sample may be blood, body fluid, or the like derived from a living body considered to contain the above compound, or food or a diluted solution or suspension of food. In the case of a detection target sample containing various components, it is desirable to supply the sample to the flow cell after passing through a separation column.

(Manufacture of conductive diamond-like carbon)
[Production and evaluation of diamond-like carbon]
As a plasma CVD apparatus, a BP-1 product manufactured by Samco Co., Ltd., having a configuration capable of supplying negative bias power to the electrode on which the substrate is placed, was used. As the source gas, acetonitrile vaporized by heating at 50 ° C. was used. Then, a diamond-like carbon film was formed on the silicon wafer placed on the electrode so as to have a thickness of 1500 nm.
The plasma output was 230 W under the conditions that the flow rate of acetonitrile was 5 sccm, the pressure in the chamber was 10 Pa, and the temperature was 280 ° C.

(Evaluation of potential window)
Using the diamond-like carbon obtained above as the working electrode, Ag / AgCl as the reference electrode, platinum as the counter electrode, and measuring the current against the potential when the potential is swept at a rate of 100 mV / s in a 0.1 M sulfuric acid aqueous solution. did. When a potential range in which the oxidation / reduction current is ² mA / cm ² or less is defined as a potential window, the potential window is 3.94V.

(Detection of glucose concentration)
FIG. 2 shows the electrode potential dependence of the current response when 20 μL of a 10 mM glucose solution was injected using a pH 1 phosphoric acid solution as the mobile phase solution. In FIG. 2, a response current derived from glucose is observed from around + 2.0V, and the response current saturates from around + 3.6V.
As shown in FIG. 3, when the electrode potential was fixed at +3.6 V, the response current showed a linear relationship with the glucose concentration in the range of 10 mM to 1 mM. The detection limit for S / N = 3 is 1.37 mM. Therefore, it is possible to quantitatively analyze the glucose concentration by this method, and glucose can sufficiently cover the adult male body concentration value of 3 to 8 mM.
In addition, measurement of a biological component of glucose requires a highly sensitive and stable measurement. As shown in FIG. 4, in the amperometric response of the conductive DLC thin film, the peak intensity showed an accuracy of + 3% or less, and high reliability was realized.

(Detection of 2-propanol concentration)
A method similar to the detection of glucose concentration was used except that a 200 mM 2-propanol solution was used. FIG. 5 shows the electrode potential dependence of the current response. In FIG. 5, a response current derived from 2-propanol is observed from around +1.6 V, and the response current is saturated from around +3 V.
As shown in FIG. 6, when the electrode potential was fixed at +3.3 V, the response current showed a linear relationship with the 2-propanol concentration in the range of 40 mM to 200 mM. The detection limit for S / N = 3 is 5.6 mM. Therefore, it is possible to quantitatively analyze the 2-propanol concentration by this method.

(Detection of ethyl acetoacetate concentration)
A method similar to the detection of glucose concentration was used except that a 200 mM ethyl acetoacetate solution was used. FIG. 5 shows the electrode potential dependence of the current response. In FIG. 5, a response current derived from ethyl acetoacetate is observed from around + 2V, and the response current saturates from around + 3.4V.
As shown in FIG. 6, when the electrode potential was fixed at +3.6 V, the response current showed a linear relationship with the ethyl acetoacetate concentration in the range of 80 mM to 200 mM. The detection limit for S / N = 3 is 11.2 mM. Therefore, it is possible to quantitatively analyze the ethyl acetoacetate concentration by this method.

(Ethyl acetate concentration detection)
A method similar to the detection of glucose concentration was used except that a 200 mM ethyl acetate solution was used. FIG. 5 shows the electrode potential dependence of the current response. In FIG. 5, a response current derived from ethyl acetate is observed from around + 2.3V, and the response current saturates from around + 3.6V.
As shown in FIG. 6, when the electrode potential was fixed at +3.6 V, the response current showed a linear relationship with the ethyl acetate concentration in the range of 140 mM to 200 mM. The detection limit for S / N = 3 is 19.6 mM. Therefore, it is possible to quantitatively analyze the ethyl acetate concentration by this method.

(Detection of ascorbic acid concentration)
A method similar to the detection of glucose concentration was used except that a 10 mM ethyl acetate solution was used. FIG. 5 shows the electrode potential dependence of the current response. In FIG. 5, a response current derived from ascorbic acid is observed from around +0.6 V, a current peak is shown around 2 V, and the response current saturates from around +3.3 V.
As shown in FIG. 6, when the electrode potential was fixed at +3.6 V, the response current showed a linear relationship with the ascorbic acid concentration in the range of 0.1 mM to 10 mM. The detection limit for S / N = 3 is 0.014 mM. Therefore, it is possible to quantitatively analyze the ascorbic acid concentration by this method.

1: Flow cell 2: Working electrode
3: Counter electrode reference electrode 4: Reference electrode 5: Ammeter 6: Calibration curve data 7: Current value comparison / concentration calculation unit 8: Indicator

Claims (2)

To use for the detection of glucose concentration electrodes are conductive 0.002Scm ^-1 or more, potential window of 2.5V or more, consisting of amperometric peak intensity of the response is + 3% accuracy of diamond-like carbon film An electrode for detecting glucose concentration, which is a diamond-like carbon electrode, which is a conductive diamond-like carbon electrode that generates hydroxyl radicals on the surface of the diamond-like carbon electrode when a high potential is applied . The working electrode and counter electrode are arranged in the flow cell to which the sample is supplied, voltage is applied to both electrodes, and the glucose concentration in the sample is detected from the measured current value and glucose concentration-current value calibration curve. An electrochemical detection apparatus for glucose concentration, wherein the working electrode is the electrode for detecting glucose concentration according to claim 1 .

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