JPH044216Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to an electrolytic reactor for voltammetry, which has a cell structure suitable for measuring specific reversible reactants or removing impurities.

Examples of conventional configurations and their problems Electrochemical detectors are increasingly being used as flow-based detectors for liquid chromatography and flow-injection analysis, and their field of application is expanding due to their selectivity, high sensitivity, and ease of operation. It's coming. In order to increase the usefulness of such an electrochemical detector, the present inventor previously invented a structure in which a pair of working electrodes are provided, that is, a twin-electrode voltammetric detector, and for example, the first working electrode is We developed a measurement method in which a predetermined component in a sample is subjected to an electrolytic reaction, and the electrolyzed product is reversibly captured at a second working electrode. This is because when measuring a substance that exhibits a reversible electrode reaction, for example, a reducing electrode reactant such as vitamin K, the drawback that dissolved oxygen is reduced and the baseline becomes unstable can be avoided at the second working electrode. This can be resolved by reoxidation measurement. That is, although reversibly reoxidized vitamin K is captured at the second working electrode, the reduction of dissolved oxygen by the first working electrode, which is an electrolytic reactor, has no effect. In addition, as has been confirmed mainly in biological excretion samples such as catecholamines, in oxidation or reduction measurements that do not involve reversible reactions, the upstream working electrode is used to remove the effects of contaminants that are sensitive to lower potentials. Highly accurate measurements are possible.

However, in the twin electrode type flow cell as described above, since a pair of working electrodes are arranged in one channel, there is a drawback that the efficiency of the upstream working electrode as an electrolytic reactor is low.

Purpose of the invention This invention seeks to provide a column-type cell structure with improved electrolysis efficiency as an electrolytic reactor connected to the sample flow system of a voltammetric detector.

Structure of the Invention In order to achieve the above object, the electrolytic reactor of the present invention is connected to an elution channel of a liquid chromatograph, an inlet channel connected to another liquid sample flow system, and a cell inlet of a voltammetry detector. a column chamber filled with glassy carbon particles as a working electrode is formed between the inlet channel and the outlet channel; a counter electrode is provided exposed in the outlet channel; This method is characterized in that a reaction potential difference for a predetermined sample component or impurities is applied between the electrodes.

In the above electrolytic reactor, preferably a rod (1 to 3 mmφ) made of glassy carbon of the same quality as the working electrode is used as the working electrode terminal. In this way, the working electrode is made of glassy carbon particles,
The column electrode type flow-through cell structure in which the electrode terminals are made of homogeneous glassy carbon rods is a structure unique to the present invention, and has a low pore density, such as carbon fiber or glass reticulated carbon electrodes, which have been commonly used in the past. It eliminates non-uniformity and provides uniform and dense porosity. This ensures a stable electrode reaction, and the homogeneity of the electrode and electrode terminal (conventional electrode terminals used materials such as platinum that are different from the electrode) prevents the formation of an oxide film on the surface of the electrode terminal. This provides a stable electrode structure that eliminates factors that degrade electrode characteristics, such as hydrogen overvoltage.

DESCRIPTION OF EMBODIMENTS FIG. 1 is a diagram showing the flow path connections of the reactor of the present invention, in which 1 is a fluid sample supply source such as a liquid chromatograph, 2 is a column-type electrolytic reactor of the present invention, and 3 is a voltammetric reactor. Detector 4 is a recorder. The electric circuit 5 applies an appropriate electrode potential to the column-type electrolytic reactor 2 and the voltammetry detector 3, and also drives the recorder 4. With the configuration shown in FIG. 1, the column-type electrolytic reactor 2 of the present invention electrolytically reacts the reverse reaction component eluted from the chromatograph 1, and the electrolyzed product is returned to its original state in the voltammetry detector 3. The amount of re-reaction will be recorded in the recorder 4.

FIG. 2 shows an example of a specific configuration of the column-type electrolytic reactor 2 shown in FIG. In FIG. 2, 2a is a main body block made of electrically insulating material and has a cylindrical column chamber 6 extending therethrough, and 7 and 8 are an inlet block and an outlet block, respectively. It has an inlet flow path 7a and an outlet flow path 8a that communicate with each other. The inlet block 7 and the outlet block 8 are fixedly fitted into recesses formed at both ends of the main body block, and support a membrane 9 at each end. These membranes 9 allow the liquid sample to pass through without any hindrance, but block the glass particles filled in the column chamber 6 from the inlet and outlet channels 7a, 8a. The piping of the inlet channel 7a and outlet channel 8a is held within the inlet block 7 and outlet block 8 by piping blocks 10 and 11 screwed into these blocks, respectively. An electrode terminal 12 made of a glassy carbon rod that contacts the glassy carbon grains in the column chamber 6 is inserted in the lower part of the main body block 2a, and an auxiliary hole 13 communicating with the column chamber 6 is provided in the upper part of the main body block 2a. In this embodiment, this auxiliary hole 13 is always closed by a screw plug 14.

The electrode reactor of the present invention has the basic structure as described above, and in this case, the piping of the outlet channel 8a is formed of an electrode material made of a moldable anti-conductive material so as to serve as a counter electrode to the working electrode.

The example shown in FIG. 3 has essentially the same structure as that shown in FIG. 2, but a reference electrode 16 is inserted into the auxiliary hole 13 of the main body block 2a via a through screw 15. As a result, the working electrode terminal 12
The electrode potential applied between the electrode and the outlet channel 8a, which also serves as a counter electrode, can be precisely controlled by a three-electrode potentiostat circuit in which a reference electrode 16 is also interposed.

Figure 4 shows the chromatographic elution flow of catecholamine, which is a biological sample, being oxidized at a working electrode potential of 1000 mV using the electrolytic reactor according to the present invention (in this case, Figure 3) in front of a voltammetric detector. The components noradrenaline NE (#1) and dopamine DA (#1) are measured at the working electrode potential +
This is a graph measured after reduction at 200 mV.
In this graph, it can be seen that NE (#1) was measured clearly and with high sensitivity as a peak current of about 7.5 nA, and DA (#1) was measured as a peak current of about 5.5 nA. In contrast, in a conventional twin-electrode voltammetry detector, the values of the reversible reduction current measured by the second working electrode under almost the same conditions are the points NE (#2) and DA (#2) in the same graph. However, the low peak current coupled with the large base fluctuations and noise components (not shown) was achieved by using the electrolytic reactor of the present invention, which achieved extremely high sensitivity and stability. It can be seen that the measurement was possible.

Effects of the invention As explained above, it is clear that by using the electrolytic reactor of the invention, selectivity is superior and highly sensitive and stable sample measurement becomes possible. In addition, this electrolytic reactor cell can be used as a guard cell to adsorb components that may degrade the electrode surface of an electrochemical detector, such as lipids in a sample, such as when measuring biological components. .

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the flow path connection of the electrolytic reactor of the present invention, Fig. 2 is a cross-sectional view showing the structure of an embodiment of the electrolytic reactor of the present invention, and Fig. 3 is a cross-sectional view showing a modification thereof. , FIG. 4 is a graph showing the test results of the electrolytic reactor of the present invention in comparison with the conventional method. 1...Liquid chromatograph, 2...Column type electrolytic reactor, 3...Voltammetry detector, 4...
...Recorder, 5...Electric circuit, 2a...Main block, 6...Column chamber, 7, 8...Inlet and outlet block, 7a...Inlet channel, 8a...Outlet channel and counter electrode, 10, 11... Piping block, 12... Electrode terminal, 13... Auxiliary hole, 14... Screw plug, 15
...Through screw, 16...Reference electrode.

Claims (1)

[Claims for Utility Model Registration] (1) Having an elution channel of a liquid chromatograph, an inlet channel connected to another liquid sample flow system, and an outlet channel connected to a cell inlet of a voltammetry detector. A column chamber filled with glassy carbon particles as a working electrode is formed between the inlet channel and the outlet channel, a counter electrode is provided exposed in the outlet channel, and a predetermined sample component is placed between these electrodes. Or an electrolytic reactor for voltammetry, characterized in that a reaction potential difference for impurities is applied. (2) The electrolytic reactor according to claim 1, wherein the working electrode terminal that contacts the glassy carbon grains in the column chamber is made of a glassy carbon material.