JPS5834355A - Twin electrode type voltammetry detection system - Google Patents

Abstract

PURPOSE:To eliminate an electrolytic current by disturbing substance, by applying different electric potential to a working electrode provided in a flow cell and subtracting or adding the electrolytic current obtained from each electrode. CONSTITUTION:A flow cell 1 is provided a counter electrode 10, a reference electrode 11 and working electrodes 13, 14. A constant electric potential generator 2 is connected with the electrodes 11, 10 and also, three poles type potentiostat circuit is constituted between working electrode potential terminals 20, 21. The terminals 20, 21 are connected with each electrode 13, 14 through an inner circuit corresponding to an I-V converter 3 and mutually independent potential is applied. An output from each inner circuit is subtracted or added by an operational and electric power amplifier 4 and an electrolytic current component of disturbing substance other than measuring object substance is eliminated and computed output is recorded on a recorder 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel measurement system and measurement method using a twin-electrode portammetry detector.

Portammetry detectors with a 70-cell structure, which are used as detectors in liquid chromatographs, microliquid chromatographs, flow injection analyzers, and other chemical separation and analysis devices, generally have one working electrode and a In an electrode configuration consisting of a counter electrode and a reference electrode, a desired voltage between one working electrode and another electrode is applied by a three-electrode potentiometer circuit, and the sample in the 70-cell is electrochemically detected.

In such a detector, the separated components to be detected,
Relationship with other substances may cause measurement instability or inaccuracy. In other words, if you want to detect only oxidizing or reducing substances at a specific potential, if you use the three-electrode DC voltage method, if there is a substance that reacts at a lower potential than the substance to be detected, it will be detected as a pre-discharge substance. As a result, a current superimposed on the electrolytic current of the target substance is generated. Therefore, this pre-discharge substance becomes an interfering substance.

In such cases, an AC polarograph, di 7 allencial pulse polarograph (D, P.

P, ) etc. are said to be useful, but their influence cannot be ignored.

In order to solve the problems in the flow cell type portammetry detector as described above, the present invention forms two working electrodes (twin electrodes) in the flow cell and applies different potentials to these electrodes. In addition, these separately drawn electrolytic currents are subtracted or added. In this case, the electrical N-paths for separately drawing electrolytic current from the two working electrodes are calibrated to produce the same output signal when the same potential is applied to those electrodes and the same sample is analyzed. Ru.

As a result, by applying the potential of the target substance reservoir to one working electrode and a lower potential to the other working electrode, the electrolytic current of the latter is subtracted from the electrolytic current of the former electrode. The electrolytic current component of the reacting substance (interfering substance) is substantially removed.

In this case, since the potential of each working electrode is constant, the influence of the stored electric current can of course be ignored.

Similar benefits are obtained in schemes where the oxidation potential for a particular reversible oxidation-reduction substance is applied to one working electrode and the reduction potential to the other working electrode. In other words, the difference in electrolytic current between the electrodes for both cases is the difference between the positive current (oxidation current) and the fI current (reduction current due to reversible reduction of the oxidized component) for the specific component (reversible reactant). , the result is the sum of their absolute values, which is theoretically the same form as amplification. For example, if there is an irreversible oxidation component, it will not produce a reduction current, and therefore will not be amplified by the subtraction of the electrolytic current.

In addition, in the above voltage application method, when two electrolytic currents are added, the irreversible component is only the electrolytic current on the side where the reaction occurred, so this value is maintained, and the reversible reaction component is the positive current and negative current. Theoretically, it is reduced by the sum of the currents, making it possible to effectively detect irreversible components.

As described above, the present invention provides a technique for analyzing specific components with high sensitivity and good reproducibility. especially,
According to the present invention, it is clear that even if interfering components that cannot be separated by chromatography are mixed with or in close proximity to the target component, the target component can be effectively measured if there is a difference in oxidation or reduction potential.

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

In FIG. 1, (1) is a micro flow cell, (21
is a constant potential generator, (3) is a D-V converter, (4) is an operational amplifier and power amplifier for subtraction or addition, (5) is an attenuator, (6) is a recorder, and (7) is a medium heat treatment equipment.

The micro flow cell (1) has a liquid inlet (9) in the upper block (8), a liquid outlet and counter electrode (101, and the old reference electrode).
The lower block 121 has first and second working electrodes (I3) and 141. Between the upper block [81 and the lower block (121), there is a narrow flow channel (15) communicating with the liquid inlet +91 and the liquid outlet f1.01.
is formed, and has an electrode surface that contacts the sample variety flowing in each army W flol, 1llll131 and h (15).

The constant potential generator +2+ is connected to the reference electrode 1ll by the line (I6) and the reference terminal circle is connected to the reference electrode 0011C by the line (181!+9).
and working electrode potential terminals (20) and (21).
) between the three-electrode potentiostat l[
- constitutes. The working electrode potential terminals 1201 and +211 are connected to the working electrodes (131 and 1), respectively, through corresponding internal circuits of the IV converter (3).Therefore, the IV converter (3) is connected to the working electrode It includes mutually independent internal circuits for independently applying a potential to (13 and
If the same potential is applied to 14 and the same sample is measured, the gain can be adjusted so that the two outputs have the same value. Operational amplifier and power amplifier (4)
The two outputs of the I-V converter (3) are subtracted or added to appropriately amplify the power, and the calculated and amplified output is sent to the attenuator (5).
After being appropriately attenuated, the signal is recorded on a recorder (61).

The selection of subtraction and addition by the arithmetic operation and power amplifier (4), the attenuation rate of the attenuator (5), etc. can be commanded by the central processing unit (7).

Next, an example of a portammel-IJ-detection method using the above configuration will be described.

Figure 2 shows various components in a biological sample containing catecholamines plus an internal standard sample, using a multi-electrode in which the applied voltage of one working electrode is sequentially changed or several working electrodes are specially formed. This is a voltamodalum obtained by simultaneously applying mutually different potentials to the plurality of working electrodes of a type flow cell. The components represented by each curve are
NE (norepinerelin) in catecholamines, E (
epinephrine), DA (dopamine), and metabolites NM (normetanephrine) and VM that are mixed in biological samples.
A (paneer mandelic acid), T in amino acids
yr (tyrosine) and DHBA as an internal standard sample
(3,4-dihydroxybenzylamine). Note that the working electrode is platinum, and the counter electrode is silver/silver chloride.

Therefore, first, let's look at 1 in Figure 2. Focusing on the gradient of each component between OV and 0.8V, the current change is most remarkable between those voltages, followed by MA4'$, and the stability rates of catecholamines and 5-part standard samples are extremely small. I understand that. FIG. 3 shows the working electrode W1α3 in the twin-electrode portammetry detector of the present invention.
) to 1ooomV4, working electrode W2O41 to BoomV
This graph shows the difference in electrolytic current obtained by applying various components separated by chromatography to the detector flow channel. It is a graph showing the difference between That is, W, −W2
The graph shows that a specific component (in this case,
Tyr and VMA) can be clearly detected.

Figure 4 shows the difference in BoomV and Wl for similar samples.
This is a graph when 600 mV is applied to . In this case, the most obvious T at 1000m100O'Om■
Since yr does not react below 700 mV, W, (B
There is only a small peak at 0mV), and the change in current for NM, which is a substitute substance, is the largest (VMA follows), and the others are also small.

Next, Figure 5 shows the case where BoomV is applied to Wl and 300 mV is applied to Wl. In this case, the Wl-Wl graph shows that catecholamines NB, E, and DA can be clearly detected along with the internal standard sample DHBA. ing.

While Figures 3 to 5 above relate to the analysis of differential specific components, the graph in Figure 6 shows an effective method for detecting reversible reaction components (catecholamines and internal standard samples). As is clear from Figure 2, the oxidation initiation potential of these components is slightly lower than 0°4V, and Wl is 40V.
If 0 mV and 20 omV are respectively applied, W
These oxidation currents flow through l, and these reduction currents flow through Wl. The directions of these currents are opposite, and as a result, the 'w, -'w2 graph represents the sum of the absolute values of both flows, and each peak of the Wl graph (and W2 graph, not shown) is amplified. It is shaped like this. Therefore, it is clear that even if an irreversible component is detected at either electrode, this component will not appear in an amplified form in the W-W2 graph.

Conversely, to draw the w, -1-w2 graph, Wl
By adding the electrolytic currents of and Wl, reversible components such as catecholamines and internal standard samples are canceled out, and irreversible components that can be detected by either electrode remain unchanged in size.
It will appear in the l + W2 graph.

As described above, the present invention applies different potentials to two working electrodes and calculates the difference or sum of electrolytic currents flowing through these electrodes, thereby reducing components other than the target components accurately and with high sensitivity. This makes it possible to obtain portammetry.

Note that when adding both electrolytic currents, if the potentials of the corresponding two working electrodes are made the same, it is theoretically possible to obtain a component peak that is amplified twice.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the system of the present invention, Figure 2 is a portamograph of a biological sample containing catecholamines and an internal standard sample, Figures 3 to 6 are chromatograms expressed by the electrolytic current of one of the two working electrodes, and This is a comparison of graphs showing the difference between the chromatograms of both electrodes. 11------Twin electrode type holtammetry detector f9+----One liquid inlet (IQ+---One liquid outlet and counter electrode 11.11---One reference electrode 0.31---- -1 First working electrode a41---Second working electrode---1-Flow channel Patent applicant Yanagimoto Seisakusho Co., Ltd. Agent Kenbu Shinten (1 other person) () Rent
Mae ≧ Sen -Origai 282- Figure 5 ■ [ 6 - La Gambling Proceedings Amendment Commissioner of the Patent Office Mr. ■ Display of the case Patent Application No. 134574 of 1982 3
Relationship with the case of the person making the amendment Name of patent applicant Yanagimoto Seisakusho Co., Ltd. 4, Agent
604 6. Number of inventions increased by amendment 7. Subject of amendment Full text of specification 8. Contents of amendment (1) Engraving of specification (no change in content) 9 List of attached documents

Claims (7)

[Claims] (1) A flow cell type portammetry detector including at least two working electrodes and one counter electrode, and constant potential generation for applying different potentials to the two working electrodes with respect to the counter electrode. and a constant potential applied @1 line formed between the constant potential generator and the two working electrodes to separately detect electrolytic currents flowing to the corresponding working electrodes. two IV converters; and a difference output device for each output signal of the two IV converters. (2) the two I-V converters include gain control circuits calibrated so that they produce the same output signal when applying the same potential to each corresponding working electrode and analyzing the same sample; Detector according to claim 11, characterized in that: (3) The flow cell type portammetry detector has a reference electrode in addition to the working electrode and the counter electrode, and the constant potential generator has a potential of two points between each working electrode and the working electrode and the counter electrode based on the potential of the reference electrode. The detector according to claim 1 or claim 2, wherein the detector is configured as a polar potentiostat circuit. (4) In a flow cell type portammetry detector having two working electrodes, a potential for detecting a target component is applied to the first working electrode, and the first working electrode is applied to the second working electrode. Applying a potential lower than the electrode potential,
By detecting the electrolytic currents flowing through each of the first, second, and second working electrodes and determining the difference between signals corresponding to the detected electrolytic currents, electrolysis is performed by the potential applied to the second working electrode. A twin-electrode portammetry detection method characterized by substantially eliminating the influence of interfering components and quantifying target components. (5) In the detection of each electrolytic current by the two working electrodes, each detection gain generates the same output signal when applying the same potential to the corresponding working electrode and analyzing the same sample. 4. The method according to claim 4, wherein the method is calibrated as follows. (6) Applying an oxidation potential for a reversible oxidation-reduction component to the first working electrode in a flow cell type portammetry detector having two working electrodes, and applying a reduction potential to the second working electrode. Then, the electrolytic current flowing through each of the two working electrodes is detected separately, and the electrolytic current corresponding to the electrolytic current is 6.
A twin-electrode polcunmetry detection method characterized by reducing interference caused by reducing components and detecting the reversible acid (e-reducing component) in an amplified manner. (7) In a flow cell type portammetry detector having two working electrodes, an oxidation or reduction potential of an irreversible oxidation or reduction component is applied to the first working IK electrode, and the second working electrode applying a reversible reaction potential for a reversible oxidation-reduction component to be oxidized or reduced by the potential of the first working electrode, detecting the electrolytic current flowing through each of the two working electrodes separately; Twin-electrode portammetry detection characterized in that by determining the sum of each electrolytic current, the interference of the reversible acid-reducing component is inherently removed and irreversible oxidation or reduction components are quantified. Method.