EP0417347A1
Expired / Lapsed
EP
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Electrochemical detector
Assignee: Hewlett Packard GmbH Germany
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Filing: 1989-09-15
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Granted: —
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Expires: 2009-09-15
Abstract
Abstract An electrochemical detector comprising an electrochemical cell (11), a working electrode (1), an auxiliary electrode (2), a reference electrode (3), a potentiostat (4), and a circuit (7,8) for deriving a signal indicative of the current developed at the working electrode additionally comprises means for monitoring and determining the potential of the reference electrode (3). These means comprise an electrometer circuit (9) which can be connected via a switch (S2) to the auxiliary electrode (2) to measure the potential of the reference electrode. During the measurement, the working electrode (1) is disconnected from the circuit (7,8) which is at the same time connected to the electrometer circuit (9) via switch (S1). The invention permits to recognize measuring errors associated with instabilities in the reference electrode potential.
Inventors
- 👤 Thomas Dörr
- 👤 Clemens Linowski
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 17:30
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/26; G01N27/416; G01N27/49; G01N27/4163
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
232 words
An electrochemical detector for detecting electroactive substances, comprising: - an electrochemical cell (11) for receiving liquid including the substances to be detected, - a working electrode (1), an auxiliary electrode (2), a reference electrode (3), said three electrodes (1,2,3) being in conductive connection with the liquid in the electrochemical cell (11), - a potentiostat (4) for maintaining during electrochemical detection a constant potential difference between the liquid in the electrochemical cell (11) and the working electrode (1), with the potentiostat being coupled during electrochemical detection to the reference electrode (3) and to the auxiliary electrode (2), - signal processing circuitry (7,8) for deriving an electric signal (U out ) indicative of the current created at the working electrode (1) by electroactive substances, characterized by monitoring means for determining and monitoring the potential of the reference electrode (3) , said monitoring means comprising: - disconnecting means (S1) for disconnecting the working electrode (1) from the signal processing circuitry (7,8), - grounding means (S3) for applying a predetermined potential to the end of the reference electrode (3) opposite to the end in contact with the electrochemical cell (11), and - switching means (S2) for disconnecting the auxiliary electrode (2) from the potentiostat (4) and for connecting the auxiliary electrode (2) to an electrometer circuit (9), said electrometer circuit being operative to perform a substantially currentless measurement of the potential of the reference electrode (3).
Claim 2
Dependent Claim
232 words
An electrochemical detector for detecting electroactive substances, comprising: - an electrochemical cell (11) for receiving liquid including the substances to be detected, - a working electrode (1), an auxiliary electrode (2), a reference electrode (3), said three electrodes (1,2,3) being in conductive connection with the liquid in the electrochemical cell (11), - a potentiostat (4) for maintaining during electrochemical detection a constant potential difference between the liquid in the electrochemical cell (11) and the working electrode (1), with the potentiostat being coupled during electrochemical detection to the reference electrode (3) and to the auxiliary electrode (2), - signal processing circuitry (7,8) for deriving an electric signal (U out ) indicative of the current created at the working electrode (1) by electroactive substances, characterized by monitoring means for determining and monitoring the potential of the reference electrode (3) , said monitoring means comprising: - disconnecting means (S1) for disconnecting the working electrode (1) from the signal processing circuitry (7,8), - grounding means (S3) for applying a predetermined potential to the end of the reference electrode (3) opposite to the end in contact with the electrochemical cell (11), and - switching means (S2) for disconnecting the auxiliary electrode (2) from the potentiostat (4) and for connecting the auxiliary electrode (2) to an electrometer circuit (9), said electrometer circuit being operative to perform a substantially currentless measurement of the potential of the reference electrode (3).
Claim 3
Dependent Claim
44 words
An electrochemical detector as in claim 1, wherein the disconnecting means (S1) are also operative to connect the signal processing circuitry (7,8) to an output of the electrometer circuit (9) when the working electrode (1) is disconnected from the signal processing circuitry (7,8) .
Claim 4
Dependent Claim
24 words
An electrochemical detector as in claim 1 or 2 , wherein the measured potential of the reference electrode (3) is displayed to a user.
Claim 5
Dependent Claim
52 words
An electrochemical detector as in any of the preceding claims, wherein the potential of the reference electrode (3) is measured several times over a period of time such as to detect any drift of this potential, and wherein electrochemical detection is only enabled if the detected drift is below a predetermined value.
Claim 6
Dependent Claim
108 words
An electrochemical detector as in any of the preceding claims, wherein: - the potentiostat comprises an operational amplifier (4) having a non-inverting input connected to a source for providing an adjustable input voltage U in , and an inverting input connected to the reference electrode (3), - the grounding means comprise a switch (S3) arranged between the output of the operational amplifier (4) and the reference electrode (3), said switch (S3) being opened during electrochemical detection, and - the switch (S3) of the grounding means is opened and the input voltage U in is set to 0 volt during measurement of the potential of the reference electrode (3).
Claim 7
Dependent Claim
44 words
An electrochemical detector as in any of the claims 1 to 4, wherein during measurement of the potential of the reference electrode (3), the reference electrode (3) is disconnected from the potentiostat (4) and directly connected to a fixed potential, for example ground potential.
Claim 8
Dependent Claim
26 words
An electrochemical detector as in any of the preceding claims, wherein the disconnecting means (S1), the switching means (S2) and the switch (S3) comprise reed relays.
Claim 9
Dependent Claim
24 words
Use of an electrochemical detector as in any of the preceding claims for detecting the effluent of the separation column of a liquid chromatograph.
Claim 10
Dependent Claim
40 words
Use of an electrochemical detector as in claim 8, wherein the reference electrode (3) is a redox couple (for example: Ag/Ag⁺ Cl⁻) and wherein the anions of the redox couple (for example: Cl⁻ ) are provided by the mobile phase.
References Cited (Backward Citations)
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