DD296360A5

DD296360A5 - ELECTROCHEMICAL DETECTOR

Info

Publication number: DD296360A5
Application number: DD34237090A
Authority: DD
Inventors: Klaus Bartels
Original assignee: Akademie Der Wissenschaften Der Ddr,De
Priority date: 1990-07-01
Filing date: 1990-07-01
Publication date: 1991-11-28

Abstract

Der elektrochemische Detektor ist fuer elektrochemische Messungen in leitelektrolytfreien Flieszsystemen der Biotechnologie, Chemie und medizinischen Mesztechnik anwendbar. Durch ein kleines Meszvolumen, leichte Austauschbarkeit der Elektroden- und Zufuehrungseinsaetze werden eine grosze Universalitaet der Meszverfahren und Elektrodenvarianten sowie ihr reproduzierbarer Austausch erreicht.{Detektoranordnung; Flieszsystem, leitelektrolytfrei; Messung; elektrochemisch; Elektroden, austauschbar; Austausch, reproduzierbar; Universalitaet}The electrochemical detector is applicable for electrochemical measurements in conductive electrolyte free flow systems of the biotechnology, chemistry and medical Mesztechnik. Through a small measuring volume, easy interchangeability of the electrode and Zufuehrungseinsaetze a great universality of Meszverfahren and electrode variants and their reproducible exchange can be achieved {detector arrangement; Flieszsystem, electrolyte-free; Measurement; electrochemically; Electrodes, exchangeable; Exchange, reproducible; Universality}

Description

Der Schnittpunkt (7) zwischen der Längsbohrung (5) und der Querbohrung (6), durch die über den Schlauch (14) die Meßlösung zuströmt, realisiert einen seitlichen Zustrom der Meßlösung auf die Arbeitselektrode (8). Überraschenderwelse geschieht hier eine gute Durchmischung mit dem Leitolektrolyten, und der erfindungsgemäße Aufbau liefert trotz voraussichtlich inhomogener Verteilung der zu bestimmenden Stoffe im Elektrodenbereich empfindliche und reproduzierbare Meßergebnisse. Es zeigt sich, daß dieser Vorteil des erfindungsgemäßen Aufbaus des Detektors beim Einsatz von Kohlenstoffasern erhalten bleibt bzw. mit den bekannten Vorteilen der Kohlenstoffaserelektroden und insbesondere der Fasern mit ausschließlich elektroaktiver Stirnfläche (steady state des Stromsignaläs, kurze Ansprechzeit) kombinier: werden kann. Durch Einbringen einer größeren Zahl von Fasern (mehrere Tausend) werden Instabilitäten im Flüssigkeitsstrom und damit auch im chromatografischen Signal weitgehend roduziert. Die Messung ist daher stabil und reproduzierbar. Erfindungswesentlich ist, daß die beiden Bohrungen etwa senkrecht zueinander stehen, wobei Abweichungen von 90° um einen Winkel von 10° keinen entscheidenden Einfluß auf die Eigenschaften des Detektors besitzen, wenn nicht nur die Stirnflächen des Elektrodenkörpers (9) zur Messung benutzt werden, muß die Stirnfläche des Elektrodenkörpers (9) über den Schnittpunkt (7) hinausragen, und es ist vorteilhafterweise keine exakte Positionierung nötig.The point of intersection (7) between the longitudinal bore (5) and the transverse bore (6) through which the measuring solution flows via the hose (14) realizes a lateral inflow of the measuring solution onto the working electrode (8). Surprising catfish happens here a good mixing with the conductive electrolyte, and the structure of the invention provides despite presumably inhomogeneous distribution of the substances to be determined in the electrode area sensitive and reproducible results. It turns out that this advantage of the inventive construction of the detector when using carbon fibers is retained or combined with the known advantages of carbon fiber electrodes and in particular the fibers with exclusively electroactive face (steady state of Stromomsäs, short response time) can be. By introducing a larger number of fibers (several thousand), instabilities in the liquid flow and thus also in the chromatographic signal are largely produced. The measurement is therefore stable and reproducible. Essential to the invention is that the two holes are approximately perpendicular to each other, with deviations of 90 ° by an angle of 10 ° have no decisive influence on the properties of the detector, if not only the faces of the electrode body (9) are used for measurement, the End face of the electrode body (9) beyond the intersection point (7) protrude, and it is advantageously no exact positioning necessary.

Ausführungsbeispielembodiment

Das Ausführungsbeispiel zeigt auf der 'Zeichnung eine Ausführungsform des erfindungsgemäßen Detektors, bestehend aus einem Einsatz 1, der alle Teile, die der Arbeitselektrode 8 und dem Schlauch 14 für die Zuführung der Meßlösung zugehörig sind, aufnimmt und einfach von der Durchflußzelle 16 mit der Leitelektrolytlösung, die die Gegenelektrode und eine durch Membran getrennte Referenzelektrode enthält, zu trennen ist und durch einen Dichtungsring 17 zur Durchflußzelle 16 luftdicht abgeschlossen wird. Die aus dem unteren Ende 15 des Schlauches 14 austretende Meßlösung strömt den Elektrodenkörper 9 direkt an, wodurch eine hohe Empfindlichkeit und eine kurze Ansprechzeit des Detektors erreicht werden. Das Volumen der Durchflußzelle 16 wurde mit ca, 7 ml so groß bemessen, daß die Verdünnung des Leitelektrolyten infolge der zuströmenden Meßlösung über die durchschnittliche Dauer eines Chromatogramms gering bleibt. Die überschüssige Lösung verläßt durch die Ausflußöffnung 18 die Zelle. Zur Messung wurde eine wäßrige leitelektrolytfreie Lösung von Hexacyanoferrationen verschiedener Konzentrationen bis 25 pg/l durch den Schlauch (14) geleitet und reproduzierbar nachgewiesen. Der Leitelektrolyt war eine 1M KCI-Lösung.The embodiment shows in the drawing an embodiment of the detector according to the invention, consisting of an insert 1, which accommodates all parts which are associated with the working electrode 8 and the tube 14 for the supply of the measuring solution, and simply from the flow cell 16 with the Leitelektrolytlösung, which contains the counter electrode and a reference electrode separated by a membrane, is to be separated and is sealed airtight by a sealing ring 17 to the flow cell 16. The measuring solution emerging from the lower end 15 of the hose 14 flows directly to the electrode body 9, whereby a high sensitivity and a short response time of the detector are achieved. The volume of the flow cell 16 was sized at about 7 ml so that the dilution of the electrolyte as a result of the inflowing solution over the average duration of a chromatogram remains low. The excess solution leaves through the discharge port 18, the cell. For measurement, an aqueous electrolyte-free solution of hexacyanoferrations of various concentrations up to 25 pg / l was passed through the tube (14) and reproducibly detected. The supporting electrolyte was a 1M KCl solution.

Claims

1. An electrochemical detector in a 3-electrode system in a flow cell with exchangeable electrolyte, counter electrode and a separated by a membrane side vessel with a reference electrode, characterized in that in an insert (1) made of an electrically insulating material, one with a Paragraph (2) provided cylindrical upper part (3) and to the shoulder (2) tapered lower part (4) has been introduced with a continuous longitudinal bore (5) and an approximately perpendicular to this transverse bore (6) which form an intersection (7) in that a working electrode (8) is inserted into the continuous longitudinal bore (5), consisting of the electrode body (9), an electrically insulating tube (10) and an electrode connection (11) with a shank (12) such that the electrode body (9 ) at the level of the intersection (7) ends and the shank (12) in the longitudinal bore (5) is fitted, that the insert (1) to the longitudinal bore (5) p extending along the second longitudinal bore (13), which ends above the lower part (4), that through the second longitudinal bore (13) an insulating tube (14) is guided with its lower end (15) and that the insulating tube (14 ) is inserted into the transverse bore (6) and the lower end (15) is in the immediate vicinity of the electrode body (9).

2. An electrochemical detector according to claim 1, characterized in that the electrode body (9) is arranged a bundle of carbon fibers.

3. An electrochemical detector according to claim 2, characterized in that the bundles of carbon fibers are electrically insulated fibers, only their end faces are electroactive.

For this 1 page drawing

Field of application of the invention

The electrochemical detector is applicable to the determination of electroactive substances in flow systems of biotechnology, chemistry and medical measuring technology.

Characteristic of the known state of the art

Electroanalytical methods of detection in high performance liquid chromatography and flow injection analysis are indispensable for a variety of determination tasks (for review see: K. Stulik, V. Pacakova, Annali di Chimica, 76 (1986) 315, TP Tougas, Int While the flow cells of commercially available detectors are generally equipped with fixedly embedded electrodes (see, for example, LKB Electrochemical Detector Model 2143 device documentation, LKB, Sweden), more recent developments are tailored to the particular application and thus exchangeable electrodes are used (see, for example, A. Rehorek, J. Mattusch, H. Ehrhardt, L. Dunsch, DD-WP 259043, November 4, 1987) While the former can be produced simply and cheaply in a restricted field of use, the production of the latter is Detectors are relatively expensive, because all interchangeable parts manufactured with the highest precision w must ground.

Object of the invention

The object of the invention is to save working time and limit the production of different arrangements by means of a variable, standardized electrochemical detector.

Explanation of the essence of the invention

The object of the invention is to propose an electrochemical detector in which the electrode bodies are exchangeable easily and reproducibly, are used in the fiber electrodes, which is suitable for the measurement in a liquid flow low conductivity and with a stable measurement with low detection limit is possible. According to the invention, the object is achieved in that the upper part (3) receives all parts that belong to the working electrode (8) and the hose (14) for the supply of the measuring solution, and simply from the flow cell (16) with the Leitelektrolytlösung, the contains the counter electrode and a reference electrode separated by membrane, is to be separated. This advantageously allows easy cleaning and reliable replacement of the supporting electrolyte. The interchangeability of the working electrode (8) and its reproducible insertion relative to the point of intersection (7) are realized by the shape of the shank (12), the electrode terminal (11) and the longitudinal bore (5).