Comparative Performance of EC Detectors

There has been much discussion as to which mode of ED, i.e. amperometric or coulometric, is best , and secondly which manufacturer s instrument, in either configuration, is best . In nearly all cases best was judged by sensitivity towards a selected analyte or group of analytes, usually catecholamines. Such comparisons can sometimes be made, for example, with UV detectors under standard test conditions. However, for EC detectors such comparisons are rather simplistic due to the chemical nature of the ED process. 

Some of the comparisons are described below, but the results must be interpreted with due caution particularly in view of continuing improvements in detector design. One report compared two coulometric detectors for catecholamine analysis and concluded that they were equivalent to current amperometric detectors. Another study compared wall-jet and thin-layer cell configurations. Other more comprehensive studies have been controversial. Forzy et al compared 11 detectors for the analysis of 5-hydroxyindoleactic acid (5-HIAA). They used the same HPLC system with each detector to determine linearity, repeatability, absolute sensitivity, limit of detection and stabilisation time. Driebergen and Benders evaluated 10 detectors with respect to their suitability for routine use in a pharmaceutical company using tetramethylbenzidine as the test compound. Both of these reports found similar relative results with respect to sensitivity and ease of use but stressed the importance of matching instrument to application. 

Detection based on electrical and electrochemical measurements in Detectors for Liquid Chromatography, E.S. Yeung (ed.), Wiley, New York, Chapter 7, 1986. 

Electrochemical techniques for detection in HPLC in Selective Sample Handling and Detection in High Performance Liquid Chromatography (J. Chromatogr. Library 39A), R.W. Frei and K. Zech (eds). Chapter 6, Amsterdam, Elsevier, 1988, 309-363. 

Hanekamp and H.J. van Nieuwkerk, Theoretical considerations on the performance of electrochemical flow-through detectors. Anal Chim. Acta, 1980, 121, 13-22. 

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