The simplified amperometric detection scheme demonstrated is based on the amperometric working and electrophoretic ground electrodes only. The latter serves as counter and pseudo-reference as well. It is shown via the successful determination of neurotransmitters, ascorbic acid and phenols on gold or platinum working electrodes that this approach is feasible for detection on a channel based electrophoretic separation device. Also presented is the detection of carbohydrates and amino acids with copper electrodes. The results were found to be similar to those obtained with conventional capillary systems with amperometric detection, albeit at much reduced analysis times.

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Singly charged amines and sulfonic acids as cationic and anionic aliphatic model substances, respectively, were detected in capillary electrophoresis with all-solid-state ion-selective electrodes. The sensitivity for these compounds is a function of their lipophilicity. The signal detected is generally greater for molecules with a larger organic part. The utility of the method is further demonstrated by the detection of a group of aromatic compounds in the form of the anionic analgesics (S)-(+)-2-(4-isobutylphenyl)propionic acid, 2-[(2,6-dichlorophenyl)amino]benzeneacetic acid, and o-acetylsalicylic acid. Further determined were the artificial sweeteners cyclamate, acesulfame-K, and saccharin. Detection limits for the different substances were between 2.5 × 10(-)(6) and 1 × 10(-)(5) M.

The design of a new amperometric detector for capillary electrophoresis is described. By employing the electrophoretic counter electrode as a polarized pseudo-reference electrode with an appropriate electronic circuitry it was possible to carry out the detection with a single electrode, the working electrode which is mounted in the wall jet arrangement. It is demonstrated that this approach delivers reliable results which are comparable to those obtained with conventional three-electrode potentiostat arrangements. Detection of catecholamines, ascorbic acid, carbohydrates, and heavy metals using different working electrodes is demonstrated, these being examples of possible applications. The simplicity and robustness of the detector cell make it well suited for its use in a field-portable instrument.

Portable instrumentation has become of increasing interest in analytical chemistry, because on-site analysis has various advantages. In this report we describe the construction of a field-portable capillary electrophoresis instrument with potentiometric detection. The apparatus is contained in a PVC case of 340 3 175 3 175 mm size and a total weight of 7.5 kg and can therefore be carried easily by one person. Two lead-acid batteries provide the power for a high voltage module capable of supplying up to 30 kV, and for the detection amplifier electronics. As detectors, miniature coated-wire ion-selective electrodes are used and a precise electrode alignment is achieved by a simple electrode holder cell without the need for a microscope. Data acquisition is carried out by a small analog-to-digital converter board, which is integrated into the unit, and a palmtop personal computer. The instrument was tested on the banks of the river Rhine. As examples, alkali and alkaline earth metal cations and inorganic monovalent anions were analysed in the river water.

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