A FLEXIBLE INSTRUMENT FOR VOLTAMMETRY, AMPEROMETRY AND STRIPPING POTENTIOMETRY

A computerized system capable of performing the techniques most commonly encountered in electroanalysis is described. The system consists of a personal computer with peripherals which controls several units, both commercially available and purpose-built, for data acquisition and experimental control. In addition, several optional devices such as pumps, valves, and a sample carousel may be controlled for automation of the analytical procedures. A main feature of the software is that it permits complex experiments and advanced data processing to be defined as a sequence of much simpler commands. Several of these may be gathered in a command macro which then is available as a single command. The data acquisition used for stripping potentiometry has been improved and now utilizes an A/D converter of the track and follow type, specially adapted for the purpose. The result is evident in terms of smoother stripping signals with high resolution on the potential axis, and the high sampling rate of maximum 800 kHz permits signals from analytes at the low mu g/l level to be well-resolved even with moderate pre-electrolysis times. Precise timing of the pulsed amperometric and voltammetric techniques, independent of the execution speed of the program, is achieved by means of three counters in cascade counting clock pulses. The A/D converter is paced by one of those while another one times various delay periods. This facilitates high sampling rates to be combined with real-time display of the data. Three applications demonstrating the merits of the system are included. One of these compares the signal quality obtained with the improved data acquisition with that of an older apparatus for stripping potentiometry. Next the utility of comparing several sampling techniques when optimizing an analytical procedure is demonstrated for the determination of Pb in samples with very high salt content. Finally, the possibility of building highly automated analytical procedures by means of the command macros is shown for the amperometric detection of carbohydrates at a Cu electrode in a flow-injection set up.