DEVELOPMENT OF A COMPUTER-CONTROLLED MULTICHANNEL POTENTIOSTAT FOR APPLICATIONS WITH FLOWING SOLUTION ANALYSIS

A 4-channel computer controlled potentiostat has been designed (expandable to 16 channels) for use with an amperometric array for analysis in flowing streams. The instrumentation developed to date has been used with both linear and radial flow cell configurations. Analogue and digital circuits for the independent control of 4 working electrodes have been fabricated, tested and integrated successfully to give an amperometric array. The design is based on the utilisation of common reference and counter electrodes to reduce the complexity of the electrode arrangement. Control of the purpose built instrumentation is effected with a 486-33 MHz personal computer and Analog Devices RTI815 and RTI817 data acquisition/control cards which are responsible for hardware control functions and data acquisition via digital and analogue control lines. Software for instrumentation control, data display (2- or 3-dimensional formats), on-line and post-run data processing and storage has been developed using the QuickBASIC software environment. The user interface utilises a Windows style display to achieve user friendliness with an on-line help facility. Data is stored in a spreadsheet compatible format (ASCII with '','' column delimiter) to facilitate post-run processing with standard applications packages such as Microsoft EXCEL. The system has been applied to the determination of well characterised electroactive compounds using now-injection analysis. Linearity over the range 10(-2)-10(-7) M has been obtained with a detection limit of 2 x 10(-7) M (S/N = 3.0) for potassium hexacyanoferrate(III). The simultaneous measurement of both oxidation and reduction now injection currents of hexacyanoferrate(III) and hydroquinone is demonstrated.