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

A 4-channel computer controlled potentiostat has been designed (expand able to 16 channels) for use with an amperometric array for analysis i n flowing streams. The instrumentation developed to date has been used with both linear and radial flow cell configurations. Analogue and di gital circuits for the independent control of 4 working electrodes hav e been fabricated, tested and integrated successfully to give an amper ometric array. The design is based on the utilisation of common refere nce and counter electrodes to reduce the complexity of the electrode a rrangement. Control of the purpose built instrumentation is effected w ith a 486-33 MHz personal computer and Analog Devices RTI815 and RTI81 7 data acquisition/control cards which are responsible for hardware co ntrol functions and data acquisition via digital and analogue control lines. Software for instrumentation control, data display (2- or 3-dim ensional formats), on-line and post-run data processing and storage ha s been developed using the QuickBASIC software environment. The user i nterface utilises a Windows style display to achieve user friendliness with an on-line help facility. Data is stored in a spreadsheet compat ible format (ASCII with '','' column delimiter) to facilitate post-run processing with standard applications packages such as Microsoft EXCE L. The system has been applied to the determination of well characteri sed electroactive compounds using now-injection analysis. Linearity ov er 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 s imultaneous measurement of both oxidation and reduction now injection currents of hexacyanoferrate(III) and hydroquinone is demonstrated.