COMPUTERIZATION OF A PARC174A POLAROGRAPHIC ANALYZER

A PARC174A polarographic analyzer has been transformed into a comprehe nsive microcomputer controlled electroanalytical system by interfacing it with an IBM PC equipped with a Tecmar LabMaster data acquisition s ubsystem. Techniques implemented include square wave voltammetry, chro noamperometry, cyclic voltammetry, differential pulse, normal pulse, a nd sampled dc polarography, and stripping voltammetry which can be use d with either linear sweep, differential pulse, or square-wave techniq ues. The PARC174A functions only as a potentiostat and current to volt age converter. All the potential waveforms are generated by the D/A co nverter of the LabMaster and the current data are sampled by the A/D c onverter. The software developed should be easily adaptable to most po tentiostats with minor modification. Because no extra circuitry is des ired to complicate the system, a small-step staircase waveform is used to approximate the linear dc ramp in cyclic voltammetry, differential pulse, and sampled dc techniques. The discrepancy in results obtained using linear dc ramp and small-step staircase waveforms was carefully examined and proven to be negligible. All the techniques implemented have been shown to give theoretically predicted results. The results a re also found essentially the same as those obtained using a conventio nal PARC174A. This computer controlled system makes available the use of square wave voltammetry, which was otherwise not available on the o riginal machine. Experimental data showed that 4.76 X 10(-8) M Cd2+ co uld be quantitatively analyzed by square wave voltammetry when a dropp ing mercury electrode was used.