Correction for Background Current in Differential Pulse, Alternating Current, Related Polarographic Techniques in the Determination of Low Concentrations with Computerized Instrumentation

Modern electroanalytical techniques, such as differential pulse and alternating current polarography, can be used to accurately determine concentrations of electroactive species at 10-7 M concentration levels, or below, provided the background current can be corrected for. Using computerized instrumentation, a quadratic least squares fit of data removed from the faradaic peak current of interest is shown to provide a general method of predicting the base line over all of the required potential range. Since no theoretical assumptions are involved in the calculation, contributions from residual oxygen levels or other trace impurities are included in the background prediction and correction procedure, the method is applicable to a wide range of techniques and conditions. Results are presented for the determination of cadmium in the 10-6 to 10-8 M concentration range in 1 M NaCI, data at these very low concentration levels are generally found to be superior to those obtained by storing a polarogram f the blank in memory and subsequently subtracting the result from test solutions.