COMPARATIVE QUANTITATIVE-ANALYSIS OF OVERLAPPING VOLTAMMETRIC SIGNALS

Catalytic hydrogen evolution according to the Brdicka reaction was applied for the rapid detection and determination of metallothionein isolated from rabbit liver. The heights of two catalytic hydrogen waves, of different widths, Cat1 (overlapped with the reduction wave of Co2+) and Cat2 (overlapped with Cat1) were evaluated as non-resolved peaks by polarography or by manual tangent fitting and after signal deconvolution applying windowing or straight-line subtraction, as the difference between the current at the peak potential and the baseline at the same potential. Calibration straight lines were statistically verified and compared. Additive interference of the overlapping peaks is the cause of the systematic error of the calibration straight lines. After deconvolution the interference was diminished but not completely eliminated. A significant improvement was achieved for the Cat1 signal, applying deconvolution with straight-line subtraction. In this manner concentrations of metallothionein as low as 19 mug l-1 could be determined. The sensitivity of the calibration straight line of the Cat1 peak is nine times higher than that of the Cat2 peak. The error of the calibration straight line intercept for the Cat2 peak is similar irrespective of whether it is evaluated as the unprocessed signal by manual tangent fitting or after deconvolution with straight-line subtraction.