Determination of small amounts of analytes in the presence of a large excess of one analyte from multi-analyte global signals of differential-pulse voltammetry and related techniques with the signal ratio resolution method

Abstract

The signal ratio resolution method was applied to the determination by differential-pulse voltammetry and related techniques of two analytes in presence of a large excess of a third analyte in ternary mixtures of known qualitative composition. Using the signal ratio resolution method, a global signal is divided by the individual signal of the major component, multiplied by a factor, in order to obtain a height as close as possible to the estimated contribution of the major component to the global signal. To establish possible influence of resolving the signal on the quantification, simulated differential-pulse polarograms (DPPs) were divided by the individual major component DPP having a different peak current height and different current translation values. Using theoretically simulated DPPs, it was found that two minor components can be determined with a relative error <1% for different resolving parameters (peak current height of resolving functions, current translation values and peak separations). The method was then verified on a system containing Cd at 0.3, Tl at 200 and Pb at 0.5 µmol l^–1 using differential-pulse anodic stripping voltammograms. It was shown that using this method and a system with favourable reversibility and amalgam formation, cadmium can be determined in a 200-fold and lead in a 120-fold excess of thallium, with a relative error of <10%. The main advantage of the method over other deconvolution methods is the removal of the contribution of one component from the global signal, revealing the contributions of the other components in a peak-shaped form that is linearly proportional to the analyte concentrations.