Multivariate optimization of the voltammetric determination of Cd, Cu, Pb and Zn at bismuth film. Application to analysis of biodiesel

In the present work, the simultaneous optimization of multiple responses was applied to the optimization of the simultaneous determination of trace levels of Cd(II), Cu(II), Pb(II) and Zn(II) via anodic stripping voltammetry (ASV) at a bismuth film electrode. Two different approaches were evaluated: i) use of individual responses such as peak current and its coefficient of variation; and ii) use of the full-voltammogram by means of a recent chemometrics method named analysis of variance-principal component analysis (ANOVA-PCA). Deposition time and voltage step were the most important factors identified with both optimization procedures. The optimized method was applied to the determination of trace levels of Cd(II), Cu(II), Pb(II) and Zn(II) in biodiesel samples after microwave digestion with diluted acid, presenting satisfactory values for accuracy and precision. For 0.1 g of digested biodiesel sample, the values found for the limits of quantification were 0.23 μg g− 1 for Cd, 0.09 μg g− 1 for Cu, 0.39 μg g− 1 for Pb, and 3.5 μg g− 1 for Zn.