Analytical control of organic additives in electrolytic baths by UV spectroscopy in combination with multivariate analysis

A method for the simultaneous determination of organic additives in Zn(II) and Ni(II) electrolytic baths is proposed. Absorbance and first-derivative spectra were subjected to direct and, inverse multiple linear regression (CLS and ILS, respectively) in order to choose the optimum alternative. The use of a factor design to prepare the samples enables the identification of interactions between analytes and their correction by ILS. The results provided by first-derivative spectra were slightly better than those obtained with absorbance spectra (prediction errors were always less than 2% with the former). The ILS procedure was applied to three industrial baths used to a different extent, with highly satisfactory results.