Simultaneous determination of cobalt and nickel. Comparison of prediction ability of PCR and PLS using original, first and second derivative spectra

Abstract

Two multivariate calibration methods, partial least squares (PLS) and principal component regression (PCR), were applied to the simultaneous determination of the divalent ions of nickel and cobalt based on the formation of their complexes with 4-(2-pyridylazo) resorcinol (PAR). The original, first and second derivative absorption spectra of the binary mixtures were used to perform the optimization of the calibration matrices by the PLS and PCR methods. The results obtained by the application of the different chemometric approaches are discussed and compared. The Savitzky–Golay convolution method is used for calculating the first- and second-derivative absorption spectra of binary mixtures. Calibration matrices were 15–540 and 15–560 ng ml −1 for cobalt and nickel, respectively.