Spectrophotometric simultaneous determination of nickel, cobalt and copper by orthogonal signal correction- partial least squares

A method for the simultaneous spectrophotometric determination of nickel, cobalt and copper based on the formation of their complexes with 2-(2-Thiazolylazo)-p-Cresol (TAC) in micellar media of Triton X-100 is proposed. The absorbance spectra were recorded in the range of 500 to 800 nm. The linear concentration range for nickel, cobalt and copper in solution calibration sets were 0.05–1.80, 0.10–6.41 and 0.10–6.54 μg/ml, respectively. The effects of experimental parameters such as pH, time, concentration of ligand and surfactant on the sensitivity of method were investigated. The data obtained from the experiments were processed by the partial least squares (PLS), orthogonal signal correction-partial least squares (OSC-PLS) and principle component-back propagation artificial neural network (PC-BPANN). A set of synthetic mixtures of nickel, cobalt and copper was evaluated and the results obtained by each chemometric approaches were compared with different testing methods. The OSC-PLS method was selected because afforded better results than the others. The method was satisfactorily applied for determination of nickel, cobalt and copper in alloy samples. The accuracy was determined using comparing the results to the reference values and also independent analysis by flame atomic absorption spectrometry.