Application of Multivariate Calibration Methods to the Simul Speetrophotometrics Determination of Zn~(2+),Cd~(2+) and Co~(2+) in Water Samples

This paper developed a simple and sensitive method,based on multivariate calibration,for the simultaneous multiwavelength spectrophotometric determination of Zn2+,Cd2+ and Co2+ in surface water samples.The method relies on the spectral differences between their complexes with 4-(2-pyridylazo)-resorcinol(PAR).The absorbance data were measured and recorded in wavelength range of 300~600 nm.It was found that both the absorbance of positive peak and negative valley are proportional to the concentration of each analyte.In addition,the results with the absorbance alterations at the two wavelengths analyzed showed that the linear ranges of each analyte at the two wavelengths were the same.Synthetic mixtures of the three metal ions were analyzed,and the data obtained with the three different wavelength ranges(i.e.,300~450 nm,450~600 nm and 300~600 nm) were processed by classical least squares(CLS),principal component regression(PCR) and partial least squares(PLS).The prediction results showed that PLS method with the spectral data in the range of 300~600 nm gives better results than the two other methods(CLS and PCR) in the the two other different wavelength ranges (450~600 nm and 300~600 nm).Following the validation of the proposed method,it was successfully applied for the determination of the three metal ions in two surface water samples.