1Department of Chemistry, Faculty of Sciences, K. N. Toosi University of Technology, Tehran, I. R. IRAN
2Department of Chemistry, Faculty of Sciences, Razi University, Kermanshah, I. R. IRAN
3Researches and Petroleum Engineering Center of Kermanshah, Kermanshah, I. R. IRAN
Direct orthogonal signal correction(DOSC) and Savitzky-Golay filters (SGF) were applied as preprocessing methods on the original and first derivative absorbance data. Principle component regression (PCR), partial least squares (PLS) and iterative target transformation factor analysis (ITTFA), were used in spectrophotometric simultaneous determination of heavy divalent metal ions, lead, zinc,mercury and cadmium,using 4-(2-pyridylazo) resorcinol (PAR) as metallochromic indicator. The optimum values of the parameters for DOSC and SGF were obtained according to REP, R2 and RMSEP functions for calibration and prediction sets. The concentration for Hg2+, Pb2+, Zn2+ and Cd2+ ions in calibration set were varied between 0 - 12.24, 0 - 9.81, 0 - 0.87 and 0 - 3.96 ppm, respectively. The experimental calibration set was composed of 35 sample solutions and the 7 solutions as prediction set using a simple lattice (4,4) mixture design. The absorption spectra were recorded from 450 to 600 nm and absorbance data were autoscaled. The effect of pH on the sensitivity and selectivity was studied in the range of 1.00 - 11.00 and pH=7.50 was chosen according to net analyte signal (NAS) as a function of pH.
 Andersson, C. A., Chemom. Intell. Lab. Sys., 47, 51 (1999).
 Savitzky, A., Golay, M. J. E., Anal. Chem., 36, 1927 (1964).
 Press, W. H., Teukolsky, S. A., Wetterling W.T., Flanerry B. P., “Numerical Recipes In C: The Art of Scientific Computing”, Cambridge University Press., Chap. 14, Statistical Description of Data (1992).
 Gorry P. A., Anal. Chem., 62, 570 (1990). and Signal Processing Toolbox: sgolayfilt command.