Simplex design method in simultaneous spectrophotometric determination of silicate and phosphate in boiler water of power plant and sewage sample by partial least squares

Partial least squares modeling as a powerful multivariate statistical tool was applied to the simultaneous spectrophotometric determination of silicate and phosphate in aqueous solutions. The concentration range for silicate and phosphate were 0.02-0.6 and 0.4-3 μg ml-1, respectively. The experimental calibration set was composed with 30 sample solutions using a mixture design for two component mixtures. The absorption spectra were recorded from 500 to 900 nm. The optimum conditions were obtained by simplex optimization method. The values of root mean square error of prediction (RMSEP) for silicate and phosphate using partial least squares (PLS) were 0.0017 and 0.02 μg ml-1, respectively. The effects of various cations and anions on detection of silicate and phosphate were investigated. The method was successfully used for determination of silicate and phosphate in boiler water at power plant, well water and sewage samples.