Genetic algorithm applied to selection of wavelength in partial least squares for simultaneous spectrophotometric determination of nitrophenol isomers

Ternary mixtures of nitrophenol isomers have been simultaneously determined in synthetic and real matrix by application of genetic algorithm and partial least squares model. All factors affecting the sensitivity were optimized and the linear dynamic range for determination of nitrophenol isomers found. The simultaneous determination of nitrophenol mixtures by using spectrophotometric methods is a difficult problem, due to spectral interferences. The partial least squares modeling was used for the multivariate calibration of the spectrophotometric data. A genetic algorithm is a suitable method for selecting wavelength for PLS calibration of mixtures with almost identical spectra without loss prediction capacity. The experimental calibration matrix was designed by measuring the absorbance over the range 300 - 520 nm for 21 samples of 1 - 20 mu g mL(-1), 1 - 20 mu gmL(-1), and 1 - 10 mu gmL(-1) of m-nitrophenol, o-nitrophenol, and p-nitrophenol, respectively. The root mean square error of prediction for m-nitrophenol, o-nitrophenol, and p-nitrophenol with genetic algorithms and without genetic algorithms were 0.3732, 0.5997, 0.3181 and 0.7309, 0.9961, 1.0055, respectively. The proposed method was successfully applied for the determination of m-nitrophenol, o-nitrophenol, and p-nitrophenol in synthetic and water samples.