EVALUATION OF MULTIWAVELENGTH CHROMATOGRAMS FOR THE QUANTIFICATION OFMIXTURES OF PESTICIDES BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY DIODE-ARRAY DETECTION WITH MULTIVARIATE CALIBRATION

Three multivariate calibration methods, partial least squares (PLS-1 a nd PLS-2) and principal component regression, were applied to the simu ltaneous determination of the five pesticides iprodione, procymidone, chlorothalonil, folpet and triazophos by high-performance liquid chrom atography with diode array detection. Such detection gives multiwavele ngth chromatograms from a single analysis of one sample. In this paper ,calibration models at two different wavelengths were developed to res olve mixtures of five pesticides with overlapping chromatographic peak s. The first model, carried out at 220 nm as detector compromise wavel ength, yielded satisfactory sensitivity for accurate estimation of the concentration of iprodione, procymidone, chlorothalonil acid folpet a nd the second model, at 200 nm, was used for accurate estimation of tr iazophos. Both calibration models were evaluated using the chromatogra ms and first-derivative (D-1) chromatograms by predicting the concentr ations of independent test set samples. Finally, the proposed D-1 cali bration models were successfully applied to the determination of these pesticides in groundwater and soil samples. In all cases, the PLS-1 c alibration method showed superior quantitative prediction ability than the PLS-2 or principal component regression methods. (C) 1997 Elsevie r Science B.V.