USE OF PRINCIPAL COMPONENT ANALYSIS FOR STUDYING THE SEPARATION OF PESTICIDES ON POLYETHYLENE-COATED SILICA COLUMNS

The retention time of 27 pesticides was determined on an polyethylene- coated silica high-performance liquid chromatography column (PEEsil) u sing water-methanol mixtures as eluents. Linear correlations were calc ulated between the logarithm of the capacity factor and the methanol c oncentration in the eluent (C) and the relationship between the slope and intercept values of the above correlation, the hydrophobicity, spe cific hydrophobic surface area of the pesticides and their retention p arameters on porous graphitized carbon column was elucidated by using principal component analysis followed by two-dimensional nonlinear map ping. The most polar pesticides showed irregular retention behaviour o f the PEEsil column, their retention decreased with increasing concent ration of methanol in the eluent. This irregular retention was tentati vely explained by the silanophile effect: at higher methanol concentra tions the polar substructures of pesticides have a higher probability of binding to the polar adsorption centers on the silica surface not c overed by the hydrophobic ligand increasing in this manner the retenti on capacity of the support Principal component analysis showed that PE Esil support has retention characteristics different from those of tra ditional reversed-phase supports. (C) 1998 Elsevier Science B.V.