RETENTION BEHAVIOR OF SOME COMMERCIAL PESTICIDES ON A POROUS GRAPHITIZED CARBON COLUMN

The retention of 30 commercial pesticides was determined on a porous graphitized carbon column (PGC) using dioxane and water mixtures as eluents. Linear correlations were calculated between the log k' values and the dioxane concentration (c) in the eluent, the intercept (log k'(0)) and slope (b) values were regarded as the best estimations of the retention capacity and the contact surface area of the pesticides with the stationary phase. Both the slope and intercept values showed high variations suggesting that PGC can be successfully used for the separation and quantitative determination of pesticides. The retention capacity of pesticides significantly depended both on their Lipophilicity (R(MO)) and specific hydrophobic surface area (HSA) determined by reversed-phase thin-layer chromatography, indicating that the lipophilicity parameters of solutes have a significant impact on their retention capacity on a PGC. The relatively low ratio of variance suggested that factors other than hydrophobicity parameters may have a considerable influence on the retention. Principal component analysis followed by cluster analysis revealed that the hydrophilicity parameters of the pesticides also influence their retention behaviour on a PGC.