SEPARATION OF PESTICIDES ON AN OCTADECYL-COATED ALUMINA COLUMN

The retention times of 33 commercial pesticides were determined on an octadecyl alumina HPLC column using water-methanol mixtures. The reten tion of the pesticides decreased with an increasing concentration of m ethanol in the eluent proving the regular retention behaviour of the s olutes. The retention characteristics of pesticides did not correlate to their hydrophobicity parameters indicating that the absorption cent ers of alumina not covered by the hydrophobic octadecyl ligand conside rably influence the retention. The opposite linear correlation between the retention of pesticides on alumina and octadecyl alumina supports proves that octadecyl alumina supports behave as real reversed-phase supports, however, their retention characteristics differ considerably from those of traditional octadecylsilica supports.