Determination of Organochlorine Insecticides in Waters by Quantitative TLC and C-18 Solid Phase Extraction

Abstract

Organochlorine insecticides were extracted from water using a C-18 solid phase extraction cartridge. The concentrated pesticide residues were spotted directly for silica gel TLC separation, followed by detection with ammoniacal AgNO₃ solution and quantification by densitometric scanning. When removal of interfering constituents was required, the extract was chromatographed on a water-deactivated silica gel column. Recoveries of methoxychlor and p, p′-DDT were greater than 90% at fortification concentrations of 2.5 and 0.25 ppb for waters not requiring silica gel cleanup and greater than 85% when this step was included.