Determination of organochlorine pesticides in sediment using graphitized carbon black solid-phase extraction and gas chromatography/mass spectrometry

An analytical method for the determination of organochlorine pesticides (OCPs) in sediment samples involves ultrasonic extraction, solid-phase extraction (SPE), gas-chromatography (GC)/electron-capture detection (ECD), and GC/mass spectrometry (MS). OCPs were extracted from sediment samples by ultrasonication in mixtures of n-hexane and acetone. Several SPE sorbents [Florisil, silica gel, C18, Oasis HLB, and graphitized carbon black (GCB)] were evaluated as means of preliminary purification. GCB SPE cartridges successfully removed major contaminants such as non-polar hydrocarbons when eluted with an acetone-acetonitrile mixture. After purification, the extract was preferentially screened using GC/ECD and confirmed and quantified using GC/MS. The percentage recovery of samples spiked with 10 or 100ng/g OCP ranged from 73.9% to 106.0% with a relative standard deviation of 0.4-5.7%. Detection limits ranged from 0.002 to 0.005ng/g for GC/ECD and from 0.03 to 0.50ng/g for GC/MS detection. The linear dynamic range extended from 0.2 to 20ng/g, with a correlation coefficient (R(2)) greater than 0.995. The method was validated using a standard reference material (SRM 1941b) and spiked sediment samples. Real sediment samples collected from a river near a Korean industrial area exhibited low levels of several OCPs when analyzed using this method.