Solid Phase Extraction of Pesticides with Determination by Gas Chromatography

A simple, rapid, and effective method for the extraction of fifteen organochlorine and organophosphorus pesticides based on the use of solid phase Bond Elut C-18 cartridges was studied as an alternative method to those based on extraction with organic solvents. Solid phase extraction is an attractive chromatographic sample preparation technology that reduces analysis time, costs, labor, and solvent consumption relative to traditional liquid/liquid extraction methods. The sample recoveries with the use of solid phase extractions were excellent for most pesticides. Analyte concentration by a factor as great as 1000-fold was achieved readily. The adsorbed pesticides were eluted from the solid phase by an organic solvent. The influence of the elution solvent was studied. The best recoveries were obtained using methanol. The detection of the pesticides was made using OV-17 megabore capillary gas chromatography (GC) with electron capture detection. Pesticide extraction efficiencies using C- 18 cartridges ranged from 64-100%, with the exception of mirex which was 56% at 0.2 ug/L spiking levels. Recovery precision studies demonstrate that relative standard deviations range from 1 to 9%. The compounds were identified by comparing the retention time with that of a standard under the same GC conditions, and quantitation was accomplished by comparing the peak areas.