Extraction Procedure. Fillion, et al., used an acetonitrile extraction with a first cleanup with a C18 cartridge followed by an additional cleanup with carbon SPE cartridge coupled to an aminopropyl cartridge cleanup to remove co-extractives. Determination of pesticides was by GC with mass-selective detection in the selected-ion monitoring mode and liquid chromatography with post-column reaction and fluorescence detection for N- methyl carbamates (Fillion, et al. 2000). We used a 1 g sample versus the 50 g sample used by Fillion and co-workers, thus our method required less solvent (30 mL vs. 105 mL) and a smaller sample size. We modified the QuEChERS and Fillion methods (22,
Extraction Procedure. Extraction was performed with the liquid-liquid extraction methodology and 100mL of the sample was measured with a graduated cylinder and extracted with 20mL of dichloromethane (DCM) in a separatory funnel. The mixture was shaken for 2 minutes and allowed to separate for 5 minutes. The bottom layer was decanted into a pre-cleaned and labeled flask and wrapped in foil. This step was repeated twice per sample (60 mL DCM total) and all samples were stored in the refrigerator until GC-FID analysis. The separatory funnels were cleaned between sample extractions with a detergent and tap water rinse followed by deionized water rinse. The funnel was then rinsed with acetone and again with dichloromethane. A clean-up step was deemed unnecessary since the samples were well and borehole water that were not notably contaminated with other particulate matter.
