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Evaluation of Dispersive & Cartridge Solid Phase Extraction (SPE) Cleanups

for Multiresidue Pesticides in QuEChERS Extracts of Finighsed Tobacco Using GCxGC-TOFMS

Tobacco is a high-value production crop for the United States and ranks 6th in the amount of pesticides applied per acre in American agriculture. Even after the processing of tobacco, some pesticide residues remain on the final product. We used the quick-easy-cheap-effective-rugged-safe (QuEChERS) sample preparation approach to isolate residues prior to anlyzing pesticides in tobacco. We evaluated the cleanup efficacy and pesticide recoveries for different formulations of QuEChERS dispersive solid phase extraction (dSPE) cleanup and the more traditional cartridge solid phase extraction (cSPE) cleanup. Comprehensive two-dimentional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS) was used to determine pesticide residues in the resulting extracts. The results of the cleanup evaluation indicated that the dSPE cleanup formulation with 7.5mg of carbon (versus 50 mg) provided the best recovery of targeted pesticides. The average recoveries for the 500 ppb spike level and 50 ppb spike level were 92% (13% RSD) and 91% (22% RSD) respectively.

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