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A multiresidue isolation technique known as matrix solid-phase dispersion (MSPD) is presented for the extraction and subsequent gas chromatographic/electron capture detection (GC/ECD) determination of 14 chlorinated pesticides (α-BHC, (β-BHC, lindane, heptachlor, aldrin, heptachlor epoxide, p,p’-DDE, dieldrin, endrin, 4,4’-DDD, endrin aldehyde, p,p’-DDT, endosulfan sulfate, and methoxychlor) from oysters (Crassostrea virginica). Pureed whole oysters (0.5 g aliquots) are fortified with the 14 pesticides and δ-BHC, as an internal standard, and blended with 2 g C18 (octadecylsilyl)-derivatized silica. Pesticides are eluted from an extraction column composed of C18/oyster matrix blend and 2 g activated Florisil by addition of 8 mL acetonitrile-methanol (90 + 10). Then, 2 μL of the eluate is analyzed by GC/ECD. Unfortified blank controls are treated similarly. The eluate contained all the pesticide analytes and was free of interfering coextractants. Correlation coefficients for the standard curves of the 14 extracted pesticides (linear regression analysis) ranged from 0.9849 to 0.9980. Average relative percent recoveries over the range of concentrations examined (66 ± 12.7% to 84 ± 25.3%, n = 25 for each pesticide), interassay variability (13.6 ± 8.8% to 30.2 ± 9.1 %, n = 25 for each pesticide), and intra-assay variability (5.8-11.8%, n = 5 for each pesticide) indicated that the MSPD methodology successfully extracted and determined the 14 chlorinated pesticides in oyster at levels of 31.3-500 ng/g.

A multiresidue isolation technique using matrix solid-phase dispersion (MSPD) and gas chromatography/ electron capture detection is applied to crayfish (Procambarus clarkii) hepatopancreas for the extraction and determination of 14 chlorinated pesticides (α-BHC, β-BHC, lindane, heptachlor, aldrin, heptachlorepoxide, p,p'-DDE, dieldrin, endrin, 4,4'- DDD, endrin aldehyde, p,p'-DDT, endosulfan sulfate, and methoxychlor). Pureed crayfish hepatopancreata (0.5 g aliquot) are fortified with the 14 pesticides and with δ-BHC as an internal standard before blending with 2 g C18 (octadecylsilyl)- derivatized silica. The C18-hepatopancreas matrix blend and 2 g activated Florisil comprise an extraction column from which the pesticides are eluted by adding 8 mL acetonitrile. Two microliters of the eluate is directly analyzed by gas chromatography with electron capture detection. Unfortified blank controls are treated similarly. The eluate contained all the pesticide analytes and was free of interfering coextractants at most fortification levels. Correlation coefficients for the 14 extracted pesticide standard curves (linear regression analysis) ranged from 0.9685 to 0.9985. Average relative percent recoveries (recoveries for all pesticides ranged from 55 ± 10.4% to 118 ± 45.2%, n = 15 for each pesticide) over the range of concentrations examined, interassay variability (7.1 ± 5.7% to 16.0 ± 5.6%, n = 15 for each pesticide), and intra-assay variability (0.0-26.2%, n = 5 for each pesticide) indicated that the MSPD methodology allowed for the successful extraction and determination of the 14 chlorinated pesticides at 125-2000 ng/g levels in crayfish hepatopancreas.

A new multiresidue extraction technique was used to determine incurred chlorinated hydrocarbon pesticide residues in various fish species sampled at 2 locations along the Tensas River in Louisiana. Residue levels of total DDT (combined DDT, DDE, and DDD levels) in fish muscle fillets from paired samples ranged from 0.2 to 3.9 ppm on a wet weight basis. These findings were compared to those of another laboratory that used a different protocol to isolate the residues from the fish muscle fillets. This latter protocol typifies the more complicated, time-consuming protocols used by governmental agencies for screening purposes. Results demonstrated that the new extraction technique reduced analysis time, solvent waste, and cost per sample without affecting the quality of residue detection and measurement.