Matrix solid phase dispersion (MSPD) extraction and gas chromatographic screening of nine chlorinated pesticides in...

A multiresidue technique is presented for the extraction and quantitative gas chromatographic screening of 9 insecticides (lindane, heptachlor, aldrin, heptachlor epoxide, p,p'-DDE, dieldrin, endrin, p,p'-TDE, and p,p'-DDT) as residues in beef fat. Beef fat was fortified by adding the 9 insecticides, plus dibutyl chlorendate as internal standard, to 0.5 g portions of beef fat and blending with 2 g C18 (octadecylsilyl)-derivatized silica. The C18/fat matrix blend was fashioned into a column by adding the blend to a 10 mL syringe barrel containing 2 g activated Florisil. The insecticides were then eluted from the column with 8 mL acetonitrile, and a 2 microL portion of the acetonitrile eluate was then directly analyzed by gas chromatography with electron capture detection. Unfortified blank controls were treated similarly. The acetonitrile eluate contained all of the pesticide analytes (31.25-500 ng/g) and was free of interfering co-extractants. Correlation coefficients for the 9 extracted pesticide standard curves (linear regression analysis, n = 5) ranged from 0.9969 (+/- 0.0021) to 0.9999 (+/- 0.0001). Average relative percentage recoveries (85 +/- 3.4% to 102 +/- 5.0%, n = 25 for each insecticide), inter-assay variability (6.0 +/- 1.0% to 14.0 +/- 6.7%, n = 25 for each insecticide), and intra-assay variability (2.5-5.1% n = 5 for each insecticide) indicated that the methodology is acceptable for the extraction, determination, and screening of these residues in beef fat.