Rapid Screening Method for DDT in Milk with Gas Chromatography

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Abstract
A method is presented for assay of DDT and DDE. Milk is hydrolyzed with alcoholic KOH and extracted once with hexane. A 50-[mu]1 portion of extract, equivalent to 50 mg milk is injected into a chromatograph having an electron affinity detector. The column consists of two aluminum segments, a 6-in and a 6-ft length, 1/4 in O.D., packed with CaC2 (20/30 mesh) and Fluoropak 80 coated with Silicon Dow 11 and Epon Resin 1001. For our work temperature of oven housing column and detector was 200[degree]C and flow rate of carrier gas, nitrogen, was 210 ml/min. Calibration curves were prepared by plotting peak heights against known concentrations of DDE and used for computing unknown concentrations in milk. An average recovery of 95 [plus or minus] 7.7% was obtained when either p,p[image]-DDT or DDE was added to milk at 0.04 to 0.12 ppm. The standard deviations in all recovery studies were homogeneous with a value of [plus or minus] 0.107 cm peak height or [plus or minus] 0.003 ppm DDE. Comparison of results obtained on split milk samples by this technique and by paper chromatography showed no significant differences. The method is simple and accurate. In 1 workday 20-25 samples can be analyzed by one technician with one instrument.