Rapid Screening Method for DDT in Milk with Gas Chromatography

• Published in: Journal of dairy science 1963-10, Vol.46 (10), p.1025-1032
• Main Authors: Schafer, M.L., Busch, K.A., Campbell, J.E.
• Format: Article
• Language: English
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(63)89202-4

A method is presented for the assay of DDT and DDE. Milk is hydrolyzed with alcoholic KOH and extracted once with hexane. A 50-µl portion of extract, equivalent to 50mg milk, is injected into a chromatograph having an electron affinity detector (tritium). The column consists of two aluminum segments, a 6-in. and a 6-ft length, ¼ in. od, packed with CaC2 (20/30 mesh) and Fluoropak 80 coated with Silicon Dow 11 and Epon Resin 1001. For our work, the temperature of oven housing column and detector was 200C and the 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±7.7% was obtained when either p,p′-DDT or DDE was added to milk at 0.04 to 0.12ppm. The standard deviations in all recovery studies were homogeneous, with a value of±0.107cm peak height or±0.003ppm DDE. Comparison of the results obtained on split milk samples by this technique and by paper chromatography showed no significant differences. The method is simple and accurate. In one workday 20 to 25 samples can be analyzed by one technician with one instrument.