Economic method for analysis of fluid milk for organochlorine residues at the 10 ppb level

A procedure is described to isolate and clean up organochlorines in fluid milk for gas chromatographic (GC-ECD) analysis. Extraction and cleanup are performed in the same glassware, an ordinary separatory funnel. The only chemicals needed are H2SO4 and petroleum ether. Size of milk samples is versatile provided proportions of the chemicals are adjusted accordingly. Recoveries greater than 80% are obtained for 18 common organochlorines added to the milk which correspond well with recoveries with official methods for determining incurred residues. The proposed procedure shows a low lipid carryover (about 1%), and extraneous interferences are minimal. Its inherent simplicity makes the method suitable for standardization, and the small number of operations permit semi- or full automation.