Comparison of gel permeation chromatography, sweep codistillation, and Florisil column adsorption chromatography as sample cleanup techniques for the determination of organochlorine pesticide residues in animal fats.

Methods using a commercial sweep codistillation apparatus, gel permeation chromatography (GPC), and Florisil column adsorption chromatography were compared as cleanup techniques for the determination of organochlorine pesticide residues in animal fats by Megabore capillary gas chromatography with electron capture detection. Animal fat that had been previously found to contain no detectable organochlorine residues was spiked with 17 organochlorine pesticides at levels ranging from 0.1 to 0.4 mg/kg and cleaned up by each of the 3 techniques. Recoveries obtained for all 3 methods were in the range 73-113%, with coefficients of variation between 1.1 and 11.2%. Equivalence of method performance was further demonstrated by performing replicate analyses of beef and sheep fat containing naturally incurred residues of heptachlor epoxide, dieldrin, p,p'-DDE, p,p'-DDD and p,p'-DDT. All 3 methods offer effective cleanup and acceptable recovery of organochlorine pesticides in animal fat. The sweep codistillation method has the advantages of low solvent and reagent use, simultaneous cleanup of 10 samples, and rapid turnaround, although thermal degradation of p,p'-DDT requires monitoring and control. GPC offers a high degree of automation but is a relatively slow sequential sample cleanup with high solvent use. Florisil column adsorption chromatography is a simple, proven technique but requires considerable solvent and reagent and has a low potential for automation.