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 permeat ion chromatography (GPC), and Florisil column adsorption chromatograph y were compared as cleanup techniques for the determination of organoc hlorine pesticide residues in animal fats by Megabore capillary gas ch romatography 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 t o 0.4 mg/kg and cleaned up by each of the 3 techniques. Recoveries obt ained for all 3 methods were in the range 73-113%, with coefficients o f variation between 1.1 and 11.2%. Equivalence of method performance w as further demonstrated by performing replicate analyses of beef and s heep fat containing naturally incurred residues of heptachlor epoxide, dieldrin, p,p'-DDE, p,p'-DDD and p,p'-DDT. All 3 methods offer effect ive cleanup and acceptable recovery of organochlorine pesticides in an imal fat. The sweep codistillation method has the advantages of low so lvent and reagent use, simultaneous cleanup of 10 samples, and rapid t urnaround, although thermal degradation of p,p'-DDT requires monitorin g and control. GPC offers a high degree of automation but is a relativ ely slow sequential sample cleanup with high solvent use. Florisil col umn adsorption chromatography is a simple, proven technique but requir es considerable solvent and reagent and has a low potential for automa tion.