| Abstract: | Beef and pork fat, corn, peanut, rapeseed and paraffin oils, as well as vegetable shortening were used to investigate their suitability as fortification media for environmental chemicals in the evaluation of the sweep co-distillation technique. The animal fats produced considerable gas chromatographic background interference, while the oils were partly carried over during the sweep co-distillation process, except for rapeseed and peanut oil. Residue free rapeseed oil was fortified with 26 environmental chemicals in several groups at 20 and 200 ng/g of oil. Recoveries for most compounds were greater than 80% with a coefficient of variation of less than or equal to 10. At the 20 ppb fortification level, recoveries for Aroclor 1260, Mirex and pentachlorobenzene were only 70-80%. A similar low recovery was observed for p,p'-DDT, Mirex, hexachloro-1,3-butadiene, while at the 200 ppb level, 1,2,4-trichlorobenzene was only 33% recovered. The sweep co-distillation technique was further evaluated by using rendered human fat and the same fat diluted with residue free peanut oil. Residue levels in diluted and non-diluted fat were in good agreement, except for hexachlorobenzene. These residue levels were further compared with those obtained by two other cleanup procedures: Florisil-silicic acid column chromatography and low temperature precipitation. In general the sweep co-distillation technique compared favourably with these other cleanup procedures. There was evidence, however, that p,p'-DDT broke down into p,p'-TDE and varying operating procedures did not completely remedy this situation. |
