Application of solid-phase microextraction to the headspace gas chromatographic analysis of halogenated volatiles in selected foods.

Solid-phase microextraction (SPME), with the poly(dimethylsiloxane)-coated silica fiber suspended and equilibrated in the headspace, has been applied to the capillary gas chromatographic (GC) analysis of 33 halogenated volatile contaminants in model aqueous solutions and in foods. With electrolytic conductivity detection, the limits of detection in water ranged from 1.5 micrograms/kg for vinyl chloride to < or = 0.005 microgram/kg for the tri- to hexachlorobenzenes. Headspace SPME-GC shows a much greater response for the less volatile analytes than those of greater volatility, a procedure complementing headspace GC with gas sampling. In model systems or foods, increasing lipid material decreased the headspace extraction. With 50 mg of lipid, the headspace extraction decreased about 50% for analytes with LODs about 0.1 microgram/kg and by > or = 99.5% for the above chlorobenzenes. Standard addition was used to analyze a variety of beverages and dry foods and to determine the analyte partitions.