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For the risk assessment of human exposure to volatile halogenated hydrocarbons, a dynamic purge trap/on-column cryofocusing method using capillary gas chromatograph-63Ni electron capture detector and thermal desorption unit was applied to analyze the free forms, metabolites of 1,1,2-trichloroethylene and 1,1,2,2-tetrachloroethylene. The urine sample was diluted with distilled water, hydrolyzed and sealed. Then the inert gas was infused to purge out free 1,1,2-trichloroethylene, free 1,1,2,2-tetrachloroethylene and trichloroethanol. These compounds were trapped to TenaxR GC-gas trap device throughout clean up tube. Being undetectable to gas chromatograph directly, trichloroacetic acid was methyl esterificated and trapped in the manner above mentioned. The optimal incubation time to get best recovery of methyl ester was 4 hours at 60oC. The concentrations of free volatile halogenated hydrocarbons and their metabolites in urine were obtained from 5 healthy volunteers. This analytical method is expected to make the biological monitoring, more precise and convenient.
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