PURGE-AND-TRAP ANALYSIS OF VOLATILE HALOG ENATED ORGANIC-COMPOUNDS INFOODS USING AIR SAMPLING TUBE FOR SOLVENT DESORPTION

An analytical procedure was developed for the determination of nine vo latile halogenated organic compounds (VHCs), i e., chloroform, bromodi chloromethane, dibromochloromethane, bromoform, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene a nd tetrachloroethylene, in food samples. The method employs a purge an d trap procedure with collection on ORBO-100 (graphite carbon), common ly used for air sampling tubes for solvent desorption. Ten grams of fo od sample, 40 ml of purified water, 0.5 ml of phosphoric acid and 5 dr ops of silicone were placed in a color comparison tube (sample tube). Nitrogen as the purge gas was initiated at a flow rate of 100 ml/min f or 15 min with the sample tube held at 40-degrees-C in a water bath. T rapped VHCs were extracted from the graphite carbon absorbent with 5 m l of hexane by shaking for 20 seconds. The extract was analyzed by gas -liquid chromatography with an electron capture detector using a DB-62 4 column (0.32 min i.d. x 30 m). Quantitation limit of the nine VHCs w ere as follows: chloroform 2 ppb; bromodichloromethane 0.2 ppb; dibrom ochloromethane 0.2 ppb; bromoform 0.5 ppb; 1,1,1-trichloroethane 2 ppb ; 1,1,2-trichloroethane 3 ppb; 1,1,2,2-tetrachloroethane 0.5 ppb; tric hloroethylene 0.2 ppb; tetrachloroethylene 0.2 ppb. The recoveries of VHCs added to five kinds of food samples were 70.0-99.5%. Using the pr oposed method, 25 samples of commercial products were analyzed. Four V HCs were detected as follows: chloroform ND (below quantitation limit) approximately 45.3 ppb, bromodichloromethane ND approximately 20.3 pp b, dibromochloromethane ND approximately 3.7 ppb, 1,1,1-trichloroethan e ND approximately 2.7 ppb. Bromoform, 1,1,2-trichloroethane, 1,1,2,2- tetrachloroethane, trichloroethylene and tetrachloroethylene were not detected.