An analytical procedure was developed for the determination of nine volatile halogenated organic compounds (VHCs), i. e., chloroform, bromodichloromethane, dibromochloromethane, bromoform, 1, 1, 1-trichloroethane, 1, 1, 2-trichloroethane, 1, 1, 2, 2-tetrachloroethane, trichloroethylene and tetrachloroethylene, in food samples. The method employs a purge and trap procedure with collection on ORBO-100 (graphite carbon), commonly used for air sampling tubes for solvent desorption. Ten grams of food sample, 40ml of purified water, 0.5ml of phosphoric acid and 5 drops of silicone were placed in a color comparison tube (sample tube). Nitrogen as the purge gas was initiated at a flow rate of 100ml/min for 15min with the sample tube held at 40°C in a water bath. Trapped VHCs were extracted from the graphite carbon absorbent with 5ml of hexane by shaking for 20 seconds. The extract was analyzed by gas-liquid chromatography with an electron capture detector using a DB-624 column (0.32min i. d.×30m).
Quantitation limit of the nine VHCs were as follows: chloroform 2ppb; bromodichloromethane 0.2ppb; dibromochloromethane 0.2ppb; bromoform 0.5ppb; 1, 1, 1-trichloroethane 2ppb; 1, 1, 2-trichloroethane 3ppb; 1, 1, 2, 2-tetrachloroethane 0.5ppb; trichloroethylene 0.2ppb; tetrachloroethylene 0.2ppb. The recoveries of VHCs added to five kinds of food samples were 70.0-99.5%. Using the proposed method, 25 samples of commercial products were analyzed. Four VHCs were detected as follows: chloroform ND (below quantitation limit) -45.3ppb, bromodichloromethane ND-20.3ppb, dibromochloromethane ND-3.7ppb, 1, 1, 1-trichloroethane ND-2.7ppb. Bromoform, 1, 1, 2-trichloroethane, 1, 1, 2, 2-tetrachloroethane, trichloroethylene and tetrachloroethylene were not detected.