SOLID SORBENT METHOD FOR THE COLLECTION AND ANALYSIS OF VOLATILE HALOGENATED ORGANIC-COMPOUNDS IN SOIL-GAS

A solid sorbent technique was developed to measure volatile halogenate d organic compounds (VHOCs) in soil gas. The VHOCs were preconcentrate d onto graphitized carbon black (Carbotrap) and analyzed by thermal de sorption/high-resolution gas chromatography with electron-capture dete ction. The method detection limit (MDL) for trichloromethane (CHCl3) a nd tetrachloromethane (CCl4) in soil gas was approximately 1 mu g m(-3 ) for a 60-ml sample volume. A thermal-desorption temperature of 200 d egrees C was sufficient to recover more than 90% of the VHOCs from the sorbent. Breakthrough volumes for CHCl3 and CCl4 were at least 1000 m l when soil gas was drawn through the sample cartridge at a rate of 30 ml min(-1). Sorbent cartridges stored at 20 degrees C were sufficient ly stable for at least 30 days. Application of the method in the field indicated that the measured concentration of VHOCs in soil-gas monito ring wells was sensitive to the volume of soil gas that was withdrawn.