EVALUATION OF AN IN-SITU, ONLINE PURGING SYSTEM FOR THE CONE PENETROMETER

Materials that will be used to construct an in situ, on-line purging s ystem for the cone penetrometer were evaluated. Transfer efficiencies for volatile organic compounds (VOCs) through stainless steel, nickel, aluminum, and Teflon(R) tubings were determined using a gas-phase mix ture of VOCs containing trichloromethane, tetrachloromethane, 1,1,1-tr ichloroethane, tetrachloroethene, hexane, benzene, toluene, and 1,2-di methylbenzene. The water content of the gas stream had an insignifican t effect on the quantitative transfer of VOCs through Teflon(R) tubing but was critical to efficiently transfer the compounds through metal tubing, particularly nickel. Transfer efficiencies for all eight analy tes in moist gas streams through stainless steel were greater than 95% . Toluene, tetrachloroethene, and 1,2-dimethylbenzene were transferred with 93%, 81%, and 80% efficiency, respectively, when they were drawn through Teflon(R) PFA (perfluoroalkoxy) tubing. In general, the reten tion of the VOCs by Teflon(R) increases with decreasing aqueous solubi lity of the analyte. The efficiencies at which VOCs were purged from a queous standards in Teflon(R) PFA, Type 304 stainless steel, and glass vessels were similar. Stainless steel was superior to nickel, aluminu m, and the Teflon(R) polymers as a material for an in situ, on-line pu rging system for the cone penetrometer.