A Tube and Cartridge Method for Down‐Hole Sampling for Trace Organic Compounds in Ground Water

A small ground-water sampling device has been developed which extends the down-hole use of the adsorption/thermal desorption (ATD) analysis method for nonpolar organic compounds to very narrow piezometers (I.D. > 0.64 cm). The sampler consists of a sorbent cartridge, a flow restrictor, and a tube leading to the ground surface. The device is lowered down a piezometer, and water-column pressure forces the sample through the cartridge. In the laboratory, the water is removed from the cartridge and the sorbed compounds are thermally desorbed to a gas chromatography (GC) column for analysis. Since the analytes are sorbed on the cartridge down-hole, volatilization losses are avoided. Samples can be obtained without being influenced by the water column above the sampler or by tubing or pumps; many uncertainties associated with well purging and contamination from well casings and samplers can be minimized. The method was tested by sampling at a landfill. The coefficients of variation were in the 10-18% range at the low μg/1 level. The limits of detection for several compounds were all under 0.1 μg/1, some being less than 1 ng/1. Sorption efficiencies of >93% were found for a variety of compounds. The method will be attractive when sensitivity and freedom from volatilization losses and sampler-related contamination are required.

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