Development and preliminary evaluation of a cone penetrometer-based method forin situ determination of volatile organic compounds in groundwater

Abstract

We report the development of an in situ method for quantitatively determining complex mixtures of volatile organic compounds (VOCs) at low levels in groundwater formations. The method is based on the use of a novel in situ groundwater collection and sample purging device that is integrated into a cone penetrometer testing (CPT) push rod. This device, the QVAC (quantitative volatiles analysis for cone penetrometry), is used for quantitatively measuring complex mixtures of VOCs in groundwater at regulatory levels. A breadboard prototype QVAC probe made of stainless steel was tested in the laboratory to identify the optimal design parameters for a CPT-scale version. A full-scale prototype QVAC probe was integrated within a CPT push rod, with the use of miniature valves and a conductivity-based level sensor to accurately sample and purge a 5.0-ml groundwater sample. Following transfer of the VOCs through thermostated stainless-steel tubing to the sorbent trap at the surface, on-line thermal desorption/gas chromatography with mass spectrometric detection is performed. We report the design of the probe, optimization of the operational protocol, and the results of laboratory and initial field testing in which the precision, carryover, and calibration sensitivity were examined. © 1997 John Wiley & Sons, Inc.