Application of portable gas chromatography–mass spectrometer for rapid field based determination of TCE in soil vapour and groundwater

Abstract

The application of portable chromatography–mass spectrometer (GC–MS) is restrained by its detection limits without the development of proper sample pre-concentration methods. The primary focus of this paper is to introduce a practical field measurement methodology for the analysis of volatile organic compounds (VOCs) in soil vapour and groundwater using a portable gas (GC–MS)system for application to in situ assessment of vapour intrusion from VOC contamination. A solid-phase micro-extraction (SPME) technique was applied for sample pre-concentration before the GC–MS​ measurement. Practical in-field soil gas SPME sampling methods have been developed to optimise the SPME extraction efficiency to then ultimately improve the detection limits of portable GC–MS. An Australian site impacted by a chlorinated VOC, trichloroethylene (TCE), was the subject of the case study. To rapidly assess soil vapour samples in subsurface soil, in-house-developed retractable soil vapour sampling probes (SVSPs) were installed at the site in clusters at depths of 1 m, 2 m and 3 m below ground level at each sampling location. Use of the SVSPs for sampling enabled the generation of a three-dimensional map and distribution contours for TCE concentrations using the in situ measurement results of a portable GC–MS analysis for vapour intrusion investigation. The results of the portable GC–MS​ analysis were compared with the results from conventional USEPA methods, such as TO-15 and Method 8265 for soil vapour and groundwater samples, respectively. This work demonstrates that the developed methodology of using a portable GC–MS system has the capability for in-field quantitative analysis of VOCs for rapid contaminated site vapour intrusion assessment.