Semi-quantitative analysis of contaminants in soils by direct analysis in real time (DART) mass spectrometry
A. H. Grange, U.S. Environmental Protection Agency, Office of Research and Development, Environmental Sciences Division, 944 E. Harmon Ave., Las Vegas, NV 89119, USA.
Cleaning up contaminated sites is a goal of the U.S. Environmental Protection Agency (EPA). A simple, high-throughput, inexpensive, selective, and specific screening method for semi-volatile, polar organic contaminants would provide high spatial resolution for monitoring remediation and for documenting successful clean ups in numerous Superfund, Brownfield, and other contaminated sites.
An autosampler/Direct Analysis in Real Time (DART)/time-of-flight (TOF) mass spectrometer, with or without a Vapur® evacuated flange, was used to analyze 0.01–33% levels of aspirin, diphenylamine, and pentachlorophenol mixed with soil. Triplicate water-soaked swabs were manually rotated in wet analyte:soil mixtures, air dried for 2–3 h, and analyzed directly. To minimize carryover, insensitive and sensitive instrumental conditions were used to analyze high and low analyte levels, respectively. Simulated two-dimensional (2D) mapping and remediation threshold experiments were performed to test the utility of DART-TOFMS for possible sampling strategies.
Analyte levels differing by factors of 10 were discernible. Data were acquired for 30 swabs in 0.9 min and 3 min with helium stream temperatures of 150 °C and 250 °C and swab transport velocities of 1.45 cm/s and 0.5 cm/s, respectively. With the Vapur flange attached, the average relative standard deviations (RSDs) (n = 3) were between 16% and 40% for different analytes and analyte levels. Carryover was greatly reduced by removing the Vapur flange, but higher RSDs and occasional plugging of the cone orifice were observed.
A rapid, simple, rugged, and relatively inexpensive, but selective and sufficiently sensitive, semi-quantitative screening method for semi-volatile, polar, organic compounds in soil was demonstrated. The technique would provide the high spatial resolution necessary to find localized areas of high contamination within contaminated sites that might pose a risk to human and ecological health. Published 2012. This article is a US Government work and is in the public domain in the USA.