title: Semi-quantitative analysis of contaminants in soils by direct analysis in real time (DART) mass spectrometry.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, Environmental Sciences Division, 944 E. Harmon Ave., Las Vegas, NV 89119, USA. grange.andrew@epa.gov
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Grange