Detection of petroleum-contaminated soils using EQUILIBRIUM HEADSPACE and METHANOL EXTRACTION

Introduction Petroleum spills and leaking underground storage tanks comprise a significant portion of remediation projects. Soil removal and disposal is determined based on the contaminants and concentrations present. Specific target analytes are associated with this type of contamination. A number of these compounds are classified as volatile organics and are used to assess the severity of the contamination, whether remediation is required, and if necessary, the mode of disposal. The analytical technique used must accurately identify these components over a wide range of concentrations. Volatile organic compounds in soils can be determined using the analytical EPA Method 8260, “Volatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS).”(1) GC/MS adds another dimension to the analysis helping to ensure positive identification. There are a number of methods that can be used to extract volatile organics from soil samples. EPA method 5035 is a purge-and-trap technique for the determination of low-level volatile organic compounds (VOCs) in soils. EPA method 5030 is a purge-and-trap technique for the analysis of high concentration VOCs in soils using methanol(MeOH) extracts. EPA method 5021 is a general purpose method for the determination of VOCs in soils using equilibrium headspace. Method 5021 is not restricted by the concentration limitations imposed on the two purge-and-trap methods. Methanol extraction is a technique used in the analysis of VOCs. “...MeOH extraction can be a far more robust method of recovering VOCs from soil, especially for analytes with high octanol-water partitioning coefficients and matrices with organic carbon, than methods relying solely on vapor partitioning.”(2) However, this extraction technique introduces a dilution factor, which can affect the ability to detect the analytes of interest. This application brief demonstrates the effective use of methanol extraction, equilibrium headspace sample introduction, and mass spectrometry detection for lowlevel VOC determinations.