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R9 Laboratory SOP 305
Volatile Organics Analysis
Summary
The function of the Region 9 Volatile Organics laboratory is to analyze water, soil and sediment samples for volatile organic compounds in support of the EPA's Superfund, RCRA, WQM, NPDES, UIC, and Drinking Water programs. The applicability of these procedures to specific project data quality objectives must be assessed on a case by case basis. The QC criteria specified in the procedures do not meet compliance criteria for either drinking water or NPDES monitoring projects.
This Standard Operating Procedure (SOP) describes the procedures used for the analysis of volatile organic compounds in the Region 9 Laboratory. Volatile organic compounds are purged from water samples in a fritted sparge cell. Low level water samples use a 25 mL sample volume. Low level soil samples are purged by adding a 5-mL aliquot of water to 5 grams of the sample, and purging with a needle sparger while heating to 40°C. Medium level soil samples are extracted in methanol and an aliquot of the extract is purged out of 5 mL of water. An inert gas (helium) is bubbled through the sample in the sparge cell, which causes the purgeable volatile organics to be transferred from the aqueous phase to the vapor phase. The vapor phase is swept through a column, or trap, containing a sorbent material at ambient temperature, where the volatile organics are trapped. After the purging of the sample is completed, the sorbent trap is heated and back flushed with helium which desorbs the volatile organics onto a capillary column in a gas chromatograph (GC). The GC is temperature programmed, which separates the volatile organic compounds. They are then introduced into, and detected by, a mass spectrometer (MS).
The samples are spiked with internal standards (IS) and system monitoring compounds (SMC) before they are purged. The target volatile organic compounds and system monitoring compounds are identified in the sample by analyzing standards under the exact same conditions employed for samples, and comparing the resulting mass spectra and GC retention times. A response factor is established for each target and system monitoring compound during the initial and continuing calibrations by comparing the MS response of the primary ion produced by the target and system monitoring compounds to the MS response for the primary ion produced by the associated internal standard. Each target and system monitoring compound is quantitated by comparing the responses of the target and system monitoring compound responses to the internal standard responses, using the response factors from the most recent continuing calibration.
Non-target compounds are identified by comparing the resulting mass spectra of the non-target compound to the mass spectra contained in the National Institute of Standards and Technology (NIST) Library in the MS database. An estimated quantitation is performed for the non-target compounds by comparing the total MS response to the nearest internal standard total MS response, assuming a response factor of 1.0.