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National Water Quality Laboratory

Friday December 15, 2017

U.S. GEOLOGICAL SURVEY Open-File Report 95-719

Methods of Analysis by the U.S. Geological Survey National Water Quality Laboratory - Determination of Semivolatile Organic Compounds in Bottom Sediment by Solvent Extraction, Gel Permeation Chromatographic Fractionation, and Capillary-Column Gas Chromatography/Mass Spectrometry

By Edward T. Furlong, Deborah G. Vaught, Leslie M. Merten, William T. Foreman, and Paul M. Gates

A method for the determination of 79 semivolatile organic compounds (SOCs) and 4 surrogate compounds in soils and bottom sediment is described. The SOCs are extracted from bottom sediment by solvent extraction, followed by partial isolation using high-performance gel permeation chromatography (GPC). The SOCs then are qualitatively identified and quantitative concentrations determined by capillary-column gas chromatography/mass spectrometry (GC/MS). This method is designed for simultaneous isolation of organochlorine (OC) pesticides, including toxaphene and polychlorinated biphenyls (PCBs). When OCs and PCBs are determined, an additional alumina-over-silica column chromatography step follows GPC cleanup, and quantitation is by dual capillarycolumn gas chromatography with electron-capture detection (GC/ECD).

Bottom-sediment samples are centrifuged to remove excess water and extracted overnight with dichloromethane. The extract is concentrated, centrifuged, and then filtered through a 0.2-micrometer polytetrafluoroethylene syringe filter. Two aliquots of the sample extract then are quantitatively injected onto two polystyrene-divinylbenzene GPC columns connected in series. The SOCs are eluted with dichloromethane, a fraction containing the SOCs is collected, and some coextracted interferences, including elemental sulfur, are separated and discarded. The SOC-containing GPC fraction then is analyzed by GC/MS. When desired, a second aliquot is further processed for OCs and PCBs by combined alumina-over-silica column chromatography. The two fractions produced in this cleanup then are analyzed by GC/ECD.

At a spike concentration of 800 micrograms per kilogram (µg/kg), recoveries ranged from 17.9 to 117.3 percent, with a mean recovery of 77.4 percent. At a spike concentration of 2,000 µg/kg, recoveries ranged from 1.3 to 106.4 percent, with a mean percent recovery of 61.4 percent. The corresponding variation in recoveries is reflected in both the standard deviations for individual SOCs and the standard deviation of recovery for all SOCs. These standard deviations average 13.2 percent and ranged from 1.6 to 33.9 percent for individual SOCs spiked at 800 µg/kg. Standard deviations average 5.2 percent and ranged from 1.6 to 33.9 percent for individual SOCs spiked at 2,000 µg/kg. This report fully describes and is limited to the determination of SOCs by GC/MS .

VIEW the report. (pdf)


 

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