Data Series 233
U.S. GEOLOGICAL SURVEY
Data Series 233
Three types of quality-control samples were used in this study: blanks, spikes, and replicates. Blanks and spikes are used to estimate result bias, and replicates are used to estimate result variability. Additionally, surrogate compounds were added to VOC, PAH, and pesticide samples at the laboratory to monitor sample-specific performance of the analytical method.
Blanks are intended to be free of the analytes of interest and can be prepared in the laboratory or field. Blank samples are analyzed to test for bias that could result from contamination of environmental samples by the analytes of interest or by interfering compounds during any stage of sample collection, processing, or analysis. For this study, blanks for water samples were collected by processing USGS laboratory certified reagent water, known to be free of the analytes of interest, through all parts of the sample-collection process. Field blanks were collected at an environmental sampling location by passing the blank water through all field-cleaned sampling equipment. Field blanks were used to demonstrate that all stages of sample collection and processing did not introduce measurable contamination. Equipment blanks were collected annually to monitor for potential contamination due to sample collection and processing equipment. Source-solution blanks were collected to verify that the laboratory certified reagent water was free of the analytes of interest. Travel (trip) blanks were used to identify contamination that could occur during sample transport and analysis rather than as a result of sample collection and processing. Lot blanks were analyzed at the laboratory to test the cleanliness of the cartridges. Laboratory blanks (water and air methods) were used to demonstrate that the laboratory sample processing steps did not introduce measurable contamination.
Spiked samples are prepared by fortifying reagent water, an environmental water sample, or the air sampling media, with a known concentration of selected analytes. For this study, spiked samples were used to measure bias in analyte recovery. Matrix spikes also were used to test the effects of various sampled matrices on the recovery of specific compounds, including matrix interference or matrix-induced analyte degradation. One field water sample was spiked, in replicate, for pesticides during this study period.
Replicate water samples were collected and processed identically to the environmental sample and used to measure the variability during sample processing and analysis.
One field quality-control sample was collected during every sampling campaign except during September 2001. The type of quality-control sample collected and the sampling location were chosen randomly. The blank and replicate sample quality-control data for VOCs in water samples are given in table 14. The field-matrix spike and spike replicate quality control data for pesticides in water samples are given in table 15.
The quality of analytical results was monitored by adding surrogate compounds to each sample before it was processed for analysis. These surrogate compounds were added at the NWQL to monitor sample preparation and analysis. For water samples, 1,2-dichloroethane-d4, toluene-d8, and 1,4-bromofluorobenzene were added to each VOC sample, and diazinon-d10 and a-HCH-d6 were added to each pesticide sample. Surrogate results, in percent recovery, for each type of water sample is given in tables 3 and 4, respectively.
Each VOC air sample collected has an associated cartridge travel blank, cartridge (reagent) spike, cartridge lot blank, and laboratory blank that were analyzed along with the environmental sample. The quality-control data for chlorofluorocarbons and other compounds with low breakthrough volumes are given in tables 16A, 16B, 16C, and 16D, respectively. The quality-control data for the remaining 80 VOCs are given in tables 17A, 17B, 17C, and 17D, respectively.
Air samples for semivolatile organic compounds comprise three components (a GFF and a top and a bottom PUF plug) that were individually extracted. These extracts were analyzed by three distinct GC/MS procedures at the NWQL for PAHs and pesticides. Each air sample component was fortified with surrogate compounds at the NWQL to monitor sample preparation and analysis. Recovery data for surrogate compounds nitrobenzene-d5, 2-fluorobiphenyl, and terphenyl-d14 used to monitor performance for the PAH analysis are given in table 6. Recovery data for surrogate compounds diazinon-d10 and a-HCH-d6 used to monitor performance for the pesticides analyses by modified Schedules 2001 and 2002 are given in tables 7B and 7C, respectively.
The laboratory reagent blank and laboratory reagent spike results for PAHs are given in tables 18A and 18B, respectively. Corresponding laboratory blank and laboratory spike results for air sample analysis are in tables 19A and 19B using modified schedule 2001-type pesticides, and in tables 20A and 20B for modified schedule 2002-type pesticides.
The laboratory blank quality-control data associated with the second special study with the SPMD samples are given in table 21. The laboratory spike and laboratory blank quality-control data for the sixth (last) special study of wastewater compounds are given in table 22.
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Department of the Interior | U.S. Geological Survey
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