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This report presents precision and accuracy data for volatile organic compounds (VOCs) in the nanogram-per-liter range, including aromatic hydrocarbons, reformulated fuel components, and halogenated hydrocarbons using purge and trap capillary-column gas chromatography/mass spectrometry. One-hundred-four VOCs were initially tested. Of these, 86 are suitable for determination by this method. Selected data are provided for the 18 VOCs that were not included. This method also allows for the reporting of semiquantitative results for tentatively identified VOCs not included in the list of method compounds. Method detection limits, method performance data, preservation study results, and blank results are presented.The authors describe a procedure for reporting low-concentration detections at less than the reporting limit. The nondetection value (NDV) is introduced as a statistically defined reporting limit designed to limit false positives and false negatives to less than 1 percent. Nondetections of method compounds are reported as "less than NDV." Positive detections measured at less than NDV are reported as estimated concentrations to alert the data user to decreased confidence in accurate quantitation. Instructions are provided for analysts to report data at less than the reporting limits. This method can support the use of either method reporting limits that censor detections at lower concentrations or the use of NDVs as reporting limits. The data-reporting strategy for providing analytical results at less than the reporting limit is a result of the increased need to identify the presence or absence of environmental contaminants in water samples at increasingly lower concentrations.Long-term method detection limits (LTMDLs) for 86 selected compounds range from 0.013 to 2.452 micrograms per liter (ug/L) and differ from standard method detection limits (MDLs) in that the LTMDLs include the long-term variance of multiple instruments, multiple operators, and multiple calibrations over a longer time. For these reasons, LTMDLs are expected to be slightly higher than standard MDLs. Recoveries for all of the VOCs tested ranged from 36 (tert-butyl formate) to 155 percent (pentachlorobenzene). The majority of the compounds ranged from 85 to 115 percent recovery and had less than 5 percent relative standard deviation for concentrations spiked between 1 to 500 (o,g/L in volatile blank-, surface-, and ground-water samples. Recoveries of 60 set spikes at low concentrations ranged from 70 to 114 percent (1,2,3trimethylbenzene and acetone). Recovery data were collected over 6 months with multiple instruments, operators, and calibrations.In this method, volatile organic compounds are extracted from a water sample by actively purging with helium. The VOCs are collected onto a sorbent trap, thermally desorbed, separated by a Megabore gas chromatographic capillary column, and finally determined by a full-scan quadrupole mass spectrometer. Compound identification is confirmed by the gas chromatographic retention time and by the resulta...

A method for the determination of 30 individual organochlorine pesticides, total toxaphene, and total poly chlorinated biphenyls (PCBs) in aquatic bottom sediment is described and laboratory performance data are provided. The method was developed in support of the U.S. Geological Survey's National Water-Quality Assessment program and is based on conventional Soxhlet extraction using dichloromethane. Two aliquots of the sample extract are quantitatively injected onto a styrene-divinylbenzene gel permeation column and eluted with dichloromethane. This gel permeation chromatography step removes inorganic sulfur and large naturally occurring molecules from the sediment extract. The first aliquot is analyzed for semivolatile organic compounds by gas chromatography with mass spectrometric detection. The second aliquot is further split into two fractions by combined alumina/silica adsorption chromatography prior to determination of the organochlorine pesticides and PCBs by dual capillary-column gas chromatography with electron-capture detection (GC/ECD). This report completely describes and is limited to the determination of the organochlorine pesticides and PCBs by GC/ECD. Current (February 1995) data-reporting limits have been set at 1 to 5 micrograms per kilogram for 30 chlorinated pesticides, 50 micrograms per kilogram for total PCBs, and 200 micrograms per kilogram for toxaphene. SAFETY CONSIDERATIONS This method involves the handling of known, suspected, and possibly unknown hazardous chemicals and reagents. The method uses substantial volumes of dichloromethane, a suspected carcinogen, during sample extraction and some extract clean-up steps. The USEPA has special regulations covering the handling and disposal of PCBs. Carefully follow all standard safety practices regarding the use of solvents, compressed gases, OC pesticides, PCBs, polycyclic aromatic hydrocarbons, and other method-related chemicals. Consult material safety data sheets for additional safety information. Always wear appropriate protective clothing, gloves, and eye wear, and use adequate ventilation when preparing samples or standard solutions. Electron-capture detectors (ECDs) contain radioactive 63nickel and must not be opened by unlicensed operators. ANALYTICAL METHOD Organic Compounds and Parameter Codes: Organochlorine pesticides and gross polychlorinated biphenyls, bottom sediment, gas chromatography, O-5129-95 (see table 1)

This report presents the results of the U.S. Geological Survey's analytical evaluation program for six standard reference samples --T-173 (trace constituents), M-166 (major constituents), N-77 (nutrient constituents), N-78 (nutrient constituents), P-40 (low ionic-strength constituents), and Hg-36 (mercury) --that were distributed in March 2003 to laboratories enrolled in the U.S. Geological Survey sponsored interlaboratory testing program. Analytical data received from 110 laboratories were evaluated with respect to overall laboratory performance and relative laboratory performance for each analyte in the six reference samples. Results of these evaluations are presented in tabular form. Also presented are tables and graphs summarizing the analytical data provided by each laboratory for each analyte in the six standard reference samples. The most probable value for each analyte was determined using nonparametric statistics.

This Fact Sheet presents data for analysis ofnanogram-per-liter concentrations of methyl ten-butyl ether (MTBE) and three other ether gasoline oxygenates, including methyl tert-pentyl ether (TAME), diisopropyl ether (DIPE), and ethyl ten-butyl ether (ETBE), bypurgeand-trap capillary-column gas chromatography/mass spectrometry. Long-term method detection levels (LT-MDLs)for MTBE, TAME, DIPE, and ETBE ranged from 15 to 83 nanogramsper liter (0.015 to 0.083 microgram per liter). Nanogram-per-liter-concentration detections are reported if all of the identification criteria are met, whereas previous methods censored detections at a predetermined method reporting level. The reporting level for this method is defined as two times the LT-MDL, does not censor detections at less than this concentration, and is referred to as the nondetection value (NDV). Bias and variability data from multiple analyses, analysts, and instruments over a 60-day period show the oxygenate recoveries ranging from 100 to 109 percent, with 6 to 8 percent relative standard deviation. MTBE, TAME, DIPE, and ETBE were not detected in the analysis of 225 laboratory reagent blanks from January to December 1997. A preservation study in ground water and surface water indicates that all the oxygenates are stable atpH 2 for up to 216 days, with recoveries ranging from 94 to 115 percent on day 216, and relative standard deviations ranging from 5 to 9 percent for the duration of the study. A full description of this purge-and-trap method is available in Connor and others (1998).