South Dakota Water Science Center
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Study Design and Analytical Results Used to Evaluate a Surface-Water Point Sampler for Volatile Organic CompoundsMichael J. Halde, Gregory C. Delzer, and John S. Zogorski
U.S. Geological Survey, 1608 Mountain View Rd., Rapid City, South Dakota 57702, USA
Phone (605) 355-4560, ext. 265, Telecopier, (605) 355-4523, mjhalde@USGS.gov
The most common technique used to sample streams for volatile organic compounds (VOCs) is manually dipping volatile organic analysis (VOA) vials by hand midstream. This technique does not assure that samples are collected in a consistent manner. A point sampler was designed to collect samples for the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program in surface water in a uniform and consistent manner nationwide. This report documents the study design used to evaluate the VOC point sampler, as well as comparative data from glass-siphoning and hand-dipping methods used in the laboratory and field. Quality-control data collected during the evaluation, specifically source-solution blanks, canister blanks, equipment blanks, and field blanks, are also presented.
The study found that the VOC point sampler collects samples in a representative manner, as compared to the glass-siphoning and hand-dipping methods. The relative standard deviation for replicate samples collected by the VOC point sampler was less than 10 percent for 57 of 73 VOCs indicating a high degree of sample reproducibility. Analyte loss was found to be neglibible based on a comparison of laboratory data because what spiked in the reservoir agrees with what was recovered. Furthermore, the cleaning protocol was found to be effective in eliminating any contamination of water samples from the point sampler.