title: An improved liquid scintillation counting method for the determination of gross alpha activity in groundwater wells.
abstract: A liquid scintillation counting (LSC) method having several advantages over the gas proportional counting (GPC) U.S. Environmental Protection Agency (EPA) Method 900.0 for the detection of gross alpha activity in drinking water was evaluated in this study. The improved method described here involves the use of nitromethane as the quench agent for establishing counting efficiencies and spillover factors, and it minimizes sample preparation. It has the advantage of achieving the regulatory detection limit of 111 mBq L(-1) with short count times (100 min) and small sample aliquot sizes. A thorough method validation study was performed by testing field samples ranging in total dissolved solids (TDS) from 0.3 mg L(-1) to 1,000 mg L(-1) and spiking each matrix from 194 mBq L(-1) to 11.6 Bq L(-1). Comparable method precision and accuracy was observed on the two types of LSC instruments tested, Perkin Elmer Quantulus 1220 and Packard 2550, with the former giving better performance. Data presented demonstrate that this efficient and high throughput LSC method is suitable for groundwater samples in excess of 1,000 mg L(-1) of TDS in contrast with the 500 mg L(-1) limit by the routine GPC method. Groundwater wells across the state of California were sampled, analyzed for gross alpha activity using the EPA- approved method and the improved LSC method, and the results were compared.
authors.affiliation: California Department of Public Health, Sanitation and Radiation Laboratories Branch, Richmond, CA 94804-6403, USA. sruberu@cdph.ca.gov
authors.forename: Shiyamalie R
authors.initials: SR
authors.lastname: Ruberu
authors.forename: Yun-Gang
authors.initials: YG
authors.lastname: Liu
authors.forename: S Kusum
authors.initials: SK
authors.lastname: Perera
mesh_terms: D000512:Alpha Particles; D002140:California; D011834:Radiation Monitoring / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results; D012588:Scintillation Counting / Q000295:instrumentation / Q000379:methods*; D012680:Sensitivity and Specificity; D014481:United States; D014484:United States Environmental Protection Agency; D014875:Water Pollutants, Radioactive / Q000032:analysis*; D014881:Water Supply / Q000032:analysis*
chemical_list: D014875:Water Pollutants, Radioactive