Ruberu Shiyamalie R, Liu Yun-Gang, Perera S Kusum
California Department of Public Health, Sanitation and Radiation Laboratories Branch, Richmond, CA 94804-6403, USA.
Health Phys. 2008 Oct;95(4):397-406. doi: 10.1097/01.HP.0000318890.23635.f4.
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.
本研究评估了一种液体闪烁计数（LSC）方法，该方法在检测饮用水中的总α活度方面比美国环境保护局（EPA）的气体正比计数（GPC）方法900.0具有多个优势。这里描述的改进方法涉及使用硝基甲烷作为猝灭剂来确定计数效率和溢出因子，并且它将样品制备减到最少。该方法的优点是在短计数时间（100分钟）和小样品等分试样量的情况下达到111 mBq L⁻¹的监管检测限。通过测试总溶解固体（TDS）范围从0.3 mg L⁻¹到1000 mg L⁻¹的现场样品，并将每种基质的加标量从194 mBq L⁻¹增加到11.6 Bq L⁻¹，进行了全面的方法验证研究。在所测试的两种LSC仪器（珀金埃尔默Quantulus 1220和帕卡德2550）上观察到了可比的方法精密度和准确度，前者表现更好。所呈现的数据表明，与常规GPC方法的500 mg L⁻¹限值相比，这种高效且高通量的LSC方法适用于TDS超过1000 mg L⁻¹的地下水样品。对加利福尼亚州各地的地下水井进行了采样，使用EPA批准的方法和改进的LSC方法分析了总α活度，并对结果进行了比较。
