氧化-吹扫-金柱捕集-(双柱)热脱附-电感耦合等离子体质谱测定液体和固态样品中痕量汞同位素含量

Determination of Trace Mercury Isotopes in Liquid and Solid Samples by Inductively Coupled Plasma Mass Spectrometry with Oxidation,Purge-trap,Dual-stage Thermal Desorption

建立了液体和固态环境样品中痕量Hg同位素的氧化-吹扫-金柱捕集-热脱附-电感耦合等离子体质谱(ICP-MS)测定法。样品采用美国环保局(USEPA)1631方法预处理,气液分离降低基底干扰,金柱富集提高灵敏度;将Hg蒸气直接引入ICP-MS,利用ICP-MS的分辨能力,测定Hg同位素。198 Hg和201 Hg的检测限分别为0.07、0.11ng/L;土壤、沉积物和生物等固体样品中198 Hg和201 Hg的检测限分别为0.15、0.20ng/g。在最佳条件下,连续7次测定198 Hg和201 Hg基底加标水样,测定结果的相对标准偏差(RSD)均为7.0%,同位素比值(201 Hg/198 Hg)的内精度为0.26%(I RSD)。痕量198 Hg和201 Hg海水样基底加标回收率分别为98.3%～116.0%、92.4%～109.4%,生物样198 Hg和201 Hg的基底加标回收率分别为88.4%～106.7%、79.7%～88.0%。与标准参考溶液198 Hg和201 Hg的相对偏差分别为-0.15%、-0.09%。对于褶牡蛎的同位素组成分析,2次测定同位素比值(201 Hg/198 Hg)与自然界Hg同位素比理论值的相对偏差分别为0.4‰、-6.0‰。该方法成功用于标准参考样品和实际生物样品的同位素组成分析,并可成为Hg迁移和转化示踪实验的分析技术手段。

A method based on oxidation, purge-trap and dual- mercury（Hg） isotopes in （USEPA） Method 1631 inductively coupled plasma mass spectrometry（ICP-MS） coupling with -trap thermal desorption has been established for the determination of trace d and solid environmental samples. U. S. Environmental Protection Agency employed for sample pretreatment. Matrix interference was reduced with gas-liquid separation, ana sensitivity was improved with gold amalgamation.Hg vapor was directly introduced to ICP-MS after thermal desorption from the gold trap, and Hg isotopes were simultaneously determined. The detection limits of 19SHg and 201Hg were 0.07 ng/L and 0. 11 ng/L, respectively. For solid samples such as soil, sediment, and biota, the detection limits were 0. 15 ng/g and 0. 20 ng/g, respectively. Under the optimized conditions,the RSDs（n=7） of 198Hg and 201Hg were both 7.0% for a matrix spiked water sample,and the internal precision（I RSD） of Hg isotope ratios（201Hg/19SHg） was 0.26‰. The recoveries of matrix spiked seawater samples containing trace 198Hg and z01 Hg were 98.3% -116.0%, 92.4%-109.4%. The recoveries of 19, Hg and 201 Hg from matrix spiked biota samples were 88.4%-106. 7%, 79.7% 88. 0%. The determination result o{ a standard reference solution showed --0.15% relative deviation for 198Hg, and --0. 09% for 201Hg. For duplicate measurement of mercuy isotopes in Ostrea Plicatula Gmelin samples collected from ambient environment,the relative deviations for isotopic ratios（201Hg/198Hg） between measured and its theoretical value in nature were 0.4‰ and --6.0‰. The proposed method was successfully applied to determine Hg isotopic composition in stardard reference samples and practical biota samples, and was expected to be applied in tracing experiments for studying Hg transportation and transformation.