蒸馏法富集纯化Os实验条件研究及其在负离子热电离质谱测量中的应用

Study on the Conditions for Enrichment and Purification of Os by Micro-distillation and Its Application in NTIMS Measurements

微蒸馏是富集纯化Os的一项重要化学前处理技术,提高Os回收率对提高Os的负离子热电离质谱(NTIMS)测量精度尤为重要。在微蒸馏过程中,蒸馏温度、吸收液体积、蒸馏时间等对Os回收率具有重要影响,但目前微蒸馏的实验条件不够明确,导致Os回收率不稳定,影响NTIMS测量精度,易增加所得Re-Os年龄误差。本文以自制的含Os溶液为对象,以ICP-MS为测量手段,对微蒸馏过程中多种实验条件对Os回收率的影响进行深入研究,以期获得最佳微蒸馏实验条件,满足后续NTIMS对Os信号强度的测量要求。结果表明:在溶液蒸干温度为120℃并保持15 min,微蒸馏温度为80℃,氢溴酸吸收液体积为15μL,微蒸馏时间为2 h的条件下,获得Os回收率为80%~90%,能够满足多种地质样品尤其是中酸性岩浆岩、热液硫化物等pg级地质样品的NTIMS测量要求,在保证Os信号强度的情况下提高了分析效率。

BACKGROUND： Micro-distillation is an important chemical pretreatment technology for the enrichment and purification of Os. It is particularly important to improve Os recovery by optimizing the micro-distillation experimental conditions to ensure the accurate measurement of Os by NTIMS. The micro-distillation temperature,absorbing solution volume,and reaction time have significant influence on the recovery of Os. However,the optimum experimental conditions for micro-distillation are not clear,thus resulting in unstable Os recovery,affecting NTIMS measurement accuracy,and easily resulting in increased Re-Os dating error.OBJECTIVES： To evaluate the influence of different experimental conditions on the yield of Os during the microdistillation for improving the recovery of Os,ensuring the intensity and stability of the Os measurement signal by NTIMS.METHODS： A self-made Os-containing solution was chosen as the research object and ICP-MS was used as the measurement method. The element Ir was used as the internal standard to monitor the Os signal,and the Os recovery was calculated by the sample signal count.RESULTS： The results show that the maximum recovery of Os was obtained when the HBr solution was evaporated at 120℃ for 15 min,the micro-distillation temperature was 80℃,the HBr absorption solution was 15 μL,and the micro-distillation reaction time was 2 h. The Os recoveries were 80%-90% under the optimum experimental condition.CONCLUSIONS： Os recovery under the optimum micro-distillation experimental conditions satisfies the measurement requirements of NTIMS,especially for pg level geological samples. It also increases the Os signal intensity and improves the efficiency of experiments.