TIMS(Triton)测定质量范围的扩展及其在溴同位素测定中的应用  

Extension of Mass Range and Application in the Determination of Bromine Isotope by TIMS(Triton)

作　　者：马云麒[1,2] 彭章旷 韩凤清[1] 刘文贵[4] 杨剑[1,3] 肖应凯[1] 张艳灵[1] 

机构地区：[1]中国科学院青海盐湖研究所盐湖地质与环境实验室,青海西宁810008 [2]中国科学院青海盐湖研究所盐湖化学分析测试中心,青海西宁810008 [3]中国科学院大学,北京100049 [4]中国地质大学,湖北武汉430074

出　　处：《质谱学报》2016年第5期465-470,共6页Journal of Chinese Mass Spectrometry Society

基　　金：国家自然科学基金项目(41173019;41473117);中国科学院仪器设备功能开发技术创新项目(2016G106);中国科学院关键技术人才项目(2015)资助

摘　　要：稳定溴同位素可用来识别和评价地下水的来源、成因及其形成的水文地球化学与物理过程。由于热电离质谱仪Triton的加速电压是固定10kV不可调节的,因此,其最大的测定质量数为310u。为了测定质量数更高的Cs2Br^+(m/z345,347)离子,本研究通过对热电离质谱仪Triton加速电压单元的改造,成功地将加速电压由10kV降低到8kV,使可测定的离子质量数从310u扩展到350u。在此基础上,建立了在8kV加速电压下相应的质量校正曲线,进行了基于133 Cs279 Br^+(m/z 345)和133 Cs281Br^+(m/z347)离子的稳定溴同位素静态多接收测量。结果表明:当溴含量低于10μg时,测定结果偏低;当溴含量高于10μg时,测定结果正常。该方法测定溴同位素具有涂样量少(10~20μg Br),测定外精度高(0.09‰~0.18‰)和采集数据时间短(8min可采集100个数据)等优点,可为地质样品中溴同位素地球化学的研究提供参考。Stable bromine isotope has impor tant significance in the ident if icat ion and evaluation of the source, cause, formation of groundwater and its hydrogeochemical and physical processes. Because the accelerating voltage of positive thermal ionization mass spectrometer （P-TIMS） （Triton） is not adjustable （10 kV）,its maximum measured mass is 310 u. In order to determine heavier ions, the power unit of the TIMS （Triton） was modified, and the acceleration voltage was reduced from 10 kV to 8 kV, then the mass range of the instrument was expanded from 310 u to 350 u. The mass calibration curve was established on 8 kV, and the stable isotope Cs2 Br＋ （m/z 345 , 347） were suc-cessfully measured. The ion beams of 133Cs2 79 Br＋ {m/z 345） and 133Cs281B r＋ （m/z 347） were simultaneously collected using Faraday central cup and Hi cup with reducing accel-erating voltage to 8 kV by a special accelerating voltage transformation. The results show that the 79 Br/81Br ratio is lower when the bromine content is lower than 10 jLtg, and the results are in agreement with previous reports when the bromine content is more than 10 jj.g. The static multicol lection me thod has many adva ntages , suchas , high precision （external accuracy lies 0. 09‰ -0. 18‰ ） ,small amount of sample loading （1 0 -20 μ.g Br ） and short acquisit ion time （just 8 min for 100 cycles）. Determinat ion of stable bromine isotopic ratios is achieved by thermal ionization mass spectrometer Triton with 8 kV accelerating voltage using static multicollection of Cs2Br＋ ions, which provids the possibility for the high precision determination of bromine isotope and also created the conditions for the study of Br isotopic geochemistry of geological samples.

关 键 词：正热电离质谱(P-TIMS) 加速电压改造 溴同位素 静态多接收 

分 类 号：O657.63[理学—分析化学]