岩石和矿物中氧同位素组成分析制样装置改进及分析方法

对五氟化溴法氧同位素组成样品制备装置进行改进并对分析方法进行优化。改进的样品制备装置包含12个镍反应器,可完成12件氧同位素样品制备,提高了制备效率;采用O 2作为工作气体对样品中的氧同位素组成进行测定,避免了向CO 2转化过程中潜在的氧同位素分馏,还可同时获取δ18 O与δ17 O值;通过5A分子筛直接对O 2进行吸附,提高了收集效率;采用电容真空规对提取的O 2进行产率测量,确定了制样装置中石英单矿物质量与O 2压强之间的线性关系。以国家标准物质GBW 04409、石英单矿物以及花岗岩地质样品为参考,在改进的装置上进行氧同位素样品制备分析,其分析精度分别为0.09‰、0.09‰和0.10‰,均优于0.2‰,标准物质δ18 O VSMOW的测量平均值为11.09‰,在误差范围内与标准值11.11‰相吻合。样品制备效率及分析结果表明:改进的氧同位素样品制备装置及分析方法测量结果准确。

Improvement of analysis device and method of oxygen isotopic compositions in rocks and minerals

Based on the traditional analysis method and sample preparation device of oxygen isotopic compositions by BrF 5,some improvement has been made to optimize the analysis method and the sample preparation device.The improved sample preparation device includes 12 nickel reactors which has enhanced the preparation efficiency.O 2 is used as working gas to determine the oxygen isotopic compositions of the samples,that not only avoids possible isotope fractionation during the conversion of O 2 to CO 2,but also obtainsδ18 O andδ17 O values simultaneously.Due to the use of 5A molecular sieves to absorb O 2,the collection efficiency is improved.Capacitance diaphragm vacuum gauge is used to measure the yield of O 2,and the linear relationship between the mass of quartz and the pressure of O 2 in the preparation device is determined.The national standard material GBW04409,quartz and granite samples were used as reference to test the improved device for preparation and analysis of oxygen isotopic compositions.The analytical accuracy is 0.09‰,0.09‰and 0.10‰,respectively,which are less than 0.2‰.The average value of the standard material is 11.09‰,which is in good agreement with the recommended data 11.11‰.The preparation efficiency,analytical accuracy and value of standard material suggested that the improved preparation device and method is suitable for the analysis of oxygen isotopic compositions.