SIMS含铀微粒同位素比分析中多原子离子影响及消除方法研究

Study on Effect and Solving Method of Polyatomic Ion in Isotopic Ratio Analysis of Uranium Bearing Particle in SIMS

实际环境样品基体成分十分复杂,多原子离子对二次离子质谱(SIMS)单微粒铀同位素比分析的影响不可忽略。本文实验分析了Pb、Ni、Zn、Si的多原子离子在SIMS单微粒铀同位素比分析中的干扰,并分别采用提高质量分辨率以及根据核素离子强度扣除其多原子离子的方法对结果进行校正。结果表明:Pb和Ni的多原子离子会影响含铀微粒次同位素比的测量,对铀主同位素比的影响可忽略;Zn和Si的多原子离子对铀主、次同位素比测量均基本无影响。将质量分辨率提高至800,能完全消除Ni多原子离子的影响,Ni-CRM U030混合(Ni粉混合CRM U030)微粒^(234)U/^(238)U同位素比测量值与参考值之间的相对偏差基本好于5%,^(236)U/^(238)U同位素比测量值与参考值之间的相对偏差基本好于15%;Pb多原子离子干扰无法通过提高质量分辨率进行消除,根据Pb离子强度扣除其多原子离子后,Pb-CRM U030混合微粒的^(234)U/^(238)U同位素比测量值与参考值之间的相对偏差基本好于10%,^(236)U/^(238)U同位素比测量值与参考值之间的相对偏差基本好于50%。将以上消除干扰的方法应用于真实样品分析,结果表明,其有效消除了多原子离子带来的干扰。

The matrix composition of the actual environmental samples is very complex,and the effect of polyatomic ion on the uranium isotope ratio analysis of SIMS individual particle cannot be ignored.The effects of polyatomic ion of Pb,Ni,Zn and Si on the uranium isotope ratio analysis of SIMS individual particle were analyzed in the experiment,and the results were corrected by improving the mass resolution,or subtracting the polyatomic ion according to the ion intensity of the nuclide.The results show that the polyatomic ion of Pb and Ni can affect the minor isotopic ratio analysis of uranium bearing particles,and the effect on the major isotopic ratio analysis can be ignored.The polyatomic ion of Zn and Si has no effect on the measurement of uranium major and minor isotope ratios basically.After increasing mass resolution to 800,the effect of polyatomic ion of Ni can be completely eliminated.For Ni-CRM U030 mixture particles,the measurement error of 234 U/238 U is better than 5%basically,and that of 236 U/238 U is better than 15%basically.The effect of polyatomic ion of Pb cannot be eliminated by increasing mass resolution.After deducting its polyatomic ion according to the intensity of Pb+,for Pb-CRM U030 mixture particles,the measurement error of 234 U/238 U is better than 10%basically,and the measurement error of 236 U/238 U is better than 50%basically.The method was applied to real sample analysis,and the results show that the effect caused by polyatomic ion is effectively eliminated.