The methodology study of trace element in-situ analyses using Laser Ablation Inductively Coupled Plasma Mass Spectrometer

Abstract

National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 610, 612, 614 glasses have been measured by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The experiments are designed elaborately to optimal UV laser probe (266 nm) and ICP-MS operating conditions. The measurement results of 78 experiments of 25 groups in 5 days show that 30 trace elements in NIST612 have the statistic precision of about 4% when the 44Ca was chosen as internal standard, meanwhile those elements of same NIST612 standard glass have the statistic precision of about 6% when the 29Si was chosen as the internal standard. Good measurement accuracy of less than 10% which compared with certified data can also be acquired routinely when we measure the NIST610, NIST612 and NIST614 glasses using the NIST612 as the calibration reference material. The total relative statistic deviation of measurement can be deduced by two individual test statistic deviations. Choosing NIST612 as calibration reference material, we get total relative statistic deviation value of less than 10% of most trace elements both in NIST610 (450μg/g) and in NIST612 (40μg/g) when we choose 44Ca as internal standard. By the contrast, we can get the total relative statistic deviation value of 15% to most of trace elements in NIST612 if we choose 29Si as internal standard. It suggests that 44Ca is better than 29Si as the internal standard mass. Except to Ni, Sc, Rb, Zr, Sm, Gd and Pb, that most of trace elements have the total relative statistic deviation value of less than 20% in NIST614 (0.8μg/g) which is a little higher than in NIST610 and NIST612 show that the measurement precision will deteriorate with the decreasing of concentration of measured element. High blank accounts for the bad Sc value and the interference of CaO may account for the bad Ni value. The bad precision of Rb, Zr, Sm, Gd and Pb may result from the memory effect of whole system which will be displayed more obviously when we analysis the low concentration elements.

利用 2 6 6 nm紫外激光熔融電感藕合等離子體質譜儀 ,在最優化測試條件下 ,對標準玻璃樣品 NIST6 12中的 30個微量元素進行了 5天 2 5組 78次的測定。在采用最小二乘法擬合后 ,選用 44 Ca為內標計算的數據精密度為 4%左右 ;選用 2 9Si為內標計算的數據精密度為 6 %左右。以 NIST6 12為外標 ,以 44 Ca和 2 9Si為內標 ,分別測定微量元素濃度為 45 0μg/g左右的NIST6 10 ,40μg/g左右的 NIST6 12以及微量元素濃度小于 1μg/g的 NIST6 14標準玻璃樣品 ,與標樣的標定值比較 ,數據的準確度絕大部分小于 10 %。以 NIST6 12為外標 ,選用 44 Ca為內標 ,根據測定 NIST6 12和 NIST6 10的數據的精密度推導 ,激光探針電感藕合等離子體質譜法測定濃度為 45 0 μg/g左右的微量元素時 ,數據的精密度小于 10 % ;測定濃度為 40 μg/g左右的微量元素時 ,大部分元素的數據精密度也在 10 %以下 ;以 NIST6 12為外標 ,選用 2 9Si為內標 ,根據測定 NIST6 12和 NIST614的数据的精密度推导, 激光探针电感藕合等离子体质谱法测定浓度为40μg/g左右的微量元素时, 绝大部分元素的数据的精密度小于15%; 测定浓度大约在0. 8μg/g左右的微量元素时, 除Ni, Sc, Rb, Zr , Sm , Gd, Pb 七个元素的精密度较差外, 其余23个元素的数据精密度在20%以下。空白背景值较高是导致Sc 精密度差的主要原因, Ni 元素精密度差可解释为较高的空白背景和CaO 干扰的综合结果。Rb, Zr, Sm , Gd, Pb 五元素在低浓度时数据精密度急剧变差的原因可能与这几个元素的记忆效应有关。