Application Research Of Laser Ablation Inductively Coupled Plasma Mass Spectrometry In In-situ Microanalysis Of Minerals

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a powerful in-situ microanalysis tool for trace elements. Advantages of this technique include a high sensitivity and spatial resolution, low detection limits, rapid and simultaneous multi-element and isotope ratio determined. It can directly analyze the solid samples and it's the most promising in-situ microanalysis techniques for minerals. Quantitative calibration and elemental fractionation effect are the two major factors affecting the accuracy and precision of analytical results by LA-ICP-MS. Lack of reference materials and matrix effect between standards and samples have been the biggest challenges for quantitative calibration.In this paper, RSD of elemental relative sensitivity factors which were obtained from different reference materials were used to characterize the magnitude of differences of matrix effect. Differences of matrix effects between silicate glass and silicate mineral reference materials were evaluated systematically. The effectiveness of different internal standard elements to compensate for matrix changes were compared and influences of element fractionation effect were discussed. The results indicated that, compared with synthetic glass reference materials, the differences of matrix effect between glass reference materials with natural geological matrix and basalt matrix and silicate minerals were smaller with the RSDs of relative sensitivity factor of major and minor elements nearly within 7%. Ca was an ideal internal standard for analyzing silicate mineral samples. Because of slight fractionation behavior, Si was not an ideal internal standard element. The same elements in silicate glass reference materials and minerals had similar fractionation behaviors and the fractionation effects were unapparent, except for some elements which might contribute to the matrix effect. Satisfactorily quantitative analytical results of silicate minerals were obtained by external standard with natural geological glass reference materials normalized to Ca.Sulfide minerals have significant economic value because lots of transition metal and noble metal elements are highly enriched in sulfides. Measurement of content and distribution of trace elements in sulfide minerals plays an important role in geology and other research fields. Development of trace metal analysis in sulfide minerals by LA-ICP-MS has been hampered by the different ablation characteristics and more interference of sulfides from silicates and oxides, and especially by the extreme lack of reference materials of sulfides.A new strategy for analysis of sulfides by LA-ICP-MS was tested and established. This strategy made use of he relative sensitivity factor of Ca relative to S in anhydrite mineral reference material as a transition bridge, so that the and relative sensitivity factors of interesting elements in glass reference materials relative to Ca could be converted into relative sensitivity factors relative to S, thus enabling a joint calibration procedure of S internal standardization combined with matrix norimalization in the analysis of sulfide minerals.20 elements in the American polymetal sulfide mineral reference material MASS-1 were analyzed by this new method with multi-external standards. The relative errors of major elements in MASS-1 were less than 10% and the results of trace elements were nearly within given value ± uncertainty. 12 sulfide single minerals were also analyzed by using this new method. The relative errors of most major elements were less than 10% and the trace elements results agreed well with the calibrated results by MASS-1. In the case of serious lack of sulfide reference materials, this method could provide a new way of quantitative calibration for sulfides and more suitable for analysis of trace elements in sulfide minerals.