A Non-Matrix-Matched Calibration Method for In Situ Major and Trace Element Analysis of Scheelite by Nanosecond LA-ICP-MS

Xijuan Tan; Honghao Tian; Lin Lu; Dongyang Xiong; Ting Liang

doi:10.3390/molecules29010051

A Non-Matrix-Matched Calibration Method for In Situ Major and Trace Element Analysis of Scheelite by Nanosecond LA-ICP-MS

Molecules. 2023 Dec 20;29(1):51. doi: 10.3390/molecules29010051.

Authors

Xijuan Tan¹, Honghao Tian¹, Lin Lu², Dongyang Xiong¹, Ting Liang¹

Affiliations

¹ Laboratory of Mineralization and Dynamics, College of Earth Sciences and Land Resources, Chang'an University, 126 Yanta Road, Xi'an 710054, China.
² Shaanxi Mineral Resources and Geological Survey, Shaanxi Institute of Geological Survey, Xi'an 710068, China.

Abstract

In this work, a reliable and robust in situ non-matrix-matched calibration method is proposed for element composition determination in scheelite samples. With external calibration against the silicate glass standard reference material NIST SRM 610, the concentrations of both major elements (Ca and W) and trace elements (Si, Fe, Mo, Y, rare earth elements, etc.) in scheelite are determined using an ArF 193 nm excimer nanosecond laser ablation-inductively coupled plasma mass spectrometer (LA-ICP-MS). Here, the ablation was performed by hole drilling under a helium (He) environment using a laser spot size of 35 μm and a laser repetition of 5 Hz, and the aerosols were then transported to a quadrupole ICP-MS by a mixture of He and make-up gas argon (Ar) with a total gas flow rate of 1.6 L/min. Results showed that there was no apparent matrix effect between the NIST SRM 610 and scheelite by this proposed method. With internal standardization against W, the obtained concentrations of CaO and WO₃ were found to yield an average matrix CaO/WO₃ mass fraction ratio of 0.245 (2σ = 0.003, n = 19), which agreed well with the value of 0.243 (2σ = 0.002, n = 15) from electron probe microanalysis (EPMA). Furthermore, the accuracy of trace element analyses with this proposed non-matrix-matched calibration in situ method was evaluated by comparing the concentration results with those from bulk analysis by solution nebulizer ICP-MS (SN-ICP-MS). It was found that the quantification results from LA-ICP-MS and SN-ICP-MS were comparable, in particular showing a relative concentration bias of the total ∑REE+Y contents of less than 2%. This confirmed that scheelites can be accurately analyzed in situ by LA-ICP-MS without matrix-matched calibration standards. By using this developed in situ method, the element compositions in a series of scheelite samples from different W-associated deposits in China were successfully quantified, promising further genetic process investigation and associated geologic activities of the polymetallic resources.

Keywords: major and trace element; nanosecond LA-ICP-MS; non-matrix-matched calibration; scheelite sample.

Grants and funding

This research was funded with financial support from the National Key Research and Development Project, China grant number 2021YFC2901902; the Natural Science Foundation, China, grant number 42103009; and the Natural Science Basic Research Program of Shaanxi Province, China, grant number 2020JQ-974.