Natural chromite as a reference material for LA-ICP-MS analyses: development and calibration

Abstract

This study comprehensively characterizes the natural chromite reference material UG1-W and establishes a methodological framework for its quantitative LA-ICP-MS analysis. Integrated mineralogical and geochemical analysis confirms exceptional homogeneity and validates optimized calibration approaches for UG1-W. High-resolution BSE imaging combined with automated mineralogy (TIMA) reveals a chromite–plagioclase dominated microstructure (80.8% chromite and 17.3% plagioclase) with minor accessory phases. Multi-analytical methods (LA-ICP-MS, EPMA, ICP-OES, ICP-MS, and TXRF) are employed to verify the homogeneity of both major and trace elements. Systematic calibration assessments yield three key findings: (1) persistent matrix-induced analytical biases occur when using synthetic glass standards; (2) calibration strategies yield divergent results despite employing internal standards; (3) matrix-matched calibration achieves superior accuracy for chromite analysis, exhibiting relative deviations below 5% against certified values. Collectively, this work establishes UG1-W as a homogeneous chromite reference material and unequivocally demonstrates the necessity of matrix-matched standardization for accurate LA-ICP-MS analysis of chromite. These findings significantly improve the measurement accuracy for refractory mineral systems and provide a robust analytical framework for geochemical studies of chromite-bearing lithologies.