Uncertainty evaluation of Cd concentration in sphalerite by ICP-OES: a comparative study between GUM and Monte Carlo methods

Abstract

Accurate determination of cadmium (Cd) in sphalerite using ICP-OES is challenged by the absence of robust calibration models and standardized quality assessment methodologies. This study employs weighted least squares (WLS) linear regression to optimize the calibration of instrumental responses and carries out a systematic comparison between the Guide to the Expression of Uncertainty in Measurement (GUM) and the Monte Carlo method (MCM). An original method for evaluating the uncertainty of Cd concentration in sphalerite is established by integrating MCM-based uncertainty evaluation with WLS. The results indicate that the expanded uncertainty from the GUM deviates by up to 57.43% compared to the MCM, based on the WLS calibration. The MCM offers a more realistic approximation of the measurement distribution by incorporating large-scale random sampling and nonlinear coupling effects. In addition, WLS is recommended for signal calibration during the measurement, resulting in a standard deviation 62.84% lower than that of the ordinary least squares (OLS). Overall, integration of WLS calibration and MCM uncertainty evaluation is beneficial for improving the accuracy and reliability of Cd quantification in sphalerite by ICP-OES.