The use of a portable X-ray fluorescence spectrometer for measuring nickel in plants: sample preparation and validation

Abstract

Abstract X-ray fluorescence is a fast, costly, and eco-friendly method for elemental analyses. Portable X-ray fluorescence spectrometers (pXRF) have proven instrumental in detecting metals across diverse matrices, including plants. However, sample preparation and measurement procedures need to be standardized for each instrument. This study examined sample preparation methods and predictive capabilities for nickel (Ni) concentrations in various plants using pXRF, employing empirical calibration based on ICP-OES Ni data. The evaluation involved 300 plant samples of 14 species with varying patterns of Ni accumulation. Various dwell times (30, 60, 90, 120, 300 s) and sample masses (0.5, 1.0, 1.5, 2.0 g) were tested. Calibration models were developed through empirical and correction factor approaches. Results showed that using less than 1.0 g of sample and dwell time below 60 seconds for the study conditions led to decreased Ni detection by pXRF. Ni concentrations determined by ICP-OES were highly correlated (R² = 0.94) with those measured by the pXRF instrument. Therefore, pXRF can provide reliable detection of Ni in plant samples, avoiding the digestion of samples and reducing the decision-making time in environmental management.