Validation of portable monochromatic X-ray fluorescence for plant elemental analysis using standard reference...

Monitoring metal(loid) contamination in plants across polluted landscapes requires analytical methods that are fast, quantitative, and cost-effective. Portable X-ray fluorescence offers these advantages, but its performance in plant matrices remains poorly validated. Here, we evaluate a first-generation portable monochromatic X-ray fluorescence analyzer (MXRF) using plant-based standard reference materials and field-collected plant samples from a reclaimed tailings pond. We assessed analytical performance and measurement-related factors and compared MXRF measurements with inductively coupled plasma mass spectrometry to identify matrix effects influencing inter-method agreement. Under optimized conditions, MXRF provided robust quantification of Cu, Mn, and Fe; acceptable performance for Zn, K, Ca, Se, and Re; and limited reliability for P, S, and Ti. Inter-method agreement was associated with controllable matrix effects, including sample mass-, homogeneity-, and concentration-dependent constraints. These findings identify analytical constraints and comprehensive quality-control standards for handheld MXRF plant elemental analysis, support its use for environmental plant monitoring workflows, and provide a validation template for evaluating future handheld MXRF systems.