Determination of Multi-Element in Geochemical Samples by Ultra-High Pressure Sample Preparation

Reducing the diameter of pressed pellets for X-ray fluorescence （XRF） spectrometry enables high-pressure and ultra-high-pressure sample preparation at lower applied pressures. Based on saturated sample weight calculations， reducing the pellet diameter from 32 to 24 mm allows the sample mass to be decreased by approximately 50% while still achieving the saturated weight. Scanning electron microscopy （SEM） analysis of pellet surface morphology revealed that ultra-high-pressure preparation produces denser， smoother， and flatter pellets. This reduces measurement errors caused by surface irregularities and enables the pressing of poorly cohesive high-silica samples. For a 24 mm diameter pellet， a collimator mask diameter of 20 mm is used during measurement. For a 32 mm diameter pellet， a 30 mm collimator mask is used. Reducing the fluorescence irradiation area from a 30 mm diameter to a 20 mm diameter theoretically reduces sensitivity to 0.44 times the original value. However， the root mean square deviation （RMS） of the calibration curve， method accuracy， and detection limits remained essentially consistent. This study employed ultra-high-pressure preparation （2264 MPa） to produce 24 mm diameter pellets and established an analytical method using a 20 mm collimator mask. Thirty-four elements in geochemical exploration samples were determined. The accuracy and detection limits of the method meet the requirements for geochemical sample analysis. This approach achieves high-pressure sample preparation without requiring a higher-tonnage press and offers the advantage of reduced sample consumption.