X-ray fluorescence analysis of Cr, As, Se, Cd, Hg, and Pb in soil using pressed powder pellet and loose powder methods

Quantitative analyses of Cr, As, Se, Cd, Hg, and Pb in soil were performed using wavelength dispersive X-ray fluorescence (WDXRF) spectrometry with pressed powder pellet and loose powder methods. Standard soil samples containing hazardous metals were prepared by adding appropriate amounts of aqueous standards to base soils and then drying and homogenizing them. Base soil powders ground to less than 12.5 mu m of modal particle size were Tachikawa loam, brown forest soil, and weathered granite containing 17.9,9.43, and 3.49 mass% of Fe2O3, respectively. Analytical lines were CrK alpha, AsK alpha, SeK alpha, CdK alpha, HgL alpha, and PbL beta, with accompanying corrections for overlapping of SeK beta to PbL beta and PbL alpha to AsK alpha. Specimens for XRF analysis were prepared using powder pellets pressed to 23 mm internal diameter of an Al ring with 300 kgf cm(-2), and loose powder in a 31 mm internal diameter polyethylene cup covered with 6-mu m thickness of polypropylene film. Calibration curves drawn using the proposed standards showed good linearity under 3000 mg kg(-1) for the five metals, and 300 mg kg(-1) for Hg. Corrections with Compton scattering for AsK alpha, SeK alpha, CdK alpha, HgL alpha, and PbL beta, and with background scattering for CrK alpha were effective and produced identical inclinations of calibration curves. CdK alpha having larger critical depth in the loose powder specimen showed merely smaller inclination of calibration curve than that of the pressed powder specimen because of optical shading. The spike test for five analytes showed good recovery for gravel soil and pumice soil. Copyright (C) 2009 John Wiley & Sons, Ltd.