Development of soil reference materials containing hazardous metals for X-ray fluorescence analysis

Soil standards containing hazardous metals (Cr, As, Se, Cd, Hg, and Pb) were developed for X-ray fluorescence analysis (XRF). Standard soil was prepared by adding appropriate amount of aqueous standard solutions to the base soil (brown forest soil ; Fukuoka, Japan) and then drying and homogenizing. The analytical lines were CrK alpha, AsK alpha, SeK alpha, CdK alpha, HgL alpha and PbL beta accompanied by the corrections for the overlapping of SeK beta to PbL beta and PbL alpha to AsK alpha. Specimens for XRF analysis were prepared by a powder briquette molded in the 23 mm phi of an Al ring with 300 kgf cm(-2). The homogeneity and durability of the standards were checked by the fluorescent X-ray intensities and the statistical errors for briquette samples. Each of the intensities varied slightly, and the relative standard deviations of the XRF intensities of Cr, As, Se, Cd, and Pb in 10 briquettes were less than 0.3%. The X-ray resistant performance of the soil standards was checked by the repetitive irradiation of 4 kW X-ray. The fluorescence intensities of Cr, As, Se, Cd, and Pb showed constant values for 240 min of irradiation. The HgL alpha intensity was almost constant for 60 min of irradiation in air. The calibration curves constructed proposed standards showing good linearity under 3000 mg kg(-1) for Cr, As, Se, Cd, Pb, and 300 mg kg(-1) for Hg. The lower limits of detection were 0.84 similar to 2.7 mg kg(-1).