X-ray fluorescence determination of total sulfur in fly ash

Standard addition, double dilution and standard calibration were used for x-ray fluorescence (XRF) determinations of sulfur in fly ashes. Samples were analysed as pellets prepared by mixing with acrylate copolymer or with microcrystalline cellulose (in the case of the double dilution method). Lithium sulfate was used for the standard addition method and also as standard with known sulfur content for the double dilution method. Fly ashes analysed by optical emission spectrometry with an inductively coupled plasma (ICP-OES) were used as standards for the standard calibration XRF method. Sulfur was determined in the range of ca. 10–1–100 % S. For the fly ashes from the North-Bohemian brown coals, the differences between the XRF determinations and the ICP-OES determinations ranged from ca. 1.4 to 10% rel. and precision (repeatability) was better than 10% (RSD). The standard calibration method is suitable for routine analyses of real samples of similar nature. The methods of standard addition and double dilution are rather laborious in sample preparation compared with the standard calibration.