ISO 20884:2019 specifies a wavelength-dispersive X-ray fluorescence (WDXRF) test method for the determination of the sulfur content of liquid, homogeneous automotive fuels from 5 mg/kg to 500 mg/kg, which have a maximum oxygen content of 3,7 % (m/m). This product range covers:— diesel fuels containing up to about 30 % (V/V) fatty acid methyl esters (FAME),— motor gasolines containing up to about 10 % (V/V) ethanol,— synthetic fuels such as hydrotreated vegetable oil (HVO) and gas to liquid (GTL) having sulfur contents in the range of 5 mg/kg to 45 mg/kg.Products with higher oxygen content show significant matrix effects, e.g. pure FAME used as biodiesel, nevertheless, pure FAME can be analysed when the corresponding procedures are followed (see 5.3 and 8.1).Other products can be analysed with this test method, though precision data for products other than those mentioned have not been established for this document.NOTE 1 Sulfur contents higher than 500 mg/kg can be determined after sample dilution, however, the precision was not established for diluted samples.NOTE 2 For the purposes of this document, "% (m/m)" and "% (V/V)" are used to represent the mass fraction, w, and the volume fraction, φ, of a material respectively.