ISO 20884 Petroleum products - Determination of sulfur content of automotive fuels - Wavelength-dispersive X-ray fluorescence spectrometry
WARNING - The use of this International Standard may involve hazardous materials, operations and equipment. This International Standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this International Standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1 Scope
This International Standard 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 10 % (V/V) fatty acid methyl esters (FAME) and motor gasolines containing up to about 10 % (V/V) ethanol.

NOTE 1 Sulfur contents higher than 500 mg/kg can be determined after sample dilution. However, the precision was not established for diluted samples.

Products with higher oxygen content show significant matrix effects, e.g. FAME used as biodiesel. Nevertheless, FAME may be analysed when the corresponding procedures are followed (see 4.3 and 7.1).

Other products may be analysed with this test method. However, precision data for products other than those mentioned have not been established for this International Standard.

NOTE 2 For the purposes of this International Standard, the terms "% (m/m)" and "% (V/V)" are used to represent the mass fraction and the volume fraction of a material respectively.

2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3170, Petroleum liquids - Manual sampling
ISO 3171, Petroleum liquids - Automatic pipeline sampling

3 Principle
The sample under analysis is exposed in a sample cell to the primary radiation of an X-ray tube. The count rates of the SK-L2,3 X-ray fluorescence and, where required, the count rate of the background radiation are measured. The sulfur content of the sample is determined from a calibration curve defined for the relevant measuring range.

NOTE The IUPAC X-ray line notation (SK-L2,3) is used in this International Standard; the corresponding Siegbahn X-ray line notation (S-Kα) is being phased out.