ISO 14596 Petroleum products - Determination of sulfur content - Wavelength-dispersive X-ray fluorescence spectrometry
4 Reagents and materials
4.1 White oil (light paraffin oil, paraffinum perliquidum), high-purity grade, sulfur content 1 mg/kg maximum.
4.2 Sulfur compounds, of sulfur content accurately known to the nearest 0.01 % (m/m), used for the preparation of the primary standards.
The compounds given in 4.2.1 to 4.2.3 are suitable, and their nominal sulfur contents are given. Where the purity of these compounds is less than 99 %, certified materials are required, or the nature of all impurities and their contents should be accurately known to the nearest 0.01 % (m/m).
4.2.1 Dibenzothiophene (DBT), with a nominal sulfur content of 17.399 % (m/m).
4.2.2 Dibutyl sulfide (DBS), with a nominal sulfur content of 21.915 % (m/m).
4.2.3 Thionaphthene (benzothiophene) (TNA), with a nominal sulfur content of 23.890 % (m/m).
4.3 Certified sulfur reference materials.
Use materials from a national standards body or accredited suppliers, if available.
4.4 Zirconium solution A.
Zirconium octoate solution with a zirconium content in the range of 12 % (m/m) to 18 % (m/m) or another oil-soluble, sulfur-free zirconium compound dissolved in white oil (4.1) to provide a zirconium mass fraction in the range of 12 % (m/m) to 18 % (m/m).
4.5 Zirconium solution B.
Dissolve the zirconium solution A (4.4) with white oil (4.1) to provide a zirconium mass fraction of approximately 1 % (m/m).
5 Apparatus
5.1 Wavelength-dispersive X-ray fluorescence (WDXRF) spectrometer, consisting of any suitable spectrometer that incorporates the design features listed in Table 1. It shall be set up according to the manufacturer's instructions.
5.2 Analytical balance, capable of weighing to the nearest 0.1 mg.
5.3 Homogenizer, non-aerating, high-speed shear type, or heatable magnetic stirrer or, for example, an ultrasonic stirrer.
5.4 Flasks, 50 ml capacity, narrow-necked, conical, made of borosilicate glass and fitted with a ground-glass stopper. Use flasks of higher capacity for stock solutions (7.2).
6 Samples and sampling
6.1 Unless otherwise specified, samples shall be taken in accordance with the procedure described in ISO 3170 or ISO 3171.
6.2 Test portions from the samples shall be drawn after thorough mixing and subdivision. Heat viscous samples to a temperature that renders the sample liquid and homogenize, using the homogenizer (5.3) as necessary.
NOTE For the purpose of this procedure, the term "sample" also includes solutions prepared from additives, semi-solid or solid petroleum products that have been appropriately pre-treated and/or diluted.
