ISO 14596 Petroleum products - Determination of sulfur content - Wavelength-dispersive X-ray fluorescence spectrometry
1 Scope
This International Standard specifies a method for the determination of the sulfur content of liquid petroleum products, additives for petroleum products, and semi-solid and solid petroleum products that are either liquefied by moderate heating or soluble in organic solvents (see 4.1) of negligible or accurately known sulfur content. The method is applicable to products or additives having sulfur contents in the range 0.001 % (m/m) to 2.50 % (m/m); higher contents can be determined by appropriate dilution. Other elements do not interfere at concentrations anticipated in the materials subject to this analysis.
NOTE For the purposes of this International Standard, the term "% (m/m)" is used to represent the mass fraction of a material.
High concentrations of phosphorus or chlorine [typically above 3 % (m/m)] can cause bias in the sulfur result by absorbing Zr-Lα and S-Kα to different extents. It is necessary in these cases to carry out studies to determine whether this potential interference is significant.
When larger amounts of molybdenum are present (typically above 50 mg/kg to 100 mg/kg), increased background radiation and spectral overlap with the sulfur signal can occur. It is necessary in these cases to inspect the relevant spectral regions, for example, to investigate the significance of this potential source of bias.
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 3170:2004, Petroleum liquids - Manual sampling
ISO 3171:1988, Petroleum liquids - Automatic pipeline sampling
3 Principle
The test portion and a zirconium solution as internal standard are mixed in a given mass ratio and exposed, in a sample cell, to the primary radiation of an X-ray tube.
The count rates of the S-Kα at 0.537 3 nm and Zr-Lα1 at 0.607 0 nm fluorescence thus excited and the count rate of the background radiation at 0.545 nm are measured and the ratio of these net count rates calculated. The sulfur content of the sample is determined from a calibration curve prepared on the basis of sulfur calibration standards.
NOTE The Siegbahn X-ray line notation (S-Kα) is used in this International Standard; the corresponding IUPAC X-ray line notation is S K-L2,3.
