Analysis of Low-Level Sulfur in Petroleum Products in Accordance with ISO 20884:04 and ASTM D2622-10

Sulfur occurs naturally in crude oil, in concentrations typically ranging from 0.5 – 5.0 wt%. However, research has shown that the presence of sulfur in road fuels, at just a few hundred mg/kg, makes automobile pollution a major contributor to greenhouse gas emission and smog formation. Exhaust emissions of sulfur as sulfur dioxide and sulfate particulates directly contribute to the pollution load. However, the main drive for reducing the sulfur level of fuel is to maximize the CO2 reduction potential of new fuel-efficient engine technology and to improve the efficiency of emission control devices, such as catalytic converters, reducing emissions of NOx and particulates.

In the United States the EPA Tier 2 regulations (2002) set an upper limit of 150 mg/kg for the sulfur content of road fuels. However, in the European Union even more stringent regulations are being set. The EU Directive
98/70/EC requires that, from 2005 onwards, the sulfur level in road fuels does not exceed 50 mg/kg (Emission Standard Euro IV). This is to be followed by Euro V, which requires a reduction of sulfur in fuel to a maximum of 10mg/kg in 2009. X-ray fluorescence spectrometry is used extensively for the analysis of sulfur in petroleum products. Simple sample preparation, high accuracy and precision, and good to excellent detection limits (0.2 – 1 mg/kg) are the principal reasons for this choice, and make it an excellent technique for production control.

International Standard Test Methods
Both ASTM 2622 and ISO 20884 methods are broadly analogous, employing mathematical matrix corrections, and are distinct from ISO 14596, which employs a Zrinternal ratio correction method.

The latest 2010 version of ASTM D2622 is the most stringent test method in terms of repeatability and reproducibility.

In this study we have set up and made separate calibrations in accordance with the methods stipulated in both ASTM D2622-10 and ISO 20884:04 norms.

Preparation of Standards and Samples
Commercially available synthetic standards, prepared according to the test methods, were used for this study NIST Diesel SRM 2723a was used as purchased. Fifteen milliliters (15 ml) of sample material (standard or routine) were poured into 38 mm diameter disposable liquid cells, constructed using Mylar X-ray film.