Total sulfur determination in petroleum fuels for routine quality control by sector field inductively coupled plasma mass spectrometry after dilution treatment

Abstract

Sulfur is found in petroleum fuels and is oxidized to create sulfur oxides during combustion, resulting in air pollution and acid rain. It is therefore important to monitor the trace sulfur content in petroleum fuels. An accurate, sensitive, and fast method is developed to determine the total sulfur content in petroleum fuels by means of sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). Gasoline- and diesel-type samples are directly introduced into the SF-ICP-MS system with a steady flow rate after 1000-fold dilution with isopropanol (IPA) and IPA containing 10% toluene, respectively. The concentration of sulfur in the petroleum fuels is quantified using a certified standard diluted in IPA or IPA–toluene solution as the external calibration system, without the need for any other pretreatments such as digestion or emulsion. The method detection limit values range from 0.12 to 0.17 ng g⁻¹ for different petroleum fuels. Fourteen petroleum fuels containing gasoline, ethanol-blended gasoline, diesel, and biodiesel obtained from the international proficiency testing program of the American Society for Testing and Materials and the Institute for Interlaboratory Studies are analyzed using the developed method. The Z-score values are in the range of −0.39 to 1.27 for all analytes, indicating good analytical accuracy for this method. Thirty petroleum fuels taken from refueling guns at petrol stations across Taiwan are analyzed directly using the developed method to demonstrate its practicality.