Determination of sulphur in trace levels in petroleum products by wavelength-dispersive X-ray fluorescence spectroscopy

Determination of sulphur in trace levels in various petroleum products is important due to the deleterious effect of sulphur during the usage and further processing of these products. The environmental regulations of state and local agencies also restrict the sulphur content in distillate fuels to minimum acceptable levels. Sulphur content in low ppm levels in petroleum products can be determined by various standard methods, which are based on wet chemical and spectroscopic methods, proposed by agencies like ASTM, IP and UOP. The wet chemical methods are time consuming, tedious and require fine chemicals while the spectroscopic methods are applicable for relatively higher levels of sulphur. In the present work, a method has been developed for the determination of sulphur content in petroleum products up to 1 ppm level using wavelength-dispersive X-ray fluorescence (WDXRF) spectroscopy. The effect of various experimental parameters, viz. sample holder, sample mask, mylar film and sample matrix, which considerably influence the analysis, has been discussed. The developed method has been validated against the standard Raney nickel reduction method (UOP-375-80).