This non-destructive method is for determining sulfur in liquid distillate and residual oils, using non-dispersive x-ray fluorescence. The range of detection is 100 ppm up to 5 mass-%. The method has two interferences, molybdenum and lead that, when either is present at levels above 100 ppm, cause sulfur peak overlap and will negate use of this method. Higher levels of other metals can also cause interferences. The interference is not obvious and, therefore, questionable samples must be analyzed for these compounds before the determination of sulfur can be made. Suitable screening techniques include energy dispersive x-ray or atomic absorption spectroscopy.

The method is written for use with a Horiba Model SLFA-800 instrument, however, other equivalent equipment is satisfactory.