CERTIFICATION OF SULFUR IN SRM-2724 DIESEL FUEL-OIL BY ISOTOPE-DILUTION THERMAL IONIZATION MASS-SPECTROMETRY AND X-RAY-FLUORESCENCE

SRM 2724 is a no. 2-D diesel fuel oil that has been certified for total sulfur concentration at 425 +/- 4 mug g-1 (95% confidence interval) by isotope dilution thermal ionization mass spectrometry, which is the most accurate and precise method for the determination of sulfur in many different matrices. The sulfur concentration in this standard has also been measured by X-ray fluorescence (XRF) using a procedure derived from ASTM method D 2622-87. The mean of the XRF measurements was 423 +/- 2 (1s), which demonstrates that XRF is capable of measuring sulfur accurately and precisely at the 500 mug g-1 level when it is properly calibrated using accurately certified standards of a similar matrix. SRM 2724 will be useful in validating the measurement process for the determination of sulfur by XRF in on-road diesel fuel at the 500 mug g-1 limit as mandated by EPA, effective from October 1993.