Determination of sulfur in petroleum products according ASTM D4294

Importance of the topic

Accurate determination of sulfur in petroleum fuels is critical for ensuring product quality and complying with stringent environmental regulations that limit sulfur to prevent harmful emissions. Rapid screening methods enable refineries and distributors to monitor ultra-low-sulfur diesel production in real time and maintain compliance with international standards.

Objectives and Overview of the Study

This application note evaluates the performance of the Thermo Fisher ARL QUANT’X EDXRF spectrometer following ASTM D4294 for measuring sulfur concentrations in petroleum products. Focus is placed on the low-range calibration (0–1000 mg/kg), assessment of precision and accuracy, determination of the limit of detection, and demonstration of suitability for quality control.

Methodology and Instrumentation

The ARL QUANT’X uses a 50 kV, 50 W silver-target X-ray tube and a state-of-the-art silicon drift detector. Samples are measured in sealed 32 mm cups with a 4 μm polypropylene film, using helium atmosphere to minimize X-ray absorption by air. A thin graphite filter optimizes the signal-to-background ratio for the sulfur K-line at an excitation voltage of 9 kV. Live measurement time is 100 seconds, with tube current adjusted for a 50% dead time.

Main Results and Discussion

Calibration across ten standards (0–1000 mg/kg) achieved an R2 of 0.99999 and an RMSE of 1.45 ppm using a second-order fit. Repeatability tests at 10.4, 120, and 499.1 ppm sulfur yielded standard deviations of 0.44, 0.51, and 1.05 ppm, respectively, demonstrating high precision and accuracy. The 100-second limit of detection is 1.05 ppm, which can be improved to 0.6 ppm with a 300-second count.

Benefits and Practical Applications

The EDXRF method offers rapid, non-destructive analysis with minimal sample preparation, meeting the detection requirements for ultra-low-sulfur diesel in accordance with ASTM D4294. It streamlines quality control workflows in refining and distribution environments.

Future Trends and Potential Applications

Advances in detector technology, automated sample handling, and extended measurement times may further lower detection limits and expand applicability to other trace elements. Portable EDXRF instruments could enable in-field screening of petroleum products.

Conclusion

The ARL QUANT’X EDXRF spectrometer reliably quantifies sulfur at low ppm levels in petroleum, fulfilling ASTM D4294 requirements. Its accuracy, precision, and speed make it an effective tool for ultra-low-sulfur diesel quality control.

Instrumentation

• ARL QUANT’X EDXRF spectrometer
• 50 kV, 50 W silver-target X-ray tube
• Silicon drift detector (SDD)
• Helium flush option
• Thin graphite primary filter

Reference

• ASTM D4294: Standard Test Method for Sulfur in Petroleum Products by Energy Dispersive X-Ray Fluorescence Spectrometry