Analysis of ultra-low sulfur in diesel fuels according to ASTM2622-16 with Thermo Scientific ARL PERFORM'X 2500 XRF spectrometer

Importance of the topic

Reducing sulfur in diesel fuels is critical to meet tightening global regulations and to minimize emissions of sulfur oxides and fine particulate matter from combustion engines. Ultra-low sulfur diesel (ULSD) at 10 ppm or below protects catalytic converters, reduces environmental impact and aligns with current EPA and EU standards.

Study objectives and overview

This application note evaluates the performance of the Thermo Scientific ARL PERFORM’X 2500 WDXRF spectrometer for trace sulfur analysis in diesel, in accordance with ASTM D2622-16. Key goals include:

• Verifying detection limits and sensitivity for sulfur in the 0–20 ppm range
• Assessing precision and repeatability on real diesel samples
• Demonstrating ease of operation and compliance with ULSD quality control requirements

Methods and instrumentation

The analysis was performed on a Thermo Scientific ARL PERFORM’X 2500 WDXRF system configured with a 5 GN+ Rh X-ray tube, six primary beam filters, four collimators and up to nine analyzing crystals. A helium purge and medium collimator (0.4°) optimized background suppression for sulfur. Calibration standards from 0 to 20 ppm were prepared by diluting a 0.300 % reference material in blank oil. Measurement conditions:

• High voltage: 30 kV; tube current: 80 mA
• Analyzing crystal: PET
• Detector: flow proportional counter (FPC)
• Counting time: 100 s per measurement
• Background point included to improve accuracy at trace levels

Main results and discussion

The calibration curve exhibited excellent linearity from 0 to 20 ppm sulfur, with sensitivity of 351 kcps/% and a calculated detection limit of 0.1 ppm at 100 s. Repeatability tests on a 7.7 ppm diesel sample (15 replicate liquid cells) showed variations well within the ASTM D2622-16 maximum permissible difference of 0.75 ppm. This demonstrates both high stability and robustness of the ARL PERFORM’X over extended measurement sessions.

Benefits and practical applications

WDXRF analysis on the ARL PERFORM’X offers:

• Rapid, reproducible quantification of ultra-low sulfur without complex chemical pretreatment
• High sample throughput with safe automated loading and liquid cell handling
• Compliance with stringent regulatory requirements for routine quality control in refineries and fuel laboratories

Future trends and applications

Advances likely to enhance trace sulfur analysis include automated inline sampling, improved helium-free detection technologies, further miniaturization of XRF spectrometers and integration of advanced data analytics for real-time process monitoring and predictive maintenance in fuel production.

Conclusion

The Thermo Scientific ARL PERFORM’X 2500 WDXRF spectrometer meets and exceeds the requirements of ASTM D2622-16 for ultra-low sulfur analysis in diesel. It delivers sub-ppm detection limits, excellent precision and user-friendly operation, making it a reliable solution for both routine QC and research applications.