Analysis of total chlorine in oil by XRF at 1500W

Importance of the Topic

Chlorine content in oil can severely impact corrosion, refinery operations, and environmental compliance. Accurate low-level determination of chlorine is essential for ensuring product quality and safeguarding equipment longevity.

Objectives and Study Overview

This study aims to evaluate the performance of the ARL PERFORM’X sequential WD-XRF spectrometer, operating at 1500W with a rhodium anode tube, for quantifying total chlorine in oil samples. A calibration curve was developed following ASTM D4929 guidelines to assess accuracy and precision at low concentration levels.

Methodology

• Preparation of standards: A 1000 ppm chlorine concentrate was diluted with iso-octane to produce calibration standards ranging from 0 to 71.9 ppm.
• XRF measurement: Net peak intensities were recorded using identical counting times for the chlorine peak and background positions as recommended by ASTM D4929.
• Repeatability test: Six replicate measurements of an oil sample containing ~1.4 ppm Cl were performed under the same analytical conditions.

Instrumentation

• Instrument: Thermo Scientific ARL PERFORM’X WD-XRF Spectrometer
• Anode tube: Rhodium
• Crystal: Ge 111
• Detector: Flow proportional counter (FPC)
• Collimator: 0.40
• Operating parameters: 30 kV, 50 mA, 1500 W
• Counting times: 180 seconds per line, total 360 seconds
• Atmosphere: Vacuum to helium shutter for liquid analysis

Key Results and Discussion

• Calibration performance: Correlation coefficient R2 = 0.99975, Standard Error of Estimate = 0.51 ppm.
• Accuracy: Deviations between nominal and measured concentrations remained below 0.7 ppm across all standards.
• Repeatability: Six replicates of a 1.4 ppm sample yielded an average of 1.4 ppm with a standard deviation of 0.6 ppm, demonstrating robust reproducibility.

Benefits and Practical Applications

The ARL PERFORM’X WD-XRF offers rapid, non-destructive analysis with minimal sample preparation. High accuracy and precision at low chlorine levels make it suitable for quality control in petrochemical production and compliance testing.

Future Trends and Opportunities

• Integration of advanced detector technologies for lower detection limits.
• Automation and inline monitoring for real-time process control.
• Further method optimization to expand applicability to diverse matrix types.

Conclusion

The application of ASTM D4929 with a rhodium anode WD-XRF spectrometer yields reliable and precise chlorine measurements in oil, meeting the stringent demands of petrochemical quality assurance.

References

• Thermo Fisher Scientific. Application Note AN41675: Analysis of Total Chlorine in Oil by XRF at 1500W.