Determination of total fluorine, chlorine, and sulfur in aromatic hydrocarbons by oxidative pyrolytic combustion followed by ion chromatography

Importance of the Topic

Aromatic hydrocarbons containing fluorine, chlorine, and sulfur can lead to environmental pollution, catalyst deactivation, and corrosion in industrial processes. Accurate quantification of total halogens and sulfur is therefore essential for environmental monitoring, quality control, and regulatory compliance in petrochemical and related industries.

Study Objectives and Overview

This study presents a streamlined approach based on ASTM D7359-14a to measure total fluorine, chlorine, and sulfur in aromatic hydrocarbon matrices. Using a gasoline sample as a representative, the method couples oxidative pyrolytic combustion with ion chromatography to achieve efficient separation and quantitation of F−, Cl−, and SO42−.

Methodology and Instrumentation

The analytical workflow involves oxidative pyrolysis of liquid samples in a Mitsubishi AQF-2100H combustion unit at temperatures up to 1000°C under a controlled oxygen and argon atmosphere. Combustion gases are absorbed in a hydrogen peroxide solution and directly introduced into a Thermo Scientific Dionex Integrion HPIC system. Separation is achieved on an IonPac AS18-4 µm anion column with a potassium hydroxide gradient elution. Suppressed conductivity detection is performed using an AERS 500 suppressor in recycle mode. Calibration standards ranging from 0.2 to 10 mg/L are prepared via serial dilution from a 1000 mg/L stock solution. Key instrument settings include a flow rate of 1 mL/min, column temperature of 30°C, and an overall run time of 14.5 minutes.

Results and Discussion

The method provides baseline separation of fluoride, chloride, and sulfate within 14.5 minutes. Calibration curves exhibit linear responses over the 0.2–10 mg/L range with determination coefficients above 0.999. Precision studies at three concentration levels yielded retention time and peak area relative standard deviations below 4%. Spike recovery experiments in the gasoline matrix showed recoveries between 85% and 102%, confirming method accuracy and robustness.

Benefits and Practical Applications

• Matrix removal during combustion reduces interferences for complex hydrocarbon samples.
• Rapid analysis with high resolution and sensitivity supports routine QA/QC workflows.
• Applicability to diverse sample types such as fuels, polymers, and environmental specimens.

Future Trends and Opportunities

Advances may include coupling combustion ion chromatography with mass spectrometry for detailed speciation, development of miniaturized and field-deployable systems, and optimization of reagent consumption for greener workflows. Integration with automated data processing and remote monitoring will further enhance method utility.

Conclusion

The described combustion ion chromatography method demonstrates high linearity, precision, and accuracy for total fluorine, chlorine, and sulfur analysis in aromatic hydrocarbons. Its simplicity and robustness make it well suited for routine environmental and industrial applications.

Reference

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