Determination of fluorine and chlorine in iron ore using combustion ion chromatography

Importance of the Topic

Iron ore is the primary raw material for steel manufacturing, and its quality directly affects industrial processes and environmental safety. Fluorine and chlorine impurities can generate toxic combustion by-products, pose health hazards, and accelerate corrosion in iron-based materials, making their accurate determination essential for mining quality control and regulatory compliance.

Objectives and Study Overview

This work presents the development and validation of an automated combustion ion chromatography (CIC) method for simultaneous quantification of fluorine and chlorine in iron ore. Performance metrics such as chromatographic separation, calibration linearity, detection limits, and method precision were evaluated using six representative ore samples.

Methodology

Samples (10–15 mg) were mixed with tungsten oxide as a combustion aid and subjected to pyrolysis at 1000–1100 °C in a quartz tube with a ceramic insert. Resulting halogen gases were absorbed into deionized water and directly injected (100 µL) into an ion chromatograph equipped with a 30 mM KOH eluent and suppressed conductivity detection. A 15-minute run time provided baseline separation of fluoride, chloride, and common anions.

Instrumentation

• Dionex Integrion HPIC system with eluent generation, conductivity detector, suppressor, and column oven
• Mitsubishi AQF-2100H automatic combustion unit (HF-210 furnace, GA-211 absorption unit, ABC-210 boat controller)
• Dionex IonPac AS18-Fast-4 µm guard and analytical columns
• EGC 500 KOH cartridge, CR-ATC 600 trap column, ADRS 600 suppressor

Results and Discussion

The Dionex IonPac AS18-Fast-4 µm column achieved complete resolution of fluoride and chloride within 15 minutes. Calibration curves exhibited excellent linearity (r²>0.999). Limits of detection were 0.762 µg/g for fluorine and 0.738 µg/g for chlorine. Triplicate analyses of six ore samples yielded relative standard deviations below 3% for both analytes, demonstrating high reproducibility.

Benefits and Practical Applications

• Fully automated CIC workflow minimizes manual handling and potential contamination
• Reagent-free eluent generation enhances reproducibility and reduces maintenance
• Applicable to quality assurance in mining, steel production, and environmental monitoring

Future Trends and Applications

Emerging developments may include coupling CIC with mass spectrometry for detailed halogen speciation, miniaturized combustion modules for on-site testing, and method extension to additional solid matrices and halogen species.

Conclusion

The automated CIC method described offers a robust, sensitive, and precise solution for measuring fluorine and chlorine in iron ore, supporting industrial quality control and environmental safety standards.

References

• Ando M, Tadano M, Yamamoto S. Health effects of fluoride pollution caused by coal burning. Sci Total Environ. 2001;271(1–3):107–116.
• Liu G-r, Zheng M-h, Cai Z-w. Dioxin analysis in China. TrAC Trends Anal Chem. 2013;46(6):178.
• Thermo Scientific Technical Note 72211. Combustion ion chromatography with a Dionex Integrion HPIC System. 2017.
• Mitsubishi Chemical Analytech. Operation Manual for AQF-2100H Combustion Unit; Instruction Manual of Absorption Unit GA-210.
• Thermo Fisher Scientific. IonPac AS18-Fast-4 µm column manual.
• ICH Q2B Validation of Analytical Procedures: Methodology. 1996.