Determination of chlorine and bromine in rubber products using hydropyrolytic combustion ion chromatography

Significance of the topic

Accurate quantification of halogen elements such as chlorine and bromine in rubber materials is essential for product quality, regulatory compliance and environmental safety. These halogens influence rubber performance, can generate toxic by-products during processing or disposal, and must be controlled according to international standards.

Objectives and study overview

The study demonstrates the application of ISO 7725:2020(E) Method A—a tubular furnace combustion approach coupled with ion chromatography—for the determination of total chlorine and bromine in laboratory rubber items. Four types of rubber products were analyzed to validate precision, sensitivity and recovery.

Methodology

Combustion ion chromatography (CIC) was employed. Key steps included:

• Pyrolysis of solid rubber samples (70–100 mg) in an oxygen/argon stream at 900 °C–1 000 °C to convert halogens into HCl and HBr.
• Sparging of combustion gases into an aqueous hydrogen peroxide absorbing solution to form chloride and bromide anions.
• Separation and detection of anions on a Dionex IonPac AS18-Fast column with suppressed conductivity.
• Calculation of halogen content using a constant volume factor determined via a phosphate standard.

Used instrumentation

• Nittoseiko AQF-2100H automated combustion furnace with horizontal electric furnace, gas absorption unit and sample changer modules.
• Thermo Scientific Dionex ICS-6000 HPIC system including dual‐pump module, eluent generator, conductivity detector and Chromeleon CDS software.

Results and discussion

Calibration exhibited excellent linearity (r2 ≥ 0.998) over 0.24–78 mg/L chloride and 0.01–1.02 mg/L bromide, with limits of detection around 0.3 mg/L. Four rubber items showed chlorine contents from 0.011 % to 0.79 % (w/w) and trace levels of bromine (< 0.01 % w/w). Repeatability was maintained with RSDs below 10 % over five replicates and after 10 days. Spiked recovery tests yielded 80 %–99 % accuracy for chloride and bromide.

Practical benefits and applications

• Fully automated sample combustion and IC analysis reduces manual handling and potential contamination.
• Sensitive and precise detection meets regulatory requirements for rubber product testing.
• Method adaptability allows simultaneous analysis of other anions (e.g., sulfate) with minor adjustments.

Future trends and applications

Advances may include integration with mass spectrometric detectors for enhanced selectivity, miniaturized combustion cells for high‐throughput screening, and expanded use in environmental matrices and polymer quality control across industries.

Conclusion

The combination of an AQF-2100H combustion furnace with a Dionex ICS-6000 HPIC system provides a robust, automated and compliant approach for the determination of total chlorine and bromine in rubber materials according to ISO 7725:2020(E), delivering high precision, sensitivity and ease of operation.

References

• ISO 7725:2020(E) Rubber and rubber products – Determination of chlorine and bromine content.
• Thermo Fisher Scientific Application Note 73865: Pyrohydrolytic combustion ion chromatography: Determination of total chlorine and sulfur in cleanroom gloves, 2020.
• Thermo Fisher Scientific Application Note 73280: Determination of fluorine and chlorine in iron ore using combustion ion chromatography, 2019.
• Thermo Fisher Scientific Technical Note 000767: Combustion ion chromatography with a Dionex Integrion HPIC system using Chromeleon 7 CDS software, 2022.