Bromine content in polystyrene – optimization of the absorption solution for Combustion IC

Importance of the Topic

Brominated polystyrene is widely used as a flame retardant polymer and contains high levels of bromine typically between 25 and 35 percent by weight.
Reliable quantification of bromine is essential for material performance assessment compliance with regulatory requirements and quality control in industrial production.

Objectives and Study Overview

This study aimed to optimize the composition of the absorption solution used in combustion ion chromatography to achieve complete trapping of bromide released from high-bromine polystyrene samples.
Key goals included minimizing variability and maximizing recovery of bromide under varying reagent concentrations.

Methodology

Polystyrene samples containing bromine were combusted in a dedicated combustion module using argon and oxygen flows at 100 and 300 mL per minute respectively and an oven temperature of 1050 °C.
The post-combustion absorption solution was prepared with sodium hydroxide concentrations varying from 0 to 30 mmol per liter and hydrogen peroxide concentrations from 100 to 800 mg per liter.
Bromide recovery and relative standard deviation were assessed for each combination of reagent levels using partial loop injection and inline matrix elimination.
The ion chromatographic separation employed a Metrosep A Supp 16 analytical column with sequential suppression and conductivity detection after a 14-minute run at 45 °C.

Použitá instrumentace

• 930 Compact IC Flex with oven SeS PP and degasser
• IC Conductivity Detector
• MSM Rotor A and Adapter sleeve for Suppressor Vario
• 920 Absorber Module and Combustion Module with ABD
• Autosampler MMS 5000 and Kit for solid sampling
• Columns: Metrosep A Supp 16, A Supp 4/5 Guard, A PCC 1 HC, A Trap 1, I Trap 1

Results and Discussion

Optimal bromide recovery of approximately 281.5 grams per kilogram with an RSD of 1.8 percent was achieved using 20 mmol per liter NaOH and 400 mg per liter H2O2.
Lower NaOH concentrations led to incomplete trapping whereas higher levels showed no significant improvement.
Hydrogen peroxide concentration exhibited a minor influence on precision but a 400 mg per liter level provided the best compromise between oxidation capacity and baseline stability.

Benefits and Practical Applications

The optimized absorption solution enables robust analysis of high-bromine polymers with high precision and accuracy.
This method supports quality assurance in manufacturing flame retardant materials and ensures compliance with environmental regulations.
The streamlined workflow reduces reagent consumption and lowers the risk of incomplete bromide capture.

Future Trends and Potential Applications

Advances may include integration of mass spectrometric detection for enhanced selectivity miniaturization of combustion cells and use of alternative oxidizing agents to further improve recovery and safety.
Automation of sample preparation and data processing could increase throughput and reproducibility for routine industrial analysis.

Conclusion

By systematically varying sodium hydroxide and hydrogen peroxide levels the study established an absorption solution composition that ensures quantitative trapping of bromide from combusted polystyrene.
This optimized protocol delivers reliable results with low variability and is readily applicable to quality control laboratories.

References

1. Metrohm IC Application Note CIC–022 Version 1 September 2017