Determination of chlorine, bromine, and sulfur in polyethylene materials using combustion ion chromatography

Importance of the Topic

Polyethylene is one of the most widely used plastics in packaging, medical devices, and consumer goods. Halogen- and sulfur-based additives such as flame retardants and stabilizers improve material properties but pose environmental and health risks when discarded or recycled. Accurate quantification of chlorine, bromine, and sulfur in polyethylene supports regulatory compliance, quality control, and safe material management.

Objectives and Study Overview

This study aimed to develop and validate an automated combustion ion chromatography (CIC) method for simultaneous determination of chlorine, bromine, and sulfur in various polyethylene samples. Four polymer types—including low‐density, high‐density, ultrahigh‐molecular‐weight polyethylene, and PVC‐based wrap—were analyzed. Method accuracy was assessed using a certified reference material (ERM EC680k) and spike recovery experiments.

Methodology

Samples (20–35 mg) were thermally decomposed under an argon atmosphere and combusted in oxygen at high temperature. The resulting gases were absorbed into an aqueous hydrogen peroxide solution to convert halogens to halide ions and sulfur oxides to sulfate. A portion of the absorption solution was injected into a high‐pressure Dionex Integrion HPIC system equipped with a self‐regenerating KOH eluent generator and a 2 × 250 mm IonPac AS11-HC column. Separation was performed isocratically with 25 mM KOH at 0.38 mL/min and detection by suppressed conductivity.

Instrumentation Used

• Thermo Scientific Dionex Integrion HPIC system with eluent generation, column oven, and suppressed conductivity detector
• Mitsubishi Automatic Combustion Unit AQF-2100H with electric furnace, gas absorption unit, and automatic boat controller
• Thermo Scientific Dionex AS-AP autosampler with 10 mL vial trays

Main Results and Discussion

Calibration by both direct and combusted standards provided linear responses for Cl⁻, Br⁻, and SO₄²⁻. CRM analysis yielded recoveries of 95–105 % and RSDs below 2.4 %. Four polyethylene samples showed measurable chlorine and sulfur levels, while bromine was not detected, reflecting current additive usage. Spike recoveries ranged from 92 % to 115 %, confirming method accuracy. Chromatograms demonstrated clear resolution of halide and sulfate peaks within a 10 min runtime.

Benefits and Practical Applications

The CIC approach offers fully automated sample introduction, minimal sample preparation, and reduced chemical waste compared to acid digestions and solvent extractions. High sensitivity and precision make it ideal for polymer manufacturers, recyclers, and environmental laboratories monitoring halogen and sulfur content for product specifications and regulatory compliance.

Future Trends and Applications

• Integration of CIC with mass spectrometric detection for molecular speciation of sulfur and halogen-containing additives
• Miniaturized combustion modules for field and on‐site polymer screening
• Extension of the method to other plastics and composite materials
• Software-driven data analytics and AI for trend monitoring in material formulations

Conclusion

The presented CIC method demonstrates robust performance for simultaneous analysis of chlorine, bromine, and sulfur in polyethylene samples. Its high throughput, accuracy, and low environmental impact support its adoption in quality assurance and compliance testing workflows.

Reference

• Deanin RD. Additives in plastics. Environ Health Perspect. 1975;11:35–39.
• DIN EN 62321-3-2. Determination of halogens in polymers by combustion ion chromatography. 2016.
• Thermo Scientific Application Note 1145: Halogens in Coal Using CIC. 2016.
• Thermo Scientific Technical Note 72211: CIC with Integrion HPIC. 2017.
• Thermo Scientific Technical Note 175: Configuring Integrion HPIC. 2016.
• Mitsubishi Chemical Analytech. Operation Manual for AQF-2100H Combustion Unit.