Extraction of Antioxidant from High Density Polyethylene

Significance of the Topic

Monitoring polymer additives is critical for quality control in plastics manufacturing and environmental compliance. Conventional solvent based methods for extracting antioxidants from polyolefin resins often require large volumes of toxic solvents and long processing times. Supercritical fluid extraction with CO2 offers an eco-friendly, efficient alternative that can reduce solvent use and shorten analysis times while maintaining analytical performance.

Objectives and Study Overview

This application note aims to demonstrate extraction of antioxidants from high density polyethylene using supercritical CO2. The goals include

• Reducing hazardous solvent consumption
• Shortening extraction time compared with traditional methods
• Maintaining accuracy and precision of additive quantitation

Methodology and Instrumentation

• Sample Preparation: Cryogenic grinding of 1.5 g polymer followed by mixing with 15 g Ottawa sand
• Instrument: Applied Separations Spe-ed SFE or Helix supercritical extraction system
• Extraction Vessel: 24 mL capacity loaded with glass wool plugs and sample
• Extraction Conditions: 7000 psi pressure, 140 C vessel and valve temperature, CO2 flow of 4 L/min for 30 min dynamic extraction
• Collection: C18 SPE cartridge (500 mg, 6 mL) to trap additives
• Elution: 5 mL methanol/methylene chloride (1:1) from SPE cartridge
• Analysis: HPLC determination of recovered antioxidant

Main Results and Discussion

Supercritical CO2 extraction achieved near quantitative recovery of antioxidant from HDPE in 30 min, matching performance of standard solvent methods. Precision and accuracy were comparable while extraction time and solvent waste were significantly reduced. The use of SPE cartridge allowed clean collection and straightforward elution prior to HPLC analysis.

Benefits and Practical Applications

• Reduced use of hazardous organic solvents
• Faster sample throughput for quality control
• Lower operational costs and improved safety
• Scalable technique for routine polymer additive analysis

Future Trends and Potential Applications

Integration of online SFE-SFC or SFE-HPLC workflows could further streamline analysis. Exploration of other polymer types and additives, use of green cosolvents and automated sample handling are promising directions. Scale up for high throughput industrial monitoring and coupling with mass spectrometry may extend applicability.

Conclusion

Supercritical CO2 extraction presents a viable, greener alternative to traditional solvent based extraction for polymer additives. It delivers comparable data quality in less time and with minimal solvent usage, meeting the needs of modern quality control laboratories.

References

• Ashraf-Khorassani M; Boyer D; Levy J Optimization of experimental parameters for the determination of polymer additives using online supercritical fluid extraction-supercritical fluid chromatography Journal of Chromatographic Science 29 1991 517-521