Preparative HPLC followed by GPC-MS to investigate the potential leachable compounds produced by the degradation of pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate)

Significance of the Topic

Investigating degradation products of high-performance polymer additives is critical for ensuring material stability and safety. Sterically hindered phenolic antioxidants such as pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) (additive 1010) protect plastics against thermo-oxidative degradation but may generate lower-molecular-weight fragments that migrate into contacting media. Characterizing these non-intentionally added substances supports regulatory compliance and risk assessment of polymer materials.

Study Objectives and Overview

This study demonstrates a combined preparative HPLC and gel permeation chromatography–mass spectrometry (GPC-MS) workflow to isolate and identify high-molecular-weight fragments resulting from additive 1010 degradation. Seven fractions were collected by preparative HPLC, concentrated, and analyzed by GPC-MS to elucidate potential leachable compounds.

Methodology

• Preparative HPLC fractionation using a C18 reversed-phase column with water/methanol gradient and UV detection at 270 nm to separate additive 1010 and its degradation products into seven discrete fractions.
• Concentration of collected fractions under vacuum and redissolution in chloroform prior to GPC-MS analysis.
• GPC separation by molecular size on Resipore columns with chloroform mobile phase, coupled to a single quadrupole mass detector operating in SCAN and SIM modes for fragment identification.

Instrumentation

• Agilent Infinity II preparative system: 1290 Infinity Binary pump, 1260 Infinity DAD, 1260 Infinity Fraction Collector.
• Agilent Infinity 1260 system with single quadrupole MS detector.
• Zorbax SB C18 preparative column, 21.5 × 50 mm, 5 µm.
• Agilent Resipore GPC columns, 4.6 × 250 mm.

Key Results and Discussion

• High reproducibility of preparative HPLC confirmed by overlay of repeated injections.
• Seven fractions obtained and successfully concentrated for downstream GPC-MS.
• GPC-MS analysis of PS580 standard validated separation of oligomers with degrees of polymerization from 4 to 18, eluting between 16 and 19 min.
• Analysis of HPLC fractions revealed multiple degradation fragments of additive 1010, including:
  • 1010-I (C56H84O10): loss of one propionate arm;
  • 1010-II (C39H60O8): loss of two arms;
  • 1010-III (C69H100O12): absence of two tert-butyl groups;
  • 1010-IV (C65H92O12): missing two tertiary groups;
  • 1010-V (C52H76O10): loss of one arm and one butyl group.
• Isotope distribution patterns and SIM extraction facilitated confident structural proposals for each fragment.

Benefits and Practical Applications

• Efficient isolation and structural characterization of high-molecular-weight, nonvolatile additive degradation products.
• Supports safety evaluation of migrating compounds in plastic materials, including food-contact applications.
• Enhances analytical capabilities in polymer formulation, quality control, and regulatory compliance.

Future Trends and Opportunities

• Extension of the workflow to diverse polymer additives and more complex matrices.
• Integration with high-resolution mass spectrometry and non-targeted screening strategies for comprehensive profiling of NIAS.
• Automation and miniaturization of preparative and GPC separation steps to increase throughput.
• Development of environmentally friendly solvents and sustainable chromatography practices.

Conclusion

The combined preparative HPLC and GPC-MS approach provides a robust, reproducible strategy to isolate and identify high-molecular-weight degradation fragments of sterically hindered phenolic antioxidants. This method addresses challenges in characterizing non-intentionally added substances, thereby facilitating safety assessments and regulatory compliance in polymer applications.

References

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