Determination of phthalates in PVC by thermal desorption-GC/MS Part 1: Determination of the thermal desorption temperature zone by EGA

Importance of the Topic

Phthalates are commonly used plasticizers in polyvinyl chloride (PVC) products, including toys and childcare articles. Because of health concerns and legal restrictions in regions such as the EU, US, and Japan, accurate and efficient analysis of restricted phthalates in PVC has become critical for quality control and regulatory compliance.

Objectives and Study Overview

This technical note explores the optimization of thermal desorption‐GC/MS for the determination of six regulated phthalates in PVC. The primary goal is to identify the optimal temperature range for thermal desorption using evolved gas analysis (EGA) to minimize matrix interference from high‐level plasticizers and PVC decomposition products.

Methodology and Instrumentation

Small PVC samples (≈20 mg) containing 40 % DINCH (non‐regulated plasticizer) and 0.1 % each of the six restricted phthalates were dissolved in THF. A 10 µL aliquot was deposited in a sample cup and the solvent evaporated to form a thin film. EGA‐MS analysis was performed to monitor characteristic ions and thermogravimetric events.

• Pyrolyzer: Multi‐shot EGA/PY‐3030D
• Temperature program: 100 – 600 °C at 20 °C/min
• EGA tube: UADTM-2.5N (2.5 m × 0.15 mm i.d.)
• GC oven: 300 °C (isothermal)
• Carrier gas: He at 1 mL/min, split ratio 1/20
• MS detection: monitoring m/z 149 for phthalates, m/z 155 for DINCH, and m/z 36 for HCl

Key Results and Discussion

EGA thermograms revealed distinct release regions for DINCH, HCl (from PVC dehydrochlorination), and aromatic decomposition products. By tracking ion fragments, the optimal thermal desorption window for the target phthalates was determined to be 100 – 320 °C. This range captures the phthalates efficiently while avoiding excessive background from PVC breakdown and high‐level plasticizer co‐elution.

Benefits and Practical Applications

Thermal desorption‐GC/MS with a defined desorption window offers a rapid, one‐step sample preparation that reduces analyst variability and eliminates solvent extraction. The method provides accurate quantification of regulated phthalates in PVC matrices for routine compliance testing and industrial quality control.

Future Trends and Potential Applications

Further development may include coupling EGA guidance with automated TD‐GC/MS workflows for high‐throughput screening and expanding the approach to other regulated additives. Advances in column technology and mass spectrometer sensitivity could enhance detection limits and selectivity.

Conclusion

An EGA‐guided TD‐GC/MS method has been established for reliable phthalate analysis in PVC. The identified desorption temperature zone (100 – 320 °C) ensures effective release of target analytes while minimizing matrix effects, supporting robust compliance monitoring.

References

• Yuzawa, et al., Anal. Sci., 25 (2009) 1057