Determination of volatile phthalate esters using polymer coated sample cups - Part 2 Effect of other polymer coatings

Importance of the topic

Volatile phthalate esters such as dimethyl phthalate (DMP) and diethyl phthalate (DEP) are common plasticizers that present analytical challenges due to sample loss through evaporation. Ensuring accurate, precise quantification of these compounds is crucial in fields ranging from environmental monitoring to quality control of consumer products.

Objectives and study overview

This study extends previous work on polyvinyl chloride (PVC) coated sample cups to evaluate two additional polymer coatings—polystyrene (PS) and polymethyl methacrylate (PMMA)—for their ability to retain phthalate esters during thermal desorption–gas chromatography/mass spectrometry (TD-GC/MS) analysis.

Methodology and instrumentation

Glass sample cups (outer diameter 4 mm, inner diameter 3 mm, height 8 mm) were coated with a 2.4 µm film of PVC, PS, or PMMA and conditioned at 200 °C for 60 min in air. Each cup was spiked with 10 µL of a dichloromethane solution containing 15 phthalate esters (10 ppm each). After a 200 min standing time, samples were analyzed using the ASTM D7823 method. A Multi-Shot Pyrolyzer (EGA/PY-3030D, Frontier Laboratories) interfaced directly to the split injector of a GC/MS system performed thermal desorption and separation.

Main results and discussion

Polymer-coated cups provided quantitative retention of all targeted phthalate esters after 200 min, compared to significant losses in uncoated cups. Reproducibility of peak areas was within 2 % relative standard deviation (n=5), in line with ASTM requirements. No interfering signals from polymer pyrolyzates, oligomers or additives were detected for PVC, PS or PMMA coatings.

Benefits and practical applications of the method

• Enhanced accuracy and precision in phthalate ester analysis by minimizing evaporation losses.
• Compatibility with standard TD-GC/MS protocols (ASTM D7823).
• Absence of polymer-derived interferences simplifies data interpretation.
• Applicable to QA/QC workflows in environmental labs, polymer additive testing, and safety screening of consumer goods (e.g., toys).

Future trends and possibilities

Further developments may explore alternative polymer coatings with tailored selectivity, integration with automated sampling systems, miniaturized cup designs for microscale analysis, and coupling with high-resolution mass spectrometry to expand the range of detectable additives.

Conclusion

Polymer-coated sample cups (PVC, PS, PMMA) effectively prevent volatile phthalate ester losses during sample preparation and thermal desorption. This approach yields reproducible, interference-free data in compliance with ASTM D7823, offering a robust solution for accurate phthalate analysis.

References

• Frontier Laboratories Ltd. Technical Note PYA1-076E, Multi-functional Pyrolyzer®: Determination of Volatile Phthalate Esters Using Polymer-Coated Sample Cups—Part 2.
• ASTM International. ASTM D7823: Standard Test Method for Phthalate Esters in Polymer Products by Thermal Desorption–Gas Chromatography Mass Spectrometry.
• Related Technical Notes: PYA1-063E, PYA1-064E, PYA1-068E, PYA1-069E, PYA1-074E, PYA1-075E.