Fully automated sample preparation for the determination of plasticizers in PVC from food contact materials and toys

Importance of the topic

PVC-based food contact materials and toys can release plasticizers such as phthalates into consumables, often exceeding regulatory limits.
Strict European regulations cap phthalate content in toys below 0.1% and restrict hazardous substances in electronic equipment.

Objectives and Overview of the Study

This work presents a fully automated sample preparation workflow for quantifying a broad range of plasticizers in PVC samples via GC-FID and GC-MS.
The method combines direct analysis with a transesterification step to detect phthalates, epoxidized oils, and polyadipates as sum parameters and individual analytes.

Methodology and Instrumentation

• Sample Preparation: 50 mg PVC dissolved in tetrahydrofuran, precipitated with ethanol.
• Direct Analysis: Supernatant injected without derivatization to identify native plasticizers.
• Transesterification: Reaction with sodium ethoxide in ethanol (approx. 2 min), quenched by citrate buffer to form ethyl esters.
• Verification: Internal standard (1-ethyl naphthalene) monitors transesterification yield via DMPi/DEPi ratio.
• Analyte Coverage: Phthalates quantified as sum parameters, epoxidized oils via fatty acid ethyl esters, polyadipates via diethyl adipate calibration.

Použitá instrumentace

• PAL RTC autosampler with dilutor, injector tools, vortex mixer, and wash modules.
• GC Trace 1310 with split injection (0.5–2 μL, split flow 20 mL/min, 250 °C injector).
• Column: 20 m × 0.25 mm ID, 0.15 μm 100% dimethylpolysiloxane.
• Carrier Gas: Hydrogen for FID, Helium for MS at 60–80 kPa constant pressure.
• Oven Program: 60 °C (0.5 min), 30 °C/min to 110 °C, then 50 °C/min to 300 °C.
• Detector: FID or DSQ II mass spectrometer (Thermo Scientific).

Main Results and Discussion

The automated procedure achieved complete transesterification of DEHP to DEP via EHEP within 45 seconds, with no significant saponification up to 240 seconds.
The verification ratio (DEPi/EN) reliably flagged incomplete derivatization or blocked reagent addition.
GC cycle times of 10 minutes enabled high-throughput analysis of up to 40 different plasticizers across direct and derivatized samples.

Benefits and Practical Applications

• Fully automated protocol reduces manual labor, standardizes derivatization conditions, and minimizes variability.
• Simultaneous direct and transesterified analysis extends analyte coverage to phthalates, epoxidized oils, and polyadipates.
• Verification scheme ensures method robustness and compliance with regulatory thresholds.

Future Trends and Applications

Integration of this workflow into regulated laboratories can support routine screening of food contact materials and toys.
Adapting the automated platform for other polymers and matrices, and coupling with high-resolution MS, may further expand analytical reach and sensitivity.

Conclusion

The presented fully automated sample preparation and GC analysis provide a reliable, high-throughput solution for plasticizer determination in PVC-based products, ensuring compliance with stringent regulatory standards.

References

1. McCombie G, Harling-Vollmer A, Morandini M, et al. Eur Food Res Technol. 2012;235:129–137.
2. Directive 2005/84/EC of the European Parliament and of the Council. 14 Dec 2005.
3. Directive 2011/65/EU of the European Parliament and of the Council. 8 Jun 2011.
4. Biedermann-Brem S, Biedermann M, Fiselier K, Grob K. Food Addit Contam. 2005;22(10):1274–1284.