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

Importance of the Topic

Plasticizers in PVC-based food contact materials and toys can migrate into products, occasionally exceeding legal limits or involving banned compounds. Ensuring accurate, high-throughput monitoring supports consumer safety and regulatory compliance.

Objectives and Study Overview

This work aims to fully automate sample preparation and derivatization for the determination of up to 40 plasticizers—including phthalates, epoxidized oils, and polyadipates—in PVC matrices. The study evaluates direct analysis and transesterification to ethyl esters to enhance detection and confirmation of target analytes.

Methodology and Instrumentation

Sample pretreatment involves:

• Dissolution of ~50 mg PVC in tetrahydrofuran.
• Precipitation of PVC with ethanol and collection of supernatant.
• Parallel direct GC analysis or automated transesterification: addition of sodium ethylate, reaction for ~2 min, quenching with citrate buffer, extraction with MTBE/hexane.

Automation is performed on a PAL RTC autosampler with interchangeable tools (dilutor, wash, vortex, tray holder) to dispense up to five solvents and solutions. Verification of transesterification yield and saponification onset uses an inert internal standard (1-ethyl naphthalene) and DMPi-to-DEPi ratio monitoring.

Instrumentation details:

• Autosampler: PAL RTC (CTC Analytics).
• GC system: Trace 1310.
• Detector: FID or DSQ II MS (Thermo Scientific).
• Column: 20 m × 0.25 mm i.d., 0.15 µm 100% dimethyl PS.
• Injection: 0.5–2 µL split injection, split flow 20 mL/min, injector at 250 °C.
• Carrier gas: hydrogen for FID or helium for MS at 60–80 kPa constant pressure.
• Oven program: 60 °C (0.5 min), 30 °C/min to 110 °C, 50 °C/min to 300 °C.

Main Results and Discussion

Automation delivered reproducible derivatization and extraction conditions with a total cycle time of ~10 min per sample. Transesterification reached completion for phthalates, epoxy oils, and adipates within 45 s, with no significant saponification up to 240 s. Continuous verification flagged occasional reagent delivery failures, ensuring quality control. Up to 40 plasticizers were separated and quantified at levels below 0.1%.

Benefits and Practical Applications

• Fully automated workflow reduces manual labor and operator variability.
• Consistent derivatization ensures reliable quantification of phthalates and alternative plasticizers.
• High throughput supports routine monitoring of food contact materials and toy safety.
• Sum-parameter quantification allows screening for banned compounds at regulatory thresholds.

Future Trends and Opportunities

Advances may include integration with high-resolution MS for enhanced selectivity, machine-learning–driven optimization of derivatization parameters, miniaturized autosampler modules for on-site testing, and expanded databases for emerging plasticizers in line with evolving regulations (e.g., RoHS, REACH).

Conclusion

The automated sample preparation and transesterification approach offers a robust, reproducible, and high-throughput solution for comprehensive analysis of plasticizers in PVC-based food contact materials and toys, facilitating regulatory compliance and consumer safety.

References

• [1] G. McCombie et al., Eur Food Res Technol 235 (2012) 129–137.
• [2] Directive 2005/84/EC, European Parliament and Council, Dec. 14, 2005.
• [3] Directive 2011/65/EU, European Parliament and Council, June 8, 2011.
• [4] S. Biedermann-Brem et al., Food Additives and Contaminants 22 (2005) 1274–1284.