Stir Bar Sorptive Extraction from Food Simulating Solvents: Preliminary Studies

Importance of the Topic

The migration of packaging components into food is subject to strict regulatory requirements to ensure consumer safety. Detecting trace levels (1–50 ppb) of residual monomers, plasticizers, antioxidants and other indirect additives in complex food matrices is challenging. The FDA recommends simplified food simulants (water, 3 % acetic acid, 10 % ethanol, 95 % ethanol) for migration testing to minimize matrix effects and verify no-migration status.

Study Objectives and Overview

This work evaluates stir bar sorptive extraction (SBSE) combined with thermal desorption gas chromatography (TD-GC) for quantifying model and target compounds in FDA-prescribed food simulants. Key aims are to correlate analyte recovery with octanol-water partition coefficients (Kow), establish achievable detection limits, and demonstrate method suitability for regulatory migration testing.

Methodology

Model methyl esters (C4–C10) and representative packaging additives (aldehydes, aromatic esters, phthalates, styrene, benzophenone) were spiked at 0.1–100 µg/L into 10 mL of food simulants: water, 3 % acetic acid, 10 % ethanol and 95 % ethanol (diluted 1 : 10 in water). Samples were stirred for 90 min at ambient temperature with Gerstel Twister stir bars (24 µL PDMS). After extraction, stir bars were thermally desorbed directly into the GC inlet.

Použitá instrumentace

• Gerstel TDS 2/TDSA thermal desorption units with CIS 4 PTV inlet
• Gerstel Twister stir bars (24 µL PDMS phase)
• Agilent 6890 GC equipped with MSD or FID detectors
• 30 m HP-5 column (0.25 mm id, 0.25 µm film) with He carrier gas

Main Results and Discussion

• Analyte recovery correlates with log Kow. Compounds with log Kow > 2.3 (methyl hexanoate and above) achieved >30 % recovery in all simulants, enabling low-ppb detection.
• Short-chain esters (log Kow < 2.3) showed reduced recovery (often <50 %) in polar simulants; butanal was undetectable in 10 % ethanol and 3 % acetic acid at 100 µg/L.
• Estimated detection limits in water reached 0.1–1 µg/L for nonpolar esters; in 10 % ethanol and 3 % acetic acid limits were approximately 2× higher; in 95 % ethanol (after 1 : 10 dilution) limits were ~10× higher.
• Method precision was excellent (RSD < 5 % for most analytes), confirming reproducible SBSE performance across all simulants.

Benefits and Practical Applications

SBSE-TD-GC offers high sensitivity for nonpolar analytes, minimal interference from polar matrix components and straightforward sample preparation. Its compatibility with regulatory simulants makes it ideal for no-migration verification in QA/QC laboratories and development of new packaging materials.

Future Trends and Potential Applications

Advances may include novel sorptive coatings to target polar analytes, integration with high-resolution mass spectrometry for non-target screening, fully automated SBSE workflows for high throughput, and refined partitioning models to predict recovery across broader compound classes.

Conclusion

SBSE combined with thermal desorption GC provides a robust, sensitive and reproducible approach for assessing sub-ppb migration of nonpolar compounds in FDA-recommended food simulants. Kow-based partitioning enables accurate prediction of recovery and detection limits, supporting regulatory compliance and consumer safety.

References

1. FDA Recommendations for Chemistry Data for Indirect Food Additive Petitions. Chemistry Review Branch, Office of Premarket Approval, Center for Food Safety & Applied Nutrition, FDA, 1995.
2. Batlle R, Sanchez C, Nerin C. A Systematic Approach to Optimize Solid-Phase Microextraction Determination of Pesticides in Ethanol Water Mixtures Used as Food Simulants. Analytical Chemistry 71 (1999) 2417–2422.
3. Salafranca J, Batlle R, Nerin C. Use of Solid-Phase Microextraction for the Analysis of Bisphenol A and Bisphenol A Diglycidyl Ether in Food Simulants. Journal of Chromatography A 864 (1999) 137–144.
4. Pfannkoch E, Whitecavage J, Hoffmann A. Stir Bar Sorptive Extraction Enhancing Selectivity of the PDMS Phase. Pittsburgh Conference 2001, Poster 1861P.