Corkiness in Wine - Trace Ana ly sis of 2,4,6-Trichloroanisole by Stir Bar Sorptive Extraction (SBSE) and Thermal Desorption GC/MS

Significance of the Topic

2,4,6-Trichloroanisole (TCA) is recognized as the principal compound responsible for cork-induced off-flavors in wine, even at concentrations as low as 15–20 ng/L. Reliable detection and quantification of TCA in wine samples are critical for quality control, regulatory compliance and prevention of spoilage. Conventional methods often require extensive solvent extraction or direct cork analysis, making a solvent-free, direct wine analysis approach highly desirable.

Objectives and Study Overview

This study evaluates a novel solvent-free extraction technique—Stir Bar Sorptive Extraction (SBSE)—combined with thermal desorption and GC/MS for trace analysis of TCA in wine. The aim is to assess sensitivity, linearity, recovery and applicability to real wine samples, comparing performance with established SPME approaches.

Materials and Methods

Sample preparation involved placing 10 mL of wine into a headspace vial, adding a PDMS-coated stir bar (55 µL coating volume), sealing and stirring for 30–120 minutes. After extraction, stir bars were rinsed, dried and thermally desorbed at 200 °C in a cryogenically cooled programmable temperature vaporization inlet. An Agilent 6890 GC coupled to a 5973 MSD performed analysis under both full scan and selected ion monitoring (SIM) modes.

Used Instrumentation

• SBSE stir bar (Twister, 10 mm, 55 µL PDMS)
• Thermal desorption unit (TDS 2) and programmable temperature vaporization inlet (CIS 4)
• Gas chromatograph (Agilent 6890) with HP-5 column (30 m × 0.25 mm, 0.25 µm film)
• Mass selective detector (Agilent 5973 MSD)

Main Results and Discussion

Calibration in total ion chromatogram mode exhibited linear responses from 10 to 100,000 ng/L (r2=1.000). In SIM mode, linearity extended down to 1 ng/L. SBSE provided phase ratios below 200, yielding recoveries above 50% for compounds with octanol–water coefficients (K(o/w)) as low as 200—over 100-fold sensitivity improvement compared to fiber SPME. Analysis of wine samples revealed TCA levels ranging from 0.3 to 160 ng/L. Clean mass spectra and enhanced signal-to-noise in SIM mode enabled reliable quantitation at sub-ppt levels.

Benefits and Practical Applications

• Solvent-free extraction minimizes toxic waste and aligns with green analytical chemistry principles.
• Direct analysis of wine simplifies workflow by eliminating solvent extraction or cork pre-treatment.
• High sensitivity and wide calibration range support quality control in winery and regulatory labs.
• Robust and reproducible, suitable for routine monitoring of off-flavor compounds.

Future Trends and Opportunities

Automation of SBSE coupled with high-resolution MS could enable multi-analyte screening in complex beverages. Miniaturization and integration with direct-injection MS may offer real-time monitoring of off-flavors. Expansion to other trace contaminants and aroma compounds promises broader applications in food, environmental and forensic analysis.

Conclusion

SBSE combined with thermal desorption GC/MS represents a powerful, environmentally friendly method for trace-level determination of TCA in wine. It overcomes limitations of existing techniques by delivering high sensitivity, minimal sample preparation and robust performance, making it ideally suited for routine wine quality assessment.

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