Using Three Types of Twister Phases for Stir Bar Sorptive Extraction of Whisky, Wine and Fruit Juice

Importance of the topic

Stir Bar Sorptive Extraction (SBSE) with tailored sorbent phases has emerged as a highly efficient, solvent-free sample preparation technique in analytical chemistry, particularly for flavor and aroma profiling in beverages. Understanding and expanding the range of extractable compounds—especially polar analytes that challenge conventional non-polar phases—enables more comprehensive qualitative and quantitative analysis of complex matrices such as whisky, wine, and fruit juice.

Objectives and Study Overview

This study compares three Gerstel Twister™ phases—ethylene glycol-silicone (EG-Silicone), polyacrylate (PA), and polydimethylsiloxane (PDMS)—to evaluate their performance in SBSE of whisky, white wine, and multivitamin juice. Key goals include generating qualitative flavor profiles, assessing extraction efficiency across a broad polarity range, and determining the pH stability limits of the novel EG-Silicone phase.

Methodology and Instrumentation

• Samples: Scotch whisky (40 % EtOH), sauvignon blanc white wine (13 % EtOH), multivitamin juice.
• SBSE Conditions: 5–10 mL sample (often diluted 1:1), 60 min extraction at room temperature, stirring at 1000 rpm.
• Twister Phases: EG-Silicone, PA, PDMS.
• Water Removal: Thermal Desorption Unit (TDU) in solvent-vent mode at low initial temperature (30–40 °C) to purge excess water.
• GC/MS Analysis: Agilent 6890N GC coupled to 5975B MSD under MAESTRO/ChemStation control; PTV inlet (CIS 4); non-polar ZB-5 and polar ZB-FFAP columns with tailored oven programs.
• pH Stability Tests: Wine samples adjusted to pH 3.6–6.8; aqueous standards adjusted to pH 2.8–11.0; Twisters conditioned post-extraction to evaluate blank peaks and phase integrity.

Main Results and Discussion

• EG-Silicone vs. PA and PDMS: EG-Silicone extracted a broader range of polar compounds (phenols, aromatic alcohols, acids, furans, esters) with up to one order of magnitude higher peak areas than PA or PDMS.
• Whisky Profiling: EG-Silicone yielded superior recovery of phenol, cresols, phenethyl alcohol, whisky lactones, and long-chain ethyl esters; PA captured polar aromatics but with lower sensitivity; PDMS excelled at non-polar esters but under-represented polar analytes.
• Multivitamin Juice: EG-Silicone detected nine furans and related compounds not observed with PDMS, plus stronger signals for acids and hydroxypyranones; PDMS favored monoterpene hydrocarbons.
• Terpene Extraction: PDMS performed better for non-polar monoterpenes (α-pinene, β-myrcene, d-limonene), whereas EG-Silicone improved recovery of more polar terpenoid alcohols (linalool, nerolidol).
• White Wine Flavor Profile: EG-Silicone extracted 30 tentatively identified compounds including organic acids, diols, and phenethyl derivatives, outperforming PDMS and PA for polar constituents; PDMS favored esters.
• pH Stability: EG-Silicone phase remains stable without phase breakdown between pH 3.5–10.0 in aqueous samples and pH 3.6–5.1 in wine. Extreme pH values induce siloxane or polyglycol background peaks and degrade extraction efficiency.

Benefits and Practical Applications of the Method

• Broad Polarity Coverage: Single-phase extraction of polar to non-polar analytes.
• Enhanced Sensitivity: Up to tenfold higher recoveries for key flavor compounds.
• Minimal Sample Preparation: Direct immersion SBSE simplifies workflow and automation.
• Versatile Beverage Analysis: Applicable to whisky QA/QC, wine authenticity studies, juice quality monitoring.

Future Trends and Application Possibilities

• Development of hybrid or sequential multi-phase SBSE protocols to maximize analyte coverage.
• Integration with high-resolution MS and real-time data analysis for rapid flavor fingerprinting.
• Expansion into other food, environmental, and biological matrices requiring polar analyte enrichment.
• Custom sorbent chemistries to target emerging contaminants and complex natural products.

Conclusion

The novel EG-Silicone Twister phase significantly enhances SBSE extraction efficiency for polar and non-polar compounds, facilitating richer flavor profiles in whisky, wine, and juice analysis. Careful pH control ensures phase integrity, while the combination or sequential use of EG-Silicone with PA and PDMS phases offers a comprehensive strategy for broad-spectrum analyte recovery.

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