Chemical Analysis of Wine with HS-SPME and GC-TOFMS for Target Screening and Non-Target Characterization and Comparison

Importance of Topic

Volatile aroma compounds significantly influence wine quality, consumer acceptance, and market value.
The ability to detect trace faults such as cork taint, alongside comprehensive profiling of desirable flavor and aroma constituents, is essential for quality control, authenticity verification, and product optimization in the wine industry.

Objectives and Study Overview

The primary aim was to apply headspace solid-phase micro-extraction (HS-SPME) coupled with gas chromatography–time-of-flight mass spectrometry (GC-TOFMS) for both targeted screening of 2,4,6-trichloroanisole (TCA) at parts-per-trillion levels and non-targeted characterization of volatile compounds.
A comparison between fresh and oxidized wine samples was performed to illustrate differentiation capabilities and to evaluate an extension to comprehensive two-dimensional gas chromatography (GC×GC) for enhanced separation and sensitivity.

Methodology

• Sample Preparation: Shiraz wine samples (10 mL) were spiked with TCA at 5 ppt–10 ppb, or exposed to air for two weeks to generate oxidized samples; salt (3 g) was added prior to HS-SPME.
• HS-SPME Conditions: Extraction at 65 °C (5 min equilibration, 30 min extraction) using a 2 cm DVB/CAR/PDMS fiber.
• Chromatographic Program: Initial oven temperature 40 °C (2 min), 5 °C/min to 200 °C, then 20 °C/min to 300 °C (1 min hold); helium carrier gas at 1 mL/min.
• Detection: TOFMS acquisition at 15 spectra/s over m/z 33–500 for full-range library searchable spectra.

Instrumentation

• Gas Chromatograph: Agilent 7890 with MPS2 autosampler (fiber desorption at 250 °C, splitless).
• Column: Rxi-5ms, 30 m × 0.25 mm i.d., 0.25 µm film thickness (Restek).
• Mass Spectrometer: LECO Pegasus® HT with 250 °C ion source and 260 °C transfer line.
• GC×GC Extension: Rxi-17Sil MS secondary column (0.6 m × 0.25 mm i.d., 0.25 µm) with thermal modulator (2 s modulation periods).

Main Results and Discussion

• Targeted TCA Screening: Achieved detection at 5 ppt with calibration linearity (R² = 0.9999) and < 8% quantitation error at 50 ppt in matrix.
• Non-Targeted Profiling: Hundreds of volatile and semi-volatile analytes (esters, acids, alcohols, aromatics, sulfur compounds) were detected, each contributing to aroma complexity.
• Differentiation of Fresh vs. Oxidized Samples: Data processing and extracted ion chromatograms revealed specific markers—sulfur derivatives up to 9-fold higher in fresh wine and aldehydes elevated in oxidized samples—hidden in total ion chromatograms.
• GC×GC Benefits: Two-dimensional separation increased peak capacity, improved resolution of coeluting compounds, and enhanced signal-to-noise through thermal focusing, enabling detection of additional analytes below one-dimensional thresholds.

Benefits and Practical Applications

• Quality Control: Sensitive screening for cork taint and other faults at sensory threshold levels.
• Flavor and Aroma Profiling: Comprehensive non-targeted characterization supports product development and authenticity verification.
• Comparative Studies: Differentiation of processing or storage conditions (fresh vs. oxidized) for shelf-life and spoilage assessments.
• Method Versatility: Single-injection data can be mined for targeted quantitation and non-targeted discovery without additional sample runs.

Future Trends and Opportunities

Continued advancements in comprehensive GC×GC coupled with high-resolution time-of-flight and orbitrap mass analyzers will further enhance separation power and identification confidence.
Integration of chemometric and machine learning approaches can automate pattern recognition for rapid classification and fault detection.
Coupling sensory-directed analysis (GC-olfactometry) with advanced instrumentation will bridge analytical data to perceived aroma impact.
Miniaturized sampling devices and real-time monitoring platforms hold promise for in-field and at-line quality assurance.

Conclusion

The combined HS-SPME GC-TOFMS approach effectively quantifies trace TCA and delivers extensive non-targeted volatile profiles in wine matrices.
Extending to GC×GC further resolves complex mixtures, increases detection sensitivity, and uncovers subtle compositional differences, demonstrating a powerful workflow for routine quality control, research, and product development in enology.