Determination of Volatiles in Liquors by GC-FID with Dual Acquisition System

Significance of the Topic

The precise profiling of volatile constituents in alcoholic liquors is vital for ensuring product quality, flavor consistency and consumer safety. Unwanted volatiles, particularly toxic compounds like methanol, must be accurately detected and quantified to comply with regulatory limits and maintain beverage integrity.

Objectives and Study Overview

This study aimed to develop a robust gas chromatography–flame ionization detection (GC-FID) method using a dual acquisition system to separate and quantify a broad range of volatile compounds in high-ethanol samples. The approach focused on minimizing analysis downtime while achieving high sensitivity and linearity.

Materials and Methods

Calibration standards for two mixtures of target compounds were prepared in 40 % ethanol matrix at concentrations of 30, 150, 300 and 600 ppm (v/v). All standards and liquor samples were spiked with 300 ppm 3-pentanol as an internal standard. To prevent backflash caused by water expansion during injection, a reduced volume of 0.5 ml was used together with Shimadzu’s High Pressure Injection feature.

Used Instrumentation

• Nexis GC-2030 gas chromatograph equipped with Dual AOC-20i/s autosampler
• Two split injection ports and two flame ionization detectors (FID)
• Rtx-502.2 column (30 m × 0.25 mm ID, 1.4 µm film) for Mixture 1
• SH-Stabilwax column (30 m × 0.32 mm ID, 1.0 µm film) for Mixture 2

Main Results and Discussion

Both mixtures achieved baseline separation within 18 min (Mixture 1) and 8 min (Mixture 2). Internal standard calibration curves exhibited excellent linearity with R2 values above 0.9997 for all analytes. Quantitation of two commercial liquors demonstrated detection of fusel oils, esters and aldehydes at levels from single-digit ppm to over 1000 ppm. Methanol was measured at 177.5 ppm in Liquor 1 and 37.7 ppm in Liquor 2, both well below the EU limit of 4000 ppm for traditional spirits.

Benefits and Practical Applications

• Reduced analysis downtime by simultaneous dual-column switching.
• High accuracy and linearity for a wide concentration range of volatiles.
• Effective prevention of backflash in water-rich samples.
• Applicability for routine quality control and regulatory compliance in beverage production.

Future Trends and Possibilities

Further advancements may include integration of mass spectrometric detection for enhanced compound identification and quantitation at trace levels. Automation of sample preparation and data processing will improve throughput. The methodology could be extended to non-alcoholic beverages and fermentation monitoring in bioprocessing.

Conclusion

The dual acquisition GC-FID approach on the Nexis GC-2030 provides a reliable, high-throughput solution for comprehensive volatile analysis in high-ethanol liquors. It ensures rapid separations, robust quantitation and minimal downtime, making it an ideal tool for industrial quality control and safety assessments.

Reference

1. Dragone C, Pinto C, Vicente AA, Teixeira JA. Characterisation of volatile compounds in alcoholic beverage produced by whey fermentation. Food Chemistry. 2009;112(4):929–935.
2. Paine A, Dayan A. Defining a tolerable concentration of methanol in alcoholic drinks. Human & Experimental Toxicology. 2001;20(10):563–568.