DETERMINATION OF AROMATIC ALCOHOLS IN BEER BY SOLID PHASE EXTRACTION AND DETECTION WITH GAS CHROMATOGRAPHY IN COMBINATION WITH MASS SPECTROMETRY (GC-MS) Part I. – Creation and validation of the analytical method

Importance of the topic

Beer contains dozens of volatile compounds that shape its aroma and flavor profile. Among these, aromatic alcohols such as 2-phenylethanol, guaiacol and its derivatives, tyrosol and tryptophol have significant sensory impact even at low concentrations. Reliable quantification of these compounds is essential for quality control, research into beer flavor formation and optimization of brewing processes.

Objectives and article overview

The study aimed to develop and validate a fast, robust analytical method for determining key aromatic alcohols in beer. The focus was on creating a selective isolation procedure using solid-phase extraction (SPE) coupled with sensitive detection by gas chromatography–mass spectrometry (GC-MS). Performance characteristics such as linearity, precision, accuracy and detection limits were evaluated.

Methodology and instrumentation

The proposed workflow combines SPE on LiChrolut EN cartridges with GC-MS analysis in selected-ion monitoring (SIM) mode. Key steps include:

• Degassing beer and adjusting pH to 8.5 with NaOH
• Adding an internal standard (4-ethylphenol) and loading onto SPE
• Conditioning SPE with methanol and alkaline water
• Eluting analytes with ethyl acetate
• Concentrating eluate under nitrogen and injecting 1 µL into GC-MS

The GC-MS system (Trace GC Ultra – DSQ II) was equipped with either a 30 m RTx-5Sil MS or a 50 m CP-Sil 8 CB capillary column. Oven temperature programs were optimized for each column to achieve baseline separation.

Used instrumentation

• GC-MS: Trace GC Ultra – DSQ II
• Columns: RTx-5Sil MS (30 m×0.25 mm×0.25 µm) and CP-Sil 8 CB (50 m×0.25 mm×0.25 µm)
• SPE manifold with LiChrolut EN cartridges
• Vacuum pump and nitrogen concentrator
• Ultrasound bath, centrifuge, pH meter

Main results and discussion

The method exhibited excellent linearity (r > 0.995) over concentration ranges covering typical beer levels. Repeatability (RSD < 7%) and intralaboratory reproducibility (RSD < 15%) were satisfactory for all analytes. Limits of detection ranged from 0.0001 to 0.005 mg/L in sample. The RTx-5Sil MS column provided sharper peaks and reduced analysis time compared to the longer CP-Sil 8 CB column, especially for tyrosol and tryptophol. Application to commercial lagers and nonalcoholic beers confirmed the method’s sensitivity and selectivity, with SIM mode significantly improving signal-to-noise ratios.

Benefits and practical application

This SPE-GC-MS procedure offers brewers and analytical laboratories a reliable tool for:

• Routine monitoring of sensory-active aromatic alcohols
• Profiling beer aroma for product development
• Comparative studies across beer styles and processing conditions

The fast sample preparation and low detection limits support quality assurance and research needs.

Future trends and potential applications

Emerging directions include:

• Automation of SPE for higher throughput
• Use of isotope-dilution mass spectrometry for absolute quantification
• Integration with solid-phase microextraction (SPME) for comprehensive volatile analysis
• Extension to novel beer styles, specialty malts and dealcoholized products

Advances in column technology and tandem MS detection will further enhance selectivity and lower quantification limits.

Conclusion

The validated SPE-GC-MS method provides a robust, sensitive and practical approach to quantify key aromatic alcohols in beer. Its strong performance in terms of linearity, precision, accuracy and low detection limits makes it well suited for brewery quality control, sensory research and product optimization.

References

• Čulík J. et al. Kvasny Prum. 55, 2009; Determination of aromatic alcohols in beer by SPE and GC-MS. Part I: Method development and validation.
• Dufour J-P. et al. J. Am. Soc. Brew. Chem. 52, 2002; Stable isotope dilution analysis of beer aromatic alcohols.
• Saegusa K. et al. Biomed. Chromatogr. 7, 1993; GC-MS determination of guaiacol and catechol.
• Vanderhaegen B. et al. Monatsschr. Brauwiss. 58, 2005; Purge and trap GC-MS of beer flavor compounds.
• Almeida C. et al. J. Agric. Food Chem. 54, 2006; 1H NMR profiling of beer composition.