Highly Sensitive Analysis of Sulfur Compounds in Beer Using the Trap Mode of a Headspace Sampler

Significance of the Topic

Volatile sulfur compounds contribute substantially to beer aroma and quality despite existing at trace levels
Accurate quantification is essential for product consistency and sensory evaluation
Advancements in headspace sampling and detection techniques enhance analytical sensitivity

Objectives and Study Overview

The study aimed to evaluate the trap mode of a headspace sampler coupled with a sulfur chemiluminescence detector (SCD) to improve detection of volatile sulfur compounds in beer samples
Comparison between conventional loop mode and trap mode was performed using two beers brewed with different yeasts

Used Instrumentation

GC Nexis GC-2030 gas chromatograph combined with SCD-2030 detector
HS-20 NX headspace sampler operated in trap and loop modes
Tenax TA as the sorbent material for trap mode preconcentration

Methodology

Samples consisted of two test beers containing 3 g NaCl and 3 g beer
Headspace gas underwent five sequential injections into a trap tube at 10 °C followed by thermal desorption at 250 °C
Chromatographic separation was achieved on a DB-1 column (60 m × 0.32 mm, 5 µm)
Detection employed a sulfur chemiluminescence detector with controlled flows of H2, N2, O2 and O3

Results and Discussion

Trap mode provided a 6 to 20 fold increase in signal to noise ratio compared to loop mode for key sulfur compounds
Compounds undetectable in loop mode were clearly identified in trap mode chromatograms
Significant difference in S-methylthioacetate levels was observed between the two beers with yeast A showing higher concentration
S-methylthioacetate likely underlies aroma differences linked to yeast strain selection

Benefits and Practical Applications

• Enhanced sensitivity for trace level volatile sulfur analysis
• Ability to conduct multi-injection preconcentration within a single vial
• Flexibility to switch between trap and loop modes based on sample requirements
• Elimination of helium carrier requirement by using nitrogen

Future Trends and Applications

Integration of automated trap mode workflows for high throughput quality control
Expanded use of trap mode preconcentration in other fermented beverages and food matrices
Development of advanced sorbent materials to target broader compound classes
Coupling with other detectors for multi dimensional odor profiling

Conclusion

The trap mode of HS-20 NX combined with SCD detection significantly improves analysis of volatile sulfur compounds in beer
This approach enables detection of previously inaccessible trace analytes and reveals aroma differences linked to yeast strain
The method offers a robust tool for research and quality control in beverage industries

Reference

1. Identification and Determination of S-Methyl Thioacetate in Beer, Nippon Nogeikagaku Kaishi, Vol 54, No 9, 1980