Over the past year, I have had the opportunity to work with some great breweries. In those conversations, I came across a consistent issue; the analysis of Beer Volatiles represents a significant hurdle due to sample complexity. After joining the American Society of Brewing Chemists (ASBC), I realized this is a critical test in brew labs [1]. We’re here to help, hence we decided to start this series.
Our first challenge is proper sample preparation and chromatographic separation. Since these compounds of interest are volatile (see Table 1), they will not be retained well on a column with a thin film. Additionally, these compounds are polar, so it is important to make sure the correct stationary phase is selected. So, how do we find a column with the right polarity and column dimensions? Easy! We go to the Restek ProEZGC Chromatogram Modeler!
Table 1: Beer Volatiles
|
# |
Compound |
|
1 |
Acetaldehyde |
|
2 |
Ethanol |
|
3 |
Ethyl Acetate |
|
4 |
n-Butanol |
|
5 |
Isoamyl Alcohol |
|
6 |
Isoamyl Acetate |
After adding our compounds of interest into the compound table, we hit “solve,” and are given several column options. These include the Rtx-502.2, Stabilwax, and Rxi-624Sil MS. Out of these, I recommend the Rxi-624Sil MS for its selectivity, inertness, low bleed, and compatibility with the mass spec. In ProEZGC, you can select column dimensions and change the method parameters to improve the chromatography to your liking. After selecting the 30m x 0.25mm x 1.4µm dimension, I did some method optimization and came up with the method shown below.
As you can see, the modeled chromatogram for this method looks pretty good! We have great resolution between acetaldehyde and ethanol, and the remaining compounds of interest are separated. ProEZGC Chromatogram modeler is a great tool for starting a new application! Stay tuned for ProEZGC to be put to the test with some real beer samples! Of course, that is assuming the samples make it safely to the lab…
References
- American Society of Brewing Chemists, “HEADSPACE GAS CHROMATOGRAPHY–FLAME IONIZATION DETECTION ANALYSIS OF BEER VOLATILES (Beer-48),” pp. 1-4, 2012.
