1. American Chemical Society, Fall 2012
Challenges of ionic liquid GC column for beer and wine volatile analysis
Yanping L. Qian, Hui Feng, Michael C. Qian*
Oregon State University, Corvallis, OR U.S.A. Phone , fax:
Abstract
Introduction to Ionic Liquid Chromatography
Structure of Ionic Phase
The volatile composition of beer and wine is best analyzed by GC or GC-MS with a polar capillary column such as Wax or FFAP stationary phase column, due to high concentrations of alcohols and volatile fatty acids in the sample. However, such phases are not thermally stable and resulting in high background noise at elevated temperature. It is desirable to have a column with high polarity and thermal stability for volatile analysis using GC-MS. Ionic liquids are a class of compounds consists of organic cations associated with inorganic or organic anions. They are very polar and have low volatility. Several ionic liquid (SLB) capillary GC columns were studied for the suitability of volatile analysis in beer and wine. The results showed that SLB columns can separate most volatile compounds effectively, and have very good thermal stability. However, the SLB columns tested have too strong interactions with acids (octanoic  and decanoic acids), resulting in poor chromatography for these compounds.
Materials and Methods
From Sigma-Aldrich
Beer sample preparation: Beers were manufactured at Oregon State University Pilot Plant, different commercial hops were obtained and used for brewing
Results
2. Sample extraction by SBSE
The stir bar was dried with kimwipe and placed in glass insert
10mL beer was 1 : 1 diluted with Milli-Q water
Samples were extracted with SBSE for 3 h at rpm.
3. Thermal desorption-GC-MS Analysis
TDU: Initial Temp. 20°C, delay time 0.5 min, rate 120°C/min, final temp. 250°C, hold time 2 min, desorption mode splitless
PVT-Cis 4: Solvent vent mode, vent flow 50mL/min, vent pressure 5psi, purge flow to split vent 50mL/min at 4 min.
Cis initial temp. -80°C, rate 10°C/S, final temp.250°C, hold 54 min,
GC-MS: ZB-Wax plus (30m x 250 µm x 0.25 µm), SLB-IL59 (30m x 250 µm x 0.2 µm), 2 mL/min flow rate, 1:1 split to MSD Oven 35°C for 4 min, rate 4°C/min, final temp. 230°C, final time 5 min
Conclusion
Volatile Compounds in alcoholic beverage can be easily analyzed by PDMS-SBSE-GC-MS
SLB columns can separate most volatile compounds effectively, and have very good thermal stability.
However, the SLB columns tested have too strong interactions with acids (octanoic  and decanoic acids), resulting in poor chromatography for these compounds.
Chromatography can be improved by extracting the sample at basic condition using SBSE
1. Ethyl acetate (3.793); 2. Isoamyl acetate (9.991); 3. Isoamyl alcohol (13.274); 4. Ethyl hexanoate (13.709); 5.Ethyl octanoate (20.680); 6.Ethyl decanoate (26.677); 7. 2-Phenylethyl acetate (31.348); 8. Phenyl ethyl alcohol (33.704); 9. Nerolidol 2 (37.029); 10. Octanoic acid (37.372); Methoxy-4-vinylphenol (40.297); 12. Decanoic acid (42.219); 13. Dodecanoic acid (46.588).