GC/MS Analysis of Ethanol in Low Alcohol Beer on SUPELCOWAX 10 after Headspace SPME using a 100 μm PDMS Fiber
Materials
SPME fiber
accessory
Headspace vial, screw top, rounded bottom (vial only)
volume 10 mL, clear glass vial, thread for 18, O.D. × H 22.5 mm × 46 mm, pkg of 100 eaMagnetic Screw Cap for Headspace Vials, 18 mm thread
PTFE/silicone septum (white PTFE/tranparent blue silicone), septum thickness 1.3 mm, pkg of 100 eaproficiency testing
reagent
CONDITIONS
sample/matrix
4 mL of diluted low alcohol beer sample in 10 mL headspace vial
SPME fiber
Pk/3 SPME Assy, 100 μm, PDMS FS 24 ga Auto (Red) (57301)
extraction
headspace at 40°C for 2 min, agitation at 250 rpm
desorption process
250 °C, 3 min, split 10:1
sample preparation
sample equilibrated prior to extraction for 7 min at 40°C, with agitation at 250 rpm
column
SUPELCOWAX 10, 30 m x 0.25 mm I.D., 0.25 μm (24079)
oven
40 °C (5 min), 8 °C/min to 70 °C, 20 °C/min to 250 °C, held for 5 min
inj. temp.
250 °C
detector
MSD
MSD interface
250 °C
scan range
m/z 25-300
carrier gas
helium, 1 mL/min constant flow
injection
split, 10:1
liner
0.75 mm I.D. SPME
Description
Analysis Note
Traditional methods for determination of alcohol in beverages include specific gravity and gas chromatography (GC). Specific gravity may not be able to accurately measure levels in beverages with low alcohol content, below 1%. GC is a better approach because it does not have this limitation. However, direct injection of samples containing sugars or other nonvolatile matrix components can foul the GC instrument. This drawback of GC can be overcome by sampling the headspace over the sample using solid phase microextraction (SPME), The method shown here was developed specifically for the determination of ethanol in low alcohol content samples, and was used to analyze a reference material of low alcohol beer. The sample had a certified value of 0.505% alcohol by volume (% ABV). Using headspace SPME, the average value measured was 0.495% ABV, representing 97% accuracy.
Other Notes
SPME Sample pretreatment: Dilute 400 uL of sample to 4 mL with 0.1M sodium phosphate buffer ( pH 7) containing 25% NaCl
Legal Information
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