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GC/MS Analysis of Ethanol in Low Alcohol Beer on SUPELCOWAX 10 after Headspace SPME using a 100 μm PDMS Fiber

GC/MS Analysis of Ethanol in Low Alcohol Beer on SUPELCOWAX 10 after Headspace SPME using a 100 μm PDMS Fiber suitable for GC/MS, suitable for solid phase microextraction (SPME)

Materials

SPME fiber

Product No.
Description
Pricing

SPME Fiber Holder

for use with CTC CombiPAL and Gerstel MPS2

accessory

Product No.
Description
Pricing

Inlet Liner, Direct (SPME) Type, Straight Design (unpacked)

pkg of 1 ea

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 ea

Magnetic Screw Cap for Headspace Vials, 18 mm thread

PTFE/silicone septum (white PTFE/tranparent blue silicone), septum thickness 1.3 mm, pkg of 100 ea

Molded Thermogreen® LB-2 Septa, with injection hole

diam. 11 mm, pkg of 50 ea

proficiency testing

Product No.
Description
Pricing

Beer (EtOH, low level)

BCR®, certified reference material

reagent

Product No.
Description
Pricing

Sodium phosphate dibasic

ReagentPlus®, ≥99.0%

Sodium phosphate monobasic

ReagentPlus®, ≥99.0%

standard

Product No.
Description
Pricing

Ethanol-d6

anhydrous, ≥99.5 atom % D

Ethyl alcohol, Pure

200 proof, anhydrous, ≥99.5%

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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