APPENDIX
The Determination of Ethanol in Beer by Gas
Chromatography
Warning and Safety Precautions
For the recommended practices for the safe storage
and handling of compressed gases, refer to the BOC
Users' Guide. Both ethanol and n-butanol are flam
mable and must be kept away from sources of ignition.
n-Butanol is harmful by inhalation and also by adsorp
tion through skin.
SCOPE
The determination of ethanol in beer by gas liquid
chromatography using direct injection.
FIELD OF APPLICAT1ON
2.1 The method can be used to determine the etha
nol content of all beers and partly-fermented worts,
but not non-alcoholic beers, i.e. with ethanol contents
below 0.5% V/V. The method can be used to deter
mine the alcohol content of shandy. The method is
applicable to products with an ethanol concentration
between 0.5 and 8% V.V.
PRINCIPLE
3.1 The beer sample is de-gassed by filtration and
attemperated to 20°C.
3.2 The sample is diluted with known quantity
of n-butanol (as an internal standard).
3.3 The diluted liquid sample is injected into gas
chromatographic column, previously calibrated using
standard ethanol solutions.
3.4 The percentage of ethanol V/V in the sample
is calculated from the peak areas of the ethanol and nbutanol
peaks, using previously calculated calibration
factor.
REAGENTS
4.1 Unless otherwise stated, use only reagents of
recognized analytical grade and distilled water, or
water of equivalent purity.
4.2 Ethanol, absolute. Lower strengths may be
used provided the concentration is known.
4.3 n-Butanol, new batches must be checked chromatographically
to ensure that there are no inter
ferences with the ethanol peak.
4.4 n-Butanol (0.5% V/V), internal standard. Pip
ette 10 ml of n-butanol into a 2 litre volumetric flask
and dilute to litres with distilled water.
APPARATUS
5.1 Gas chromatograph, fitted with flame ionization
detector and an oven capable of operating isothermally
at 115°C.
5.2 Auto-sampler for the gas chromatograph—to
inject 0.5 or fi of liquid sample, OR a 10 (il gastight
positive displacement syringe.
5.3 Auto-diluter, capable of diluting to
10% 0.1%, OR ml grade bulb pipette, 20 ml
grade bulb pipette.
5.4 Computing integrator, OR Chart recorder an