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VIEW ARTICLE DOI: 10.1094/ASBCJ-54-0228
Quantitative Analysis of Volatile Sulfur Compounds in Beer Using a Membrane Extraction Interface. A. Dercksen, The South African Breweries Ltd., Research & Development Dept., P.O. Box 782178, Sandton, South Africa 2146; J. Laurens, Department of Chemistry, University of Pretoria, Pretoria, South Africa 0001; P. Torline and B. C. Axcell, The South African Breweries Ltd., Research & Development Dept., P.O. Box 782178, Sandton, South Africa 2146; and E. Rohwer, Department of Chemistry, University of Pretoria, Pretoria, South Africa 0001. J. Am. Soc. Brew. Chem. 54(4):228-233. Accepted August 27, 1996.
Improved quantitation
of volatile
sulfur compounds
in beer using
membrane extraction
is demonstrated.
The membrane
consists of
a silicone tube
(300 mm ×
0.29 mm i.d.
× 0.6 mm
o.d.). The tube,
purged with
helium for flame
photometric
detection or
with nitrogen
for sulfur chemiluminescence
detection is
placed directly
in the beer,
and the sulfur
compounds that
permeate through
the walls of
the tube are
collected cryogenically
and thermally
desorbed onto
a capillary
gas chromatographic
column for analysis.
Replicate analysis
of a single
sample shows
a coefficient
of variation
(CV) of <5%,
whereas replicate
analysis of
multiple samples
from the same
batch gave a
CV of approximately
10%. Recovery
of sulfur compounds
is linear over
the range normally
expected in
beer. The use
of the technique
to investigate
changes in sulfur
compounds in
beer over time
is also discussed.
Keywords: Beer
analysis, Cold
trap, Flame
photometric
detector, Gas
chromatography,
Membrane interface,
Sulfur chemiluminescence
detector, Sulfur
compounds, Volatiles.
La
optimización
de la cuantificación
de compuestos
de azufre en
cerveza usando
extracción
por membrana
es demostrado.
La membrana
consiste en
un tubo de silicona
(300 mm ×
0.29 mm i.d.
× 0.6 mm
o.d.). El tubo,
purgado con
helio o nitrógeno
es colocado
directamente
en la cerveza
y los compuestos
de azufre que
permean a través
de las paredes
del tubo son
colectado cryogenicamente
y desorbidos
dentro de una
columna capilar
para el analisis
por cromatografía
de gases. El
analisis por
duplicado de
una sola muestra
presenta un
coeficiente
de variación
(CV) de <5%
mientras que
el analisis
de muchas muestras
de un mismo
lote da un CV
de ± 10%.
La recuperación
de los compuestos
de azuf re es
lineal sobre
el orden normalmente
esperado en
cerveza. El
uso de la técnica
para investigar
los cambios
en los compuestos
de azufre en
cerveza con
el tiempo es
también
discutido.
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