8
Determining Trace Sulfur Compounds In Beer
Trace sulfur compounds that are generated during the fermentation process can affect
the taste and aroma ofmalted products such as beers. Several common volatile sulfur
compoundsmight be present in beer at ppb or ppm levels (Table 1).
1m, 0.75mm ID Sulfinert
™
tubing
Rt-XLSulfur
™
100/120mesh (cat.# 19806)
Conc.:
sulfur standard@ 20ppb each inCO
2
Inj.:
1cc sample loop, 6-portValco
®
valve
Carrier gas:
helium
Flow rate:
10mL/ min.@ ambient temp.
Oven temp.:
60°C to 260°C@ 15°C/min. (hold 5min.)
Det. sensitivity: SCD, attn. x 1
Det. temp.:
800°C
GC_FF00491
1. hydrogen sulfide
2. carbonyl sulfide
3. methyl mercaptan
4. ethyl mercaptan and/or
dimethyl sulfide
5. dimethyl disulfide
Volatile sulfur-containing compounds found in beer at ppm to ppb levels.
Accuratemeasurement of reactive sulfur compounds at these levels requires ahighly inert
chromatographic system. Restek's Rt-XLSulfur
™
micropacked column contains a modi-
fied divinyl benzene polymer packed into Sulfinert
™
tubing, and is specifically designed
formonitoringppb levelsof active sulfur compounds.TheRt-XLSulfur
™
columnexhibits
low bleed and thermal stability to 300°C. This column provides excellent resolution of
hydrogen sulfide, carbonyl sulfide and sulfur dioxide.
Sample introduction into the column is a critical step in obtaining accurate analytical
results for sulfur compounds. In this application, abeer headspace samplewas introduced
onto thecolumnusingaValco six-port samplingvalve fittedwitha1mL sample loop.The
valve, sample loop, and all other surfaces in the sample pathwaywere deactivated using
our Sulfinert
™
deactivation process. The use of Sulfinert
™
-treated hardware is critical to
achieving a 20ppb detection level for sulfur dioxide and the other target sulfur com-
pounds (Figure 8).
hydrogen sulfide
isopropyl mercaptan
carbonyl sulfide
methyl ethyl sulfide
methyl mercaptan
n-propyl mercaptan
ethyl mercaptan
t-butyl mercaptan
sulfur dioxide
sec-butyl mercaptan
dimethyl sulfide
diethyl sulfide
dimethyl disulfide
isobutyl mercaptan
carbon disulfide
n-butyl mercaptan
t-amyl mercaptan
Low levels of reactive sulfur compounds in CO
2
(i.e., 20ppb) easily can
be detected using anRt-XLSulfur
™
micropacked column and a Sulfinert
™
treated sample pathway.
Sample, Transfer, and Analyze Sulfur
Compounds at Parts-per-Billion Levels
Our exclusive Sulfinert
™
process is the
next generation of metals passivation
treatments, developed specifically for
deactivating metal surfaces that contact
organo-sulfur compounds. Untreated
stainless steel adsorbs or reacts with
hydrogen sulfide, mercaptans, and other
active sulfur-containing compounds.
Applied to a stainless steel surface, a
Sulfinert
™
layer prevents these com-
pounds, and other active compounds
(e.g., amines), from contacting the reac-
tive metal surface. Combine custom-
deactivated sample storage and transfer
components with stock Sulfinert
™
-treated
parts topassivate your entire system, and
obtain highly accurate information about
sulfur compounds in your samples.
Additional Important Features
Durable and flexible - will not crack
or flake.
Stable to 400°C.
Nomemory effects, as seenwith
polymeric surfaces.
Table 1
Figure 8
