102 / 298
• 8 •
www.restekcorp.com✔
Stable, long-term storage of sulfur VOCs.
✔
More accurate sampling.
✔
Accessories available.
SilcoCan
®
Canisters
Ideal for Low-Level (1ppb-20ppb) Reactive
Sulfur Compounds
by Dave Shelow, Air Monitoring Innovations Chemist
The analysis of low-level sulfur volatile organic com-
pounds (VOCs) has become important because of
odor complaints near manufacturing sites and
refineries. Collection and measurement of these com-
pounds in the atmosphere is very difficult because of
their low concentration and high reactivity. These sul-
fur compounds not only can react with each other
but also with the vessels in which they are collected.
This results in low recoveries of compounds such as
hydrogen sulfide (H
2
S), methyl mercaptan (CH
3
SH),
ethyl mercaptan (C
2
H
3
SH), and dimethyl disulfide
(CH
3
SSCH
3
).
Tedlar bags traditionally have been used for collecting
sulfur VOCs; however, the stability of low-level
(100ppbv) sulfur VOCs is poor within 24 hours of
sampling.
1
Electropolished canisters (e.g., SUMMA
®
canisters) are excellent for storing VOCs in ambient
air; however, the sulfur compounds react with the
metal surface so these canisters are unsuitable for
collecting and storing low-level sulfur VOCs.
2
SilcoCan
™
air monitoring canisters, which feature a
Silcosteel
®
-treated surface, increase the storage stabil-
ity of low-level sulfur VOCs. We evaluated the stability
of sulfur VOCs within SilcoCan
™
canisters at very low
60m, 0.53mm ID, 7.0µm Rtx
®
-1 (cat.# 10193)
GC:
Agilent 5890GC;
Det.:
Sievers Model 355 SCD
Oven temp.:
30°C (hold 1.0 min.) to 180°C @
10°C/min. (hold 5 min.);
Flow rate:
8.5mL/min.
Sample:
1mL sample loop of 11ppbv
Standards:
Dry standards were made by taking 2mL of a 100ppm stock sulfur standard and adding it to each precleaned and evacuated canister, then pressurizing to 30psig
with ultra-pure nitrogen. The resultant concentrations are listed in Applications Note #59347. Humidified standards were made by injecting the evacuated canisters with 100µL
of deionized water prior to adding the 2mL aliquot of stock standard. This resulted in 50% RH.
levels (1–20ppbv) for six days. A comparison study
of dry vs. humidified standards demonstrates the abil-
ity of SilcoCan
™
canisters to store low-level sulfur
VOCs in real-world conditions. The results showed
excellent stability of each of the low-level sulfur VOCs
in the dry and the humidified standards when using
SilcoCan
™
canisters. However, the electropolished
canisters exhibit rapid degradation of hydrogen sul-
fide, methyl mercaptan, and ethyl mercaptan during a
similar study (Figure 1).
When you need to perform sensitive air monitoring
analyses, use a SilcoCan
™
canister to collect and store
your samples.
✔
SilcoCan
™
Canisters
size (L)
cat.#
1
24112
3
24113
6
24114
15
24115
References
1. Quang Tran, You-Zhi Tang; Stability of Reduced Sulfur Compounds in Whole Air Samplers, 1994 AWMA/EPA International Symposium of Measurement of Toxic and Related Air Pollutants.
2. Hoyt, Steven; Longacre, Vivian; and Stroupe, Michale; Measurement of Oxygenated Hydrocarbons and Reduced Sulfur Gases by Full Scan GC/MS: EPA TO-14; Sampling and Analysis of Airborne Pollutants, Eric Winegar,
Lawrence Keith.
References not available from Restek.
for
more
info
For complete details on the analytical
system, request lit. cat.# 59347.
Dry SilcoCan
™
(n=18)
Humidified SilcoCan
™
(n=5)
Electropolished (n=2)
Figure 1
Stability data demonstrates the effectiveness of using SilcoCan
™
canisters to store low-level organic sulfur compounds in real-world conditions.