312 / 413
•
10
•
2007.01
Superior Chromatography for Semivolatile Organics
Using the Rtx®-5Sil MS Capillary GC Column
by Robert Freeman, Environmental Innovations Chemist
Rtx®-5Sil MS Column (fused silica)
(Crossbond
®
, selectivity similar to 5% diphenyl/95% dimethyl polysiloxane)
ID df (µm)
temp. limits
length cat. #
price
0.25mm 0.25 -60 to 330/350°C 30-Meter 12723
$470
• Superior resolution of benzo(b)- and benzo(k)fluoranthene.
• Symmetric peaks and excellent responses for phenols.
• Excellent thermal stability and exceptionally low bleed.
GC/MS analytical methods for semivolatile com-
pounds, such as U.S. Environmental Protection
Agency Method 8270D and equivalent methods in
other countries, cover a broad range of environ-
mental pollutants. The target lists often include
complex mixtures of acidic, basic, and neutral ana-
lytes. Further, the sample extracts often contain
problematic matrix interferences. These factors,
coupled with the increasing need for lower detec-
tion limits, place significant demand on the ther-
mal stability, inertness, and efficiency of the ana-
lytical column.
Restek chemists designed the Rtx®-5Sil MS capil-
lary column to address the challenging demands of
semivolatiles analysis. Phenyl rings in the polymer
backbone of the stationary phase stiffen the silox-
ane chain, preventing thermal breakdown and
reducing bleed. The content of this aryl functional-
ity has been adjusted so that selectivity is similar,
but improved, compared to that of conventional
5% diphenyl/95%dimethyl phases. The silarylene
polymer not only exhibits improved thermal stabil-
ity and reduced bleed, it has increased separation
for aromatic isomers benzo(b)- and benzo(k)fluo-
ranthene – as shown in Figure 1.
Surface activity in a column is revealed by the
response factors for active analytes, such as 2,4-
dinitrophenol (acidic) and pyridine (basic). Most
column manufacturers struggle to attain adequate
responses and good peak shapes for such analytes.
Our unique deactivation process for the Rtx®-5Sil
MS silarylene phase assures unsurpassed inertness
and excellent responses for these active analytes –
note the response for 2,4-dinitrophenol in Figure
2, and for many other semivolatiles in Figure 3.
Featuring an optimized stationary phase, inher-
ently low bleed, and proprietary deactivation,
Rtx®-5Sil MS columns overcome the inherent
problems associated with semivolatiles analyses. If
you are performing these analyses, you can simpli-
fy life in your laboratory – rely on these new
columns to help you obtain consistent results.
Figure 1
Superior resolution of benzo(b)fluoranthene,
benzo(k)fluoranthene, and benzo(a)pyrene (10μg/mL).
Figure 2
Excellent response for 2,4-dinitrophenol (10μg/mL).
For conditions see Figure 3.
For conditions see Figure 3.
GC_EV00900A
GC_EV00900B
RF = 0.182
83% resolution
Excellent peak shape
and resolution!
m/z=252
m/z=126
m/z=184
m/z=107