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26
www.restek.comFigure 2:
Compared to conventional GC columns, Rxi® columns show excellent inertness and
produce good peak shape and reproducible retention for challenging compounds.
GC COLUMNS |
HIGH-PERFORMANCE Rxi® COLUMNS
Rxi® Columns Overview
Improved Response for Difficult Compounds
Another reason column inertness is important for trace-level analysis is that many acidic, basic, and polar com-
pounds will tail significantly and become difficult to analyze if the column contains active sites. The remarkable
neutrality of Rxi® columns solves this problem and allows a wide range of compounds to be analyzed with high
sensitivity, often on a single column. All Rxi® columns are exceptionally inert as demonstrated in Figure 3 by
high response factors for both pyridine (basic) and 2,4-dinitrophenol (acidic). Rxi® columns reliably produce
highly symmetric peaks and improved responses for difficult compounds, indicating greater inertness than
columns produced by other manufacturers (Figure 4).
What are “Sil” Rxi® Columns?
By combining arylene chemistry with Rxi® technology, Restek has developed a subgroup of Rxi®
columns with exceptional thermal stability. These columns are produced by incorporating phenylene
groups into the polysiloxane backbone, forming silarylene copolymers. As a result of this modification,
these columns, which are distinguished by a “Sil” naming convention, have greater thermal stability
than their conventional counterparts. Four Sil columns are currently available: Rxi®-5Sil MS, Rxi®-624Sil
MS, Rxi®-35Sil MS, and Rxi®-17Sil MS; these columns have the same polarity as their conventional
counterparts, but differ in selectivity. Higher thermal stability results in lower bleed, which can make
these columns useful for MS applications or when increased sensitivity is required.
2.10 2.20 2.30 2.40 2.50 2.60 2.70 2.80
Time (min)
5ng,2.26min
2.5ng,2.28min
1ng,2.32min
A: Pyridine on non-Rxi® column
Retention times vary with
concentration; poor peak
shape requires manual
integration and additional
review.
2.25 2.30 2.35 2.40 2.45 2.50 2.55 2.60
Time (min)
5ng,2.39min
1ng,2.40min
0.5ng,2.41min
Predictable retention
times, regardless of
concentration; easy,
accurate integration.
B: Pyridine on Rxi® column
extracted ion
chromatogram, m/z 79
Figure 3:
An Rxi® column gives the best overall performance for both basic and
acidic compounds.
Comparison of .
30 m x 0.25 mm ID, .
0.25 µm columns.
0.000
0.200
0.400
0.600
0.800
1.000
Rxi-5ms
Competitor A
Competitor B
Competitor C
Competitor D
Competitor E
Competitor F
2 ng pyridine
Response Factor (RF)
Column
Response Factor (RF)
0.000
0.050
0.100
0.150
0.200
0.250
0.300
Rxi-5ms
Competitor A
Competitor B
Competitor C
Competitor D
Competitor E
Competitor F
2 ng 2,4-dinitrophenol
Column
GC_EX01119
GC_EX01118