Restek-2015

www.restek.com

Figure 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