ISQ User Guide - Write Frame of Mind

Changing the Column
The ISQ ships with a factory-tested 15 m x 0.25mm i.d. TR-SQC column, which the Field
Service Engineer uses to qualify the instrument. However, once it gets dirty, you cannot
purchase a new one, so you need to install a column that accommodates the type and quantity
of samples you will be running. You should choose a column that will give you the best
possible resolution, analysis speed, and quantitation.
When determining the type of column for your particular needs, here are a few things to
consider:
• Column Material—Columns made out of fused silica are economical and widely used.
Columns made out of this material have a wide range of stationary phases and are
available in many sizes that can be used with a mass spectrometer.
Large diameter columns made of steel are widely used in process gas analysis, but they are
not typically used on mass spectrometers. There are also metal-clad, fused silica columns,
which have the advantages of fused silica, but the metal makes them resistant to breakage.
These columns are less common and more expensive.
• Stationary Phase—The stationary phase is the most important consideration when
selecting a column. The interaction between the stationary phase and the analyte
determines how well the analytes separate from each other (resolution) and also affects
how quickly the separation occurs (analysis time). Choose a stationary phase that is
compatible with the nature of your analytes and the maximum GC oven temperature you
are going to use.
• Internal Diameter—The smaller the diameter of the column, the better the separation.
However, smaller diameter columns do not have as much capacity for matrix or analytes.
As a result, smaller diameter columns are subject to overloading, which leads to retention
time shifts and peak shape changes. Larger diameter columns can accept larger
concentrations of material, but will require longer columns or slower GC oven
temperature ramps (which increases the analysis time) to match the separation power of
shorter columns. Typical column sizes for GC/MS have inside diameters (ID) of
0.25 mm. Smaller ID columns, such as the 0.18 and 0.10 mm, are becoming increasingly
popular. Additionally, 0.32 and 0.53 mm ID columns are commonly used.
Thermo Scientific ISQ User Guide 1
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