3
Column Modules
30
User Guide
To Select In and Out Column Segments
The short column used to connect the GC inlet to the LTM column is called the
In segment
when configuring the column on the GC. This column can also be referred to as a guard
column, transfer line, or retention gap (depending on its uses). Similarly, the piece of column
used to connect the GC detector (or other hardware) to the LTM column exit will be called the
Out segment
.
When selecting column material for use as the In segment or Out segment, consider the
following:
•
In general, use uncoated deactivated fused silica of the same id as the analytical column.
Using the same id column can help avoid peak broadening and other issues.
•
Cut a piece of fused silica that is long enough to let you open the LTM oven door at least
half-way, plus some length to allow for several trimmings.
•
Typically use a length of column 40 to 50 cm long.
•
If possible, avoid very long lengths. While the GC oven typically remains isothermal, it is still
best to avoid a segment that touches the GC oven walls when possible.
•
In some cases, using shorter In and Out column segments provides better results. By using
shorter segments, from 25 cm to 27 cm long, you can minimize the chance of cold spots
caused by these columns touching the GC oven walls.
Always measure the actual segment lengths used. Enter these measurements when
configuring the LTM column in the GC.
