User guide

Inlets 8
Advanced User Guide 261
6
Calculate the split ratio (split vent flow/column flow). Adjust
as needed.
7 If desired, turn Gas saver on. Set Saver time after the sample
has been introduced.
8 If Gas saver is on, be certain Auto prep run is On (see “Pre Run
and Prep Run” on page 171) or press [Prep Run] before
introducing the sample.
About the VI splitless mode
This mode is used to concentrate sample at the head of the GC
column during desorb. Purge timing delay must take into
consideration the volume of the loop or trap in the external
sampler plus the transfer line versus desorb/total flow rate.
Cryo focussing is required for very volatile samples in splitless
mode.
When you introduce a sample, the split valve remains closed
while the sample enters the interface and is transferred to the
column. At a specified time after the sample is introduced, the
split valve opens.
Splitless mode pneumatics
Before Pre Run When the GC is preparing for sample
introduction, total flow to the interface is measured by a flow
sensor and controlled by a proportional valve. Column flow is
controlled via back- pressure regulation. The split valve is open.