User guide

Inlets 8
Advanced User Guide 265
Setting parameters for the VI splitless mode
Mode: The current operating mode—splitless
Tem pe ratur e Actual and setpoint interface temperatures.
Column temperature must be low enough to cold trap the
volatile sample. Cryo focussing is recommended.
Sampling end The sample introduction interval, in minutes.
The flow rate is calculated from the pressure setpoint that is
active at the start of sample introduction.
Set the sampling end setpoint 0.2 minutes longer than the time
the sampler needs to introduce the sample. For example, the
7694 headspace sampler has an Inject time parameter which
controls how long the valve remains in the inject position. If
Inject time is 1 minute, the sampling end setpoint should be set
to 1.2 minutes. If you’re using an 7695 Purge and Trap
Concentrator, set Sampling end 0.2 minutes longer than the
Desorb time parameter.
If your column is defined and you specify a flow or pressure
program for your column, the ramp does not begin until after
the sampling end setpoint expires.
Pressure Actual and setpoint interface pressure in psi, bar, or
kPa.
Purge time The time, after the beginning of the run, when
purging resumes. Purge time must be greater than Sampl’g end.
Purge flow The flow, in mL/min, from the split vent at Purge
time. You will not be able to access or specify this value if your
column is not defined.
Interface purge time 0 to 999.9 minutes
Gas saver time 0 to 999.9 minutes Must be after purge time
Gas saver flow 15 to 100 mL/min 15 mL/min greater than
maximum column flow
Table 57 Suggested starting values (continued)
Parameter Allowed setpoint range Suggested starting
value