User guide

Inlets 8
Advanced User Guide 183
If a column in the flow path is not defined
1 Press [Front Inlet] or [Back Inlet].
2 Set the inlet temperature.
3 Set Total flow into the inlet. It must exceed your intended
Septum Purge flow. Measure the split vent flow using a flow
meter.
4 Subtract split vent flow and septum purge flow (see “Pre
Run and Prep Run” on page 171) from Total flow to get
column flow.
5 Calculate the split ratio (split vent flow/column flow). Adjust
as needed.
Selecting parameters for the S/SL splitless mode
A successful splitless injection consists of these steps:
1 Vaporize the sample and solvent in a heated inlet.
2 Use a low flow and low oven temperature to create a
solvent- saturated zone at the head of the column.
3 Use this zone to trap and reconcentrate the sample at the
head of the column.
4 Wait until all, or at least most, of the sample has transferred
to the column. Then discard the remaining vapor in the
inlet—which is mostly solvent—by opening a purge valve. This
eliminates the long solvent tail that this vapor would
otherwise cause.
5 Raise the oven temperature to release the solvent and then
the sample from the head of the column.
Some experimentation is needed to refine the operating
conditions. Table 31 provides starting values for the critical
parameters.
Table 31 Splitless mode inlet parameters
Parameter Allowed setpoint range Suggested starting
value
Oven temperature No cryo, 24 °C to 450 °C
CO
2
cryo, –60 °C to 450 °C
N
2
cryo, –80 °C to 450 °C
10 °C below solvent
boiling point
Oven initial time 0 to 999.9 minutes ≥ Inlet purge time
Inlet purge time 0 to 999.9 minutes 2 x Liner volume
Column flow