Clarus 600/680 User’s Guide
3-41
Set up the Splitless Mode for a CAP or PSS Injector
The Splitless Mode is used for trace analyses. Most of the sample is transferred onto the
column, then the split vent is opened, thereby venting any sample remaining in the
injector liner. This step describes how to set the split mode for PPC modules. .
NOTE: In the Splitless Mode, the split vent must be opened after the sample has transferred to
the head of the column (i.e., 0.5 - 2.0 minutes after the run has started).
The procedure which follows assumes that the carrier gas pressure has been set (see Step
C in this chapter).
NOTE: The injector is shipped with a wide-bore injector liner. You may want to install a narrow-
bore liner. Both liners must be packed with quartz wool before running your analysis.
Refer to Step B, Connect the Column to the Injector in this chapter, for procedural
details.
Splitless Injection with Pressure Pulse (Flow Pulse, Velocity Pulse)
Technique
Pressure (flow or velocity) pulse injection is recommended for splitless operation,
especially when analyzing wide boiling-point mixtures and/or large volume injections.
This technique increases the pressure (flow, velocity) in the system at the time of
injection to minimize the gas expansion in the injector liner and maximize the gas sample
transfer onto the column. Therefore, you should use the highest pressure that your
application will allow. This provides better peak shapes, better recovery, and no
discrimination for both low boiling and high boiling compounds.
This technique can be incorporated in your GC method. The initial pressure (flow,
velocity) is high (for example, 70 psig) and held at this high pressure for enough time (for
example, 0.25 to 2.0 min) to transfer your sample onto the column. This time needs to be
experimentally determined for your sample, injector temperature, and injector liner used.
You want a time that will allow most of your sample to transfer onto the column as well
as maintain good solvent and analyte peak shape. If the time is too short, you will lose
sample; if the time is too long, the solvent will tail and possibly obscure or affect peak
shape of early analytes. The split vent is off at injection (Split Flow = zero).
The pressure (flow, velocity) is then programmed at a controlled rate, down to the normal
column operating pressure (flow, velocity). At the same time, the split vent is set back to
normal flow to clean out any remaining sample in the liner and to release the pressure in
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