120 Advanced Operation Manual
3 Inlets
14
Set a new vent time and initial inlet temperature time
based on the new time the needle spends in the syringe.
15 Make a 25 uL injection of your standard. Again, you
should see 5 times the response. If not, see step 13.
16 If you need more response, repeat steps 10 through 15 to
increase to larger volume. See the next section. Try
performing 5 x 5 uL injections, then 5 x 50 uL injections.
Multiple injections with the PTV inlet
The preferred technique for concentrating analytes in the
inlet liner is to use a single, large volume injection. Using a
high capacity syringe and one septum puncture reduces the
possibility of contamination and generally improves results
when compared against a multiple septum puncture
technique. However, if needed, you can perform multiple
septum punctures during the vent time. This technique
requires an Agilent data system and automatic liquid
sampler.
Data system requirements
An Agilent data system is necessary for multiple injection
because the needed parameters are not available through the
GC keyboard.
GC ChemStation Software revision B.04.01 SP1 or later.
MSD ChemStation Software revision E.02.00 SP2 or later
EZChrom Software revision 3.3.2 or later
Setting parameters for the inlet in solvent vent mode
Set or configure the following parameters in the data
system's 7890A GC method editor.
Syringe size — Verify the syringe size is configured correctly.
The configured syringe size changes the available choices for
injection volume.
Injection volume — Select the injection volume, then enter a
number of injections. The total injection volume will be
displayed.
Multiple Injection Delay — A pause time, in seconds,
between injections. This is added to the minimum hardware
cycle time.
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