Multiple Injections With The Mmi - Agilent Technologies 7890 Series Advanced Operation Manual

3
Inlets

Multiple injections with the MMI

82
• The vent time is too long. The inlet started to heat
while the vent was open.
If the response of early eluters is too low:
• The inlet temperature is too high.
• The Vent Flow is too high.
If the response of late eluters is too low:
• The purge time is too short.
• The final inlet temperature is too low.
If you need more injection volume and the 5 uL worked
10
to give 5X response, change the syringe to a larger one,
for example 50 uL.
Set up the data system to perform a 25 uL injection.
11
Configure the syringe. Make sure the plunger speeds on
12
the injector are still set properly.
13 Recheck the injector timings. See
14 Set a new vent time and initial inlet temperature time
based on the new time the needle spends in the syringe.
Make a 25 uL injection of your standard. Again, you
15
should see 5 times the response. If not, see
16 If you need more response, repeat steps 10 – 15 to
increase to larger volume. Also try performing 5 x 5 uL
injections, then 5 x 50 uL injections.
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.
step 12.
step 13.
Advanced Operation Manual