Extraction Mode - Agilent Technologies 7697A Advanced Operation Manual

3
Method Development

Extraction mode

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• If set to 0, the HS will control the sample loop fill until
the sample loop (and vial) pressure reaches 1 psi (about
6.9 kPa). Then then vent valve will open completely. The
HS does not control the sampling system at this point.
When the pressure reaches 0 relative to atmospheric, the
vent valve closes. Using this setting may not provide
repeatable results.
• If set to a value between 0 and 1 psi (6.89 kPa), a
warning appears. The HS will attempt to control the
venting to this value, but there may be a loss in
repeatability or sample.
Loop equilibration: Set a time for the sample loop to stabilize
after filling.
Possible issues
• If using a small sample loop, and peaks areas are small,
you may be oversweeping the loop. If the difference
between the initial and final vial pressures is too great
given the sample conditions and loop size, too much
sample may be flowing through the loop to vent. Try
reducing the vial pressure or lowering the difference
between the initial and final pressures (which reduces the
amount of time the headspace volume sweeps the sample
loop).
• If using a large sample loop, and peak areas are small,
you may not be sweeping enough sample into the loop.
Try increasing the vial pressure or setting a lower loop
final pressure (which increases the length of time the
headspace volume sweeps into the sample loop).
Set the extraction mode by pressing the [Adv Function] key.
There are 3 modes available, Single, Multiple, and Concentrated.
See "Types of HS Extractions and Injections"
descriptions of HS behavior for each mode.
Single extraction
In this mode, the HS equilibrates the vial, punctures it once,
fills the sample loop (one "extraction"), then starts a run
while injecting the sample onto the GC.
If a vial appears more than once in a sequence, it is
completely reprocessed (whether in standalone mode, or if
using an Agilent data system).
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Advanced Operation