38 User Information
Introduction to Headspace and to the G1888 Network Headspace Sampler
Filling the sample loop
The vent valve opens and the headspace gas fills the sample
loop. It then vents to atmospheric pressure through the vent
outlet. A short loop–fill time (2 to 5 seconds) may leave
pressure in the loop equilibrated to the vial pressure and allow
more analyte to be injected. A longer loop–fill time
(10 to 15 seconds) equilibrates the loop pressure to atmospheric
pressure. See Figure 9.
Figure 9 Loop fill. S1 is closed. S2 is open to fill the loop.
Carrier gas flow
Mass
controller
Pressure
transducer
Vent
Sample
loop
To GC
Auxiliary gas flow
for vial pressurization
Pressure
regulator
Pressure
transducer
Flow restrictor
S1
S2
Needle
Headspace vial
Open
Closed
Carrier gas
Auxiliary gas
1
2
3
4
5
6
flow
Toggle
switch
Toggle
switch
medium_standard.book Page 38 Tuesday, February 17, 2004 10:14 AM
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