Introduction to Headspace and to the 7694 Headspace Sampler
Principles of Operation
16
vial. The pressurization valve opens, allowing gas to enter the vial for the
pressurization time. The valve then closes again.
Figure 5. Vial pressurization. S1 is closed (vial raised on needle).
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) will equilibrate the loop pressure to atmospheric pressure.
Carrier
gas flow
Auxiliary gas
flow for vial
pressurization
Mass flow
controller
Pressure
regulator
Pressure
transducer
Pressure
transducer
Vent
S1
S2
1
2
3
4
5
6
Flow
restrictor
Sample
loop
To GC
Headspace
vial
Needle
Open
Closed
Carrier gas
Auxiliary gas
To Next Page
Loading...
Need help?
General
