Introduction to Headspace and to the 7694 Headspace Sampler
Modes of Operation
20
maintain the same incubation interval during the gas chromatographic run,
vials are transferred one by one into the oven and recovered after sampling.
The sampler analyzes the event times and the GC cycle time, then adjusts vial
delivery and recovery times to optimize overall process time. Vial agitation is
allowed in this mode.
Note that the GC run cycle time is the time from injection until the system is
READY for another injection. Occasionally, the time for data handling will
become a factor.
The diagram above shows how the instrument actually synchronizes the
availability of a vial which has been heated and is ready for injection, with the
GC’s readiness for another injection. For simplicity, the two cases are:
Situation A: total preparation time of 30 minutes, with run cycle time of
15 minutes.
Situation B: total preparation time of 15 minutes, with run cycle time of
30 minutes.
Sequence of events–G1883
The normal sequence of events is:
Run 2 Run 3
Vial 1 prepared Vial 2 prepared Vial 3 prepared Vial 4 prepared
Minutes
15 30 60 90 130
Run 1
A
B
Run 2 Run 3Run 1
Vial 1 Vial 2 Vial 3 Vial 4
prepared prepared prepared prepared
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