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5
Micro GC Channels
Dynamic Electronic Gas Control (DEGC)
Dynamic Electronic Gas Control (DEGC)
The Micro GCs have built-in regulators that can be adjusted to get a constant or programmed
pressure control, which, once constant or programmed pressure control is obtained, results in a
constant or programmed flow through the injector, column, and detector. The pressure range is
from 50 to 350 kPa (7 to 50 psi). This pressure sets a continuous flow of carrier gas of about
0.2 to 4.0 mL/min, depending on column length and type.
A typical pressure rise is 200 kPa/min, which will give a significant pressure increase during the
run without excessive baseline disturbance. In most cases, baseline subtraction may improve the
quality of chromatograms that suffer from baseline drift.
Inert Sample Path
The 990 Micro GC is equipped with an Ultimetal-treated sample path. This deactivation method
ensures the integrity of the sample and helps to achieve the best detection limits possible.
The deactivation is applied to tubing running from the sample inlet to the injector.
Injector
The injector has a built-in 10-µL sample loop that is filled with the gaseous sample. The pressure
of the sample should be between 0 and 100 kPa (0 to 15 psi) and the sample temperature within
0 to 110 °C.
When the chromatographic data system sends a START command, the vacuum pump draws the
gas sample through the loop. Then, after the pump stops, the injector injects the gas sample from
the sample loop into the gas stream. A typical injection time is 40 ms. This equals an average
injection volume of 1 µL. A practical minimum value is 40 ms. A value of 0 to 10 ms might result in
an injection that is not repeatable.
Agilent 990 Micro GC User Manual
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