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Operation Manual 217
About the Volatiles Interface
The volatiles interface provides a simple, reliable way to introduce a gas sample into your GC
from an external device such as a headspace, purge and trap, or air toxic sampler. Manual
syringe injections cannot be made with this interface. The interface has a small volume and is
highly inert, ensuring high sensitivity and resolution for applications requiring trace level
detection.
Total flow to the interface is measured by a flow sensor and is divided into two streams. One
stream connects to the septum purge regulator; the other splits to the gas-phase sampler (and
from there is introduced into the interface) and the pressure sensing line. The pressure
sensing line is measured by a pressure sensor. This stream also provides a trickle flow to the
interface.
VI operating modes
There are three modes of operation—split, splitless, and direct. The pneumatics differ for each
operating mode and are discussed in detail in the rest of this document.
Table 31 summarizes some issues to consider when choosing an operating mode.
Specifications for the interface are also listed.
Table 31 Overview of the volatiles interface
Mode Sample
concentration
Sample to column Comments
Split High Very little, most is
vented
Splitless Low All Can switch to split mode
electronically.
Direct Low All Must physically disconnect
split vent, plug the interface,
and reconfigure the GC.
Maximizes sample
recovery and eliminates
possibility of contamination
to pneumatic system.
Table 32 Specifications of the volatiles interface
Specification Value/Comment
Deactivated flow path
Volume 32 µL
Internal dimensions 2 mm by 10 mm
Maximum flow to interface 100 mL/min
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