Instrumentation for Gas Chromatography - Forensic Applications of Gas Chromatography - page 11

Septum
Carrier gas
Split outlet
Liner
Column
Figure 2.7 Split/splitless injector.
syringe that has a fine needle that can be inserted into the capillary column.
On-column injection is a nonvapourising technique, as the sample reaches
the column as a liquid. A disadvantage of this type of injector is that the inter-
nal surface of the column stationary phase will be damaged by the insertion
of the syringe needle unless a retention gap is attached to the column. ( Note:
A retention gap is a short length of capillary tubing without the stationary
phase being present on its internal surface.)
2.3.3 Programmed Temperature Vapourisation Injector
A programmed temperature vapourisation (PTV) injector (Figure 2.8) is a
combined modified version of the split/splitless and on-column injectors. The
sample is introduced into a cold chamber and is then subjected to rapid heating
to affect vapourisation of the sample. The major advantage of this approach
is that the sample volume can be relatively large (up to 250 μL, compared
to 1 μL in the case of the split/splitless injector). This large volume injection