M
AINTENANCE
General GC Maintenance
CP-3800 GC Getting Started Manual
49
The use of soap-based leak detection fluids is not recommended for a high
performance capillary Gas Chromatograph due to the danger of introducing
contaminants into the system. If leak detection fluids are being used they
should only be used outside the Gas Chromatograph, i.e., to verify there are
no leaks in the plumbing to the Gas Chromatograph. If a leak detection fluid
is being used inside the Gas Chromatograph, an alcohol such as isopropanol
or a 50:50 mixture of isopropanol and water should be used. Use a dropper
or syringe to place a few drops of leak detection fluid on the desired fitting
and monitor the area for bubble formation.
The most important step in leak checking is to verify that the GC system can
hold pressure. This is done by removing the column from the injector, sealing
all exits from the injector and pressurizing the system. Use the following
procedure to leak check 3800 injectors:
Note: When conducting leak check procedures it is important to completely
seal all carrier gas exits, including septum purge and split vent outlets. If
more than one injector is present, then the outlets of all the injectors must be
sealed. The following procedure refers to one injector but should be
duplicated for every injector on the 3800.
1
Set the column oven and the injector zone temperatures to 50°C
and allow them reach this temperature. This allows safe handling of
injector surfaces.
2
Remove injector septum nut and install a new septum. An older
septum can often be the source of a substantial leak.
3
Remove the column from the injector. Use the appropriate nut and
ferrules to seal the base of the injector. For packed column
systems use a 1/4
″
Swagelok blank off plug (P/N 16-000154-00).
For capillary systems use a capillary nut (P/N 03-949551-00) with a
no hole ferrule (P/N 28-694590-01).
4
If the injector is a 1079, then the septum purge and split vent
outlets must be sealed. The septum purge outlets are located on
the top frame surrounding the column oven, behind the column
oven door. The split vent outlets are located on the left side panel
of the 3800. Seal the septum purge by removing the outlet fitting
from the septum purge valve and replacing it with a blank off plug
(P/N 16-000154-00). Seal the split vent outlet by installing a
Swagelok union on the outlet tube and sealing it with a blank off
plug.
