Varian 450-GC, User Manual

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Maintenance
Page: 432 User Manual 450-GC Varian, Inc.
Injector Maintenance
The Injector is the component of the Gas Chromatograph that requires the most
frequent maintenance. This is due to the fact that the sample is deposited in the
Injector, thus leading to potential contamination and build up of non volatile
deposits. The most frequent Injector maintenance is septum replacement. In
addition insert replacement and Injector cleaning are very common. As septum
replacement is common to all liquid Injectors on the 450-GC this procedure is
presented first, followed by instructions for High-Temperature bake out of the
Injector, followed by specific maintenance procedures for the individual
Injectors.
Septum Replacement
The Injector septum is an expendable part and must be replaced on a routine
basis. The frequency of replacement depends on the number of injections and
whether the injections are by hand or with an autosampler. In general the
septum should be replaced every 50 - 100 injections or when symptoms of a
septum leak are seen. These symptoms include changing retention times,
reduced detector response or a drop in column head pressure. The latter
symptom is not always valid as some Injectors, such as the 1079 PTV, are
pressure controlled. With a pressure controlled Injector, the column head
pressure will remain constant even if a leak is present.
Use the following procedure to change a septum on any Varian Injector:
1. Cool the column oven and Injector oven to 50°C. This ensures safe
handling of Injector parts and protects the column from elevated
temperatures while it is exposed to air.
2. Turn off the carrier gas supply to the Injector to prevent the septum from
being inadvertently ejected due to carrier gas pressure.
3. Remove the Injector nut by turning it counterclockwise.
4. Remove the old septum using metal tweezers or a septum pick (P/N 72-
000084-00). Do not to handle any internal parts of the Injector with hands or
gloves.
5. Install the new septum, again using tweezers to avoid contaminating the
Injector.