Chromatography Forum

hellow every one .
i have thermo trace 1300 gc linked by isq 7000.my problem about nitrogen leak and high background in chromatography.i tried to detect the problem .from test the manifold on the gas cylinder to tighten the ferule of gc and ms transfer line .
.that is right .and how i make tight the ferule .and what about other position can make leak ..

An air "leak" will usually show as a roughly 7:3 nitrogen:oxygen ratio.

If you're seeing a lot more nitrogen than oxygen(well beyond this ratio) look at places other than a vacuum leak.

Have your recently changed your carrier gas filter? They usually come purged from the factory with nitrogen, and the normal procedure is to use a high carrier gas flow and really, really high split ratio(something like 400:1, check the instruction with the filter and your instrument) for a while to purge out the N2.

The other possibility-don't rule out a contaminated He cylinder. As He supplies have shrunk, getting higher than normal N2(even in a "5 9s" cylinder) isn't unheard of.

An air "leak" will usually show as a roughly 7:3 nitrogen:oxygen ratio.

If you're seeing a lot more nitrogen than oxygen(well beyond this ratio) look at places other than a vacuum leak.

Have your recently changed your carrier gas filter? They usually come purged from the factory with nitrogen, and the normal procedure is to use a high carrier gas flow and really, really high split ratio(something like 400:1, check the instruction with the filter and your instrument) for a while to purge out the N2.

The other possibility-don't rule out a contaminated He cylinder. As He supplies have shrunk, getting higher than normal N2(even in a "5 9s" cylinder) isn't unheard of.

many thanks ms benhutcherson for response
but what about (really high split ratio(something like 400:1, )
i think these split ratio will affect on result's .that is very very small percent of injected volume will inter thr column and may unknown cant be detected ,,
can you explain your words please ,
many thanks

The 400:1 split ratio is only for a few minutes to get nitrogen flushed out of a new carrier gas filter. Once the filter is filled with helium, you can safely resume your normal program(including column flow and split ratio).

The 400:1 split ratio is only for a few minutes to get nitrogen flushed out of a new carrier gas filter. Once the filter is filled with helium, you can safely resume your normal program(including column flow and split ratio).

THANKS A LOT
MANY THANKS