Is temperature ramp too big harmful to the column?

[zimanli]

We just have a Agilent 6890/5975.

I guess I used splitless injection and valve closed for a while, my system is pretty dirty. The installer genergated a method to clean the system with 40 C/min, from 200 C to 280 C, and 400:1 split, 400ml/min split. Can I run this clean method often? my column can stand 325 C.

What is the proper purge flow and time for splitless injection?

Thanks a lot!

[Earl]

Go to restek.com and look up info on split/splitless injections. This teach you some about what split flows/head pressures are generally used for different column length and diameter.
Generally you want split times to be 0.5 to 1 minute for splitless applications, but this will need to be optimized depending on what you are doing.
If the column can go up to 325, then you may want to "clean" at this temp.
if things are really dirty. I usually leave mine at normal operating flows and kick it up to max temp for about an hour or two depending on how dirty my column might be.

That's not a bad way to clean the column that the installer showed you, and the high split flow is probably to drive stuff out of the injection port.

Definitely spend some time on restek's web site as well as agilent to educate yourself about columns and the GC. Restek also offers training classes that would be benefitial to you.

to directly answer your question, it depends on what you want to do with the GC/MS.

[KC]

I would change the septum and the liner, probably clip the inlet end of the column 3-6". Then after putting it all back togeather set inj temp about 40-60 C higher than your method (but not above detector temp) and cook the column overnight at about 310 if your max temp is 325. Wait for somebody else to confirm what I have said cause I don't want to be held responsible but truthfully, thats what I would do. May even shoot a bunch of solvent blanks like acetone but not sure if that would help much if you have changed septum and liner. As far as that split ratio and flow I am not sure, sounds a little high but am not use to running much other than splittless. 40C ramp in temp gradient should not be a problem, have used it in methods many times (would use more at times if software would allow).

[Peter Apps]

It sounds from the 400:1 split that the installer thinks that you can bake the inlet clean. This is bad practise, it is much better to change the liner and septum.

Before you bake the system to "clean' it you need to know what the dirt is. If it is column bleed then trying to bake it out will only make things worse - check out earlier posts on column bleed. If it is heavy muck from samples it will usually take a hell of a lot of baking to get them all the way through the column - and then they land up in the MS, so a better approach is to clean up your samples if you can.

In any case you need to disonnect the column from the MS before you bake it out.

Peter