Chromatography Forum

Time is off the essence here... I need to to get things running ASAP !!!!

I went to condition a new column (100m non-polar) at 300C on a new system. What I did not realize is that the engineer who installed it only set the the input He Pressure to about 78PSI... so the inlet shut down. I found it with no flow...

Does that mean flow stopped when it was about 300C so air probably got in and so wrecked the column?

(I did this twice before I realized what was happening)

I'm in the process of actually conditioning that column now... Should I even bother? Should I just go with a new column? I have one spare that as was to go on a another system later this week for another high priority project, but this system needs to be up NOW!


Thanks,
- Karen

What detector are you using?

It isn't the best thing for a column, but most today are much more rugged than they were many years ago. What is the actual phase of the column and what does the documentation say is the upper temperature limit?

What detector are you using?

It isn't the best thing for a column, but most today are much more rugged than they were many years ago. What is the actual phase of the column and what does the documentation say is the upper temperature limit?

As I was conditioning it was not hooked to any detector.


The phase is 100% dimethylpolysiloxane 0.5um upper limit 325C/350C

Resolution is critical for this method... It's a complex difficult separation.

- Karen

Hi Karen

The kind of damage that you might have done will have an impact mainly on the adsorptive activity of the column - so if your analytes do not have -OH groups and similar sticky groups you might be fine. I would be surprised if you would be putting alcohols through a 100 m non-polar column anyway - hydrocarbons or fames would be my guess.

Anyway - the proof of the pudding is in the eating - you can check resolution without reconditioning the column by injecting a test mixture or a sample - if the peaks separate the column is OK, if not - it's not. As Hans Muller used to say on here "Don't think, measure !".

If I was in a hurry I would chop 2m off the inlet end and 5m off the detector end where any damage is most likely to be localized.

Even if the column is OK now you should anticipate a shortened lifetime, but you can worry about that when the time comes.

Peter

The kind of damage that you might have done will have an impact mainly on the adsorptive activity of the column - so if your analytes do not have -OH groups and similar sticky groups you might be fine. I would be surprised if you would be putting alcohols through a 100 m non-polar column anyway - hydrocarbons or fames would be my guess.

Thanks Peter.

There can be small amounts of alcohols and other oxygenates which could cause issues... At this point I am going to try it... This will be the first time doing this analysis, so I won't have any chromatography to compare against, which makes things a bit more uncertain.

- Karen

100 m columns are generally on the expensive side. I'd do a lot of checking before I threw it away. All of the advice given above is great. Do it all and give it a workout. I'll bet it'll be ok.

Most GC's have non-self-destruct routines. When the gas pressure drops to zero, it should shut off all of the hot zones. My Agilent systems that are 6890 and newer all do that.

100 m columns are generally on the expensive side. I'd do a lot of checking before I threw it away. All of the advice given above is great. Do it all and give it a workout. I'll bet it'll be ok.

Most GC's have non-self-destruct routines. When the gas pressure drops to zero, it should shut off all of the hot zones. My Agilent systems that are 6890 and newer all do that.

Hi Karen

I went to condition a new column (100m non-polar) at 300C on a new system. What I did not realize is that the engineer who installed it only set the the input He Pressure to about 78PSI...

What is your instrument/detector and column id and linear velocity and upper temperature of your analysis? From my pressure/flow calculator there are some conditions that could have pushed you over the 78psi supply but it depends on the column id.

For an optimum linear velocity of 30cm/sec. A 320um id should not have pushed you over the limit unless you had a slight leak on the inlet

Anyway, take the advice from Peter, James and Rb6banjo and just run a sample and see if the peak shapes are OK

Regards

Ralph

Karen,

I wouldn't be too concerned about cutting off some meters on either end, as suggested earlier. I understand your concern, a 100 meter column is expensive.

My experience is that you should be able to optimize most (all?) separations with a column shorter than 100 meters. I have some experience with method optimization, and will make this proposal: send me some data about your current separation- column, conditions, peak retention times, etc.. I will optimize the separation for you using sophisticated optimization software. I'm guessing the separation can be optimized to give better resolution, in less time, on a shorter column (maybe a MUCH shorter column).

cheers,
Mark Cipollone
The 4S Company
developer of GC-SOS simulation & optimization software