Chromatography Forum

Hi all,

I am working on a project that requires the use of a GC-MS coupled to a thermodesorption (TD) unit. The TD unit was attached to the GC last week, but the HP5-MS column that was previously installed wasn't stored correctly as it wasn't capped at either end. Instead of buying a new HP5-MS column I have managed to locate a brand new HP5 column in my lab, which I am hoping I can install into the GC-MS. I guess my big questions are:

1. Can you install a HP5 column into a GC-MS?
2. How does a HP5 column differ from a HP5_MS?

Thank you and best wishes,

Joe

1. Yes.
2. Lower bleed.

Unless the HP-5 MS column was heated while its ends were open it might still be in good order - give it a try.

Peter

Hi Peter,

Thank you very much for your quick response.

I had actually already installed the HP5-MS column earlier this week and after conditioning at 325C overnight I was getting a lot of bleed and my baseline was around 1 million units and drifting up as the run progressed. So I assume it's too badly damaged.

Best wishes,

Joe

Hi Joe

Make sure that you have an oxygen and moisture scrubber on your helium supply, and that it is not exhausted - contamination of carrier gas with either of these two is the main cause of column bleed.

Peter

Hi Peter,

Thanks again for such a prompt response to my questions.

With regards to your last post, I do have a non-exhausted oxygen and moisture scrubber attached to the carrier gas line. I have also run an MS tune this morning which indicates that oxygen is around 1.2 %, so I'm not sure that is my issue.

Best wishes,

Joe

Sounds like you are good to go.

Please let us know how the non-MS column performs.

Peter

1. I was under the impression - and could be wrong - that the HP-5 columns that tested out with bleed levels meeting the lowest specifications were labeled HP-5MS.

2. Wow - and maybe because we often worked at levels higher than limit of sensitivity - we never had issues with columns at room temperature sitting in a drawer, and that was not limited to HP-5, HP-1, even included 2330 and PEG columns. It would be if oxygen got to the polar columns at higher temperatures that we would notice degradation. We always got good column lifetimes too, didn't change them out on a "calendar schedule".

Hi

With regards to capping columns in storage - I was told that it was to prevent oxygen entering and damaging the phase

However, (and I may be wrong) I think that that this was wrong advice. It is my belief and experience that oxygen from air will do no harm to the column at room temperature. The only thing that capping will do is to prevent other atmospheric volatiles diffusing into the stationary phase. I never capped columns and never had a problem with any phases.

As long as the reconnected column is flushed with inert gas at a low temperature there will be no problems with oxygen interaction. The first run will clear out any ab/adsorbed volatiles.

Regards

Ralph

Hi all,

Just a quick update: I decided to take the plunge and buy a new HP5-MS column. Having installed it I am getting far better results.

Thanks for your help!

Best wishes,

Joe