Chromatography Forum

Hi All,

I have a very naive question. After 4 years of use - 18 500 injections, my GCMS column start to bleed a bit too much to my liking. I get these pesky m/z 207 and 281 ions.

I guess it's time to change it (trimming the injector bits didn't help...Or should I trim also the MS side?)

I am thinking about buying a new column. So far I have a L × I.D. 30 m × 0.25 mm, df 0.25 μm - poly(5% diphenyl/95% dimethyl siloxane) phase (supelco Equity-5 Capillary GC Column).

So any idea how to stop the bleeding?

A. Trim the end side of the column that goes into the MS? how many cm?

B. Buy a new column? if yes, which one do you recommend for general small organic molecules (mass from 150 to 400 max)?

Thanks a lot!

After 4 years of use - 18 500 injections, my GCMS column start to bleed a bit too much to my liking.

Time for a new column - and a spare column.

Get your pointy-haired boss to open up his wallet.

In the consumer products business, we used primarily non-polar capillaries like DB-1 and DB-5.

We've used Restek RTX-5Sil MS 30m/0.25mm/0.25um with good performance. Recently we've switched to Phenomenex ZB-Semivolatiles column with even better performance. It's my go-to for a "5-type" column in our lab. Ultra low bleed, great separation on critical pairs, and competetive column lifetime.