Chromatography Forum

I was wondering if I contaminated my column when I attempted to clean the glass insert on my chromatograph. I removed the glass insert with tweezers and had gloves on while I was handling it. I rinsed the insert with acetone and let it dry before reinstalling. Since then I noticed there is a large hump in the 10 to 15 min range. If I leave the chromatograph running over night and make a run in the morning I get a chromatogram without this hump, as shown in the following picture:



Any subsequent runs yield a chromatogram with a hump in the 10-15 minute area, as shown in the following picture:



Since then I removed the glass liner I attempted to clean and replaced with a brand new one. I was careful to keep it clean during handling(disposable gloves, used tweezers when able to) and I even replaced the septum at the same time. However, I am still getting this peak on subsequent runs after the first run after the chromatograph has been running overnight.

From what I have read I think I may have contaminated part of the column with something that doesn't elute on the first run but, when the column is heated up, vaporizes and shows up in all subsequent runs. Any ideas on what may have happened or ways to remedy this, such as cutting a small section off of the beginning of the column to eliminate this contaminated section?

I am using the following:
GC: Shimadzu GC2010 plus
column: Restek Rtx-200 Crossbond trifluoropropylmethyl polysiloxane 30 meter, 0.53 mmID, 0.5 µm df
UHP Helium carrier gas
I've ever only used SPME fiber for analyzing BTEX in this column and injector

Thanks

Do a blank run (no sample) and a run with solvent using the same method.

If the hump is present in the blank run = column contamination
-> do a 1-2 hour column baking
If the hump is in not the blank run = inlet contamination
-> the solvent run should confirm this
-> if you also increase the inlet temp in the bake out method it could go away, if it is still there after baking a thorough cleaning of the inlet is necessary (follow producers guidelines).

Hello

1.Cut 0.5m of column from both sides
2.Run method with no injection - only temperature gradient:
- if you still see it it is probably column (bake it out in 10 deg lower than maximum temp for column for few hours)


Regards

Tomasz Kubowicz

Thanks peturari and Tomasz Kubowicz (tkubowicz)! I'll try those suggestions probably in the next week or two and let you know how it worked out.

Best regards,

-Dustin