Hi,

What is the column description, are you saying the spectral line(m/z) or peak in the TIC (RT (min)) . if you are saying about TIC peak; please change the liner, septa and heat the column to 10 deg less than Max Temperature of column for 2 hours with 1.0 mL/min and inject a solvent alone to verify the column.

Regards

Selvan

It could be ionization box or quadrupoles are contaminated.

Please remember that you do not inject so much sample into the GCMS, as you do for GC.

Dear Thanawat,

Yes it sounds like a system contamination!

Try cleaning out the liner and purging the injection port at high temperature (into a short length of capillary) into the air.

Use a freshly cleaned liner and new septa.

I have described a method for cleaning injection ports in another entry. (Laura derivatised sugars/algae).

Prime a new capillary column by programming up to the max several times into the air.

Reconnect to MS.

As Temel says, be careful what you inject!

Always clean up a sample before analysis if you wish to analyse extracts at uber high sensitivity!

Hope this helps!

Regards,

Dr John

i agree with john i.e to clean the colmn.In first step you make some injection with only solvent and make a blank run.In secon phase if the problem persists go the method that call baking method.it will be more helpful.

I agree with Rehan, also if desperate an injection of a not too strong solution of a non corrosive silylating agent (eg BSA in toluene say) (with column disconnected from the MS and bleeding into the oven) can sometimes derivatise what has become trapped and help purge it from the column! Last resort though!

Thanks john