Chromatography Forum

We determine residual methanol, tert-butylmethyl ether and tert-butanol in the sample. CP Sil 5 CB (50m x 0,53mm ID x 5mcm film thicknes) is used, Split injection and T program 50stC (10min) - 40stC/min - 200stC (10 min); solvent dimethylformamide; sample conc is 200mg/ml. Peaks of residual solvents are OK, however at the beginin of Run we can see a lot od additional peaks. It is much more christmans tree.

Does anybody have any idea what would be these peaks or what is the source of christmans tree peaks. Unfortunately I can not show chromatograms, but I can send them by mail if somebody is interested.
Thank you for answering.

Ana

Hello Juju

I'm little surprised you use in split mode 40°C/min for your temp.program.rise !!!

Is it yours first injection for this analyse or you make it for a long time ?

Maybe peak parasite are due to a contamination in injector........try to condition it , even the column (if you never do it before!) because it's a large film tichness.

Hello Juju

I'm little surprised you use in split mode 40°C/min for your temp.program.rise !!!

Is it yours first injection for this analyse or you make it for a long time ?

Maybe peak parasite are due to a contamination in injector........try to condition it , even the column (if you never do it before!) because it's a large film tichness.

Hello BG!
This method is not used at first time, but it happened at first time. These peaks appear in the chromatogram of the sample, but not in the chromatogram of the standard.
Why are you suprised?
Thanks
ana

in general in split mode rise are less important 5°C/min to 10 even a little more but rarely 40°C/min

With hight film tichness (5µm)you can have a big bleeding.......no ?

Hello BG!
I do not understand your answer quite well, but all residual solvents eluted in 10 min at 50stC and after residual solvents eluted we start program 40stC/min to force the elution of the solvent.
Column bleeding is not the right answer because this happen only in the chromatogram of the sample and not in the standard chromatogram.
Thanks
ana

No NO i'm agree with you , for me the rate was a special case with any relation with your pb........if it's working , its find!

but about your pb if it happen only with your sample, i'm always agree with we can say it isn't the system so looking for your sample; is there any change in the matrix or any degradation possible????

If the peaks don't appear in your standard but in your sample,these are relative to your matrix.

Bye