Peak leading

Chromatography Forum: GC Archives: Peak leading
Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Thursday, December 19, 2002 - 06:13 am:

Hi,
I am runing acetylated compounds in a BP-1 column but the peaks are leading very much (USP tailing factor is 0.62)I know that thi first thing I should try is decrease the sample size injected or increase the split ratio, but even with a very small peak because of the great split ratio it still leads,only overloaded column give peak leading?the column works well with any other compound.

Regards


Top of pagePrevious messageNext messageBottom of pageLink to this message  By rodney on Thursday, December 19, 2002 - 06:41 am:

Dear Anon,

You have a good understanding of what is happening. The peak must be very polar.

To improve the peak shape use a slightly more polar column.

A 5% Phenyl or a OV-1301(SPB-624) might be a great improvement and keep separations similar to the BP-1 you are using now.

As you see, when you put a very polar compound on a non-polar phase you get the asymmetrical peak shape.

Rodney George
Senior Research and Development Chemist
Gas Separations Research
Supelco
595 North Harrison Road
Bellefonte, PA 16823

814-359-5737 voice
814-359-5702 fax
rgeorge@sial.com


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Anonymous on Thursday, December 19, 2002 - 11:52 am:

thanks Rodney,

only one more doubt,I have acetic anhydride in my injection solution.let's suppose that I use a phase like the BP-10 or a carbowax column(BP-20) ,these are much more polar than a 5% phenyl phase,can the anhydride damage these columns?

Regards


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Rodney on Thursday, December 19, 2002 - 03:33 pm:

Dear Anon,

Although there a terminal hydroxy on the polymer of the Carbowax 20M phase, any esterification that might occur is reversible. No permanent damage is done. It is the esterification of that hydroxyl which makes the phase become chemically like the FFAP or Nukol phase.

Carbowax 20M is commonly used to analyze acetylated mono-alcohols. If you are doing sugar alcohols, a derivatized amine, or a higher molecular weight compound, I would suggest you do not use this phase unless you understand its limitations.

If you would email me directly with additional information I would be glad to advise you privately. There are possible problems if I am guessing correctly what you are doing.

Rodney George


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