By Anonymous on Sunday, June 15, 2003 - 08:23 am:
i have prepared TEAA by add TEA into mobile phase first then adding acetic acid to desired pH.
the problem is after preparative run when i rotovap down the solvent there is a yellowish viscous liquid in the flask and it is very hard to dry it out.
my sample is amino acid derivative and in solid form before prep, low solubility in most solvents, with a drop of TFA in methanol it dissolve much better. the prep mp is TEAA/MEOH, but 90% is aqeuous, so i would expect it to precipitatae out fastly when rotovaping, and TEAA also volatile so will be gone, not the viscous liquid.
so anyone know is it because the TEAA may not being volatile. a small portion of dried collections shows the TEAA salt is still there by analysis.
anyway, is there anything to know for removing TEAA after separation?
thanks?
By Anonymous on Monday, June 16, 2003 - 07:00 am:
Some possibilities?
Have you methylated your amino acid, are you recovering the same material you started with?
When you rotavap, keep coevaporating with methanol to dry everything down. Do this at least three times.
Are you certain of the quality of your tea?
By Anonymous on Monday, June 16, 2003 - 08:24 am:
>Have you methylated your amino acid, are you >recovering the same material you started with?
NMR shows the starting compound is there, however, if methylation happened during the rotovap step, i do not know. probably not, since i also have portions dry down without rotovap, and the liquid still there.
>When you rotavap, keep coevaporating with >methanol to dry everything down. Do this at >least three times.
what's the point to do it three times?
>Are you certain of the quality of your tea?
yes, the TEA is good.
By Anonymous on Monday, June 16, 2003 - 02:03 pm:
I'm sorry, there was no particular scientific reason to coevaporate 'three' times with methanol.
It's just that everyone in the group that I work in coevaporates their TEAA/MeCN HPLC fractions several times with some alcohol and this gives dry enough fractions to dissolve in some sort of buffer and pass on to biologists to use in assays.
I always see the issue of a viscous liquid that you talk of, although not the coloration, and coevaporation sorts it out.