AAA Triptopahn preservation.

[oscarBAL]

Hello All.
I am trying to develop an aminoacid analysis in a chees factory by HPLC usig Precolum derivatation; they want need to quantify the aminoacid recory in the serum, but are specially interested in Triptophan determinacion; the regular procedure that I hav done before do not prevet this oxidation; but i found an hidrolysis procedure with tioglycolic acid; my problem is that this use Trifluoroacetic Acid (TFA). the funny thing is to bring this reagent to Costa Rica (Central America) do not care if are 5 or 200 gr; shipping this could cost $400USD and two monts... so I wonder if I can chance TFA for TCA or other acid?

Hydrolysis Solution—A solution containing 7 M hydrochloric acid, 10%
of trifluoroacetic acid, 20% of thioglycolic acid, and 1% of phenol.

sorry if I abuse of the generosity of this forum; but could someone give me a thermodinamic explaination for the use of TFA beyond a pKa reason?

Thanks in advance and best regards.

[Uwe Neue]

If you need to copy a literature method, TCA is not a substitute for TFA. However, it could work in a similar fashion. TFA has two functions. One is to provide a low pH, the other is to do some ion-pairing. I do not recall any comparisons between TFA and TCA with respect to ion-pairing capability. My admittedly wild guess is that TCA will do something similar to TFA.

[Kostas Petritis]

According to Tsugita and Scheffler 1982 Eur. J. Biochem. 124, 585-588 TFA is used in addition to HCl in order to accelerate protein digestion time and it also helps with the cleavage of hydrophobic peptide bonds. I would expect that any strong acid with side chains of equal or higher hydrophobicity than TFA to do a similar job. Just try it, you have nothing to loose (other than a day of work)...

[oscarBAL]

Thanks Alot for your comments; are very useful for me and besides now I know that TFA decrease activation energy so acelerate the digestion; and this is due a "ion pair formation" (Activation Complex) ...
Well, now I going to see if some one here have TCA.

Thanks Again.