By Bob F. on Friday, July 9, 1999 - 03:22 am:
I am currently analysing aromatic sulphonyl chlorides by HPLC. The method contains 0.1% Trifluoroacetic acid in the mobile phase but what is the purpose of the TFA? presumably it is more than just to acidify the eluent - what is the advantage over acetic acid if it is to block active sites on the column?
By Tom Jupille on Friday, July 9, 1999 - 09:26 am:
pKa of acetic acid = 4.75
pKa of trifluoroacetic acid = 0.3
By Chris Pohl on Friday, July 9, 1999 - 01:26 pm:
Generally,TFA is added as a "ion pair" reagent in HPLC systems. Because this ion is considerably more hydrophobic than acetate, it works much better in this regard although it is a relatively wimpy ion pair reagent when compared with more conventional ion pair reagents. However, since the analytes you mentioned are not ionic the only possible function of the TFA in your system that I can think of would be in regard to the ability of TFA to suppress the hydrolysis of the sulfonyl chloride analytes. In this regard, TFA being a much stronger acid would function much better than acetic acid.
By Michael Breslav on Thursday, July 15, 1999 - 09:26 am:
Also, because you need less TFA than acetic acid to get the same effect, the mobile phase is more transparent at 210 nm UV.
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