TFA concentration

[chichibabin]

Hi All,
When doing RP-HPLC with water and acetonitrile as mobile phases I have seen in the literature people adding 0.1% TFA to the water (phase A) but only 0.08% TFA to the acetonitrile (phase B). Does anyone know the rationale for doing this?
Cheers,
Sat

[Noser222]

It gives a better baseline that way, since the absorbance of the mobile phase changes during the gradient.

[chromatographer1]

Good answer Noser222. But to explain with more detail:

Better baseline in the sense of flatter and easier to integrate later eluting peaks.

I discovered this (before I ever saw it published) in work I did in 1985, although I used 1.0% and 0.9%.

Don't know who discovered it first, but it was very helpful in integrating late eluting peaks. Of course it was shared with our peptide suppliers immediately and I saw it everywhere a few years later. I did not completely understand why at the time it worked so well. I have heard explanations of the phenomenon since but I cannot confirm them so I won't go into it.

It has never made a difference in any analysis I ever did, but of course there may be an exception.

best wishes,

Rod

[tom jupille]

There was a fairly thorough article on this in LC-GC Europe in early 2003:
http://www.lcgceurope.com/lcgceurope/da ... rticle.pdf

[adam]

Tom

Any chance you could also send links to the other articles in this series (Part II, Part III, etc).

Thanks
Adam

[tom jupille]

There were only two parts. The second deals with temperature and RI effects:
http://www.lcgceurope.com/lcgceurope/ar ... p?id=75777

[chichibabin]

Thanks Guy's. I guess I will try 0.08% TFA in my MeCN.
Cheers,
Sat

[jzt]

does anyone know if the same trick will work with methanol mobile phase? i.e., mp A is 0.1% TFA in wter, mp B is 0.08% TFA in methanol? or do we need a different percentage of TFA in methanol to achieve the same results?

[tom jupille]

does anyone know if the same trick will work with methanol mobile phase?

That specific trick is unique to the interaction between THF and ACN. That's why I posted the link to the Rozing article in LCGC Europe.