UV detection limit for TFA

[ande2922]

Hi everybody.
I've been trying to run a mobile phase of A= 0.1% TFA/H20, B=0.1% TFA/MeCN for a few days, but I've been getting really nasty looking blanks. I changed the column, made fresh buffers and flushed out the system, so I'm pretty sure the problem is with the TFA that I'm using (Fisher 98.5%). Is there something in there that would absorb strongly at 218nm, or am I just using a type of TFA that is unfit for HPLC?
Thanks,
Chris

[Chris Pohl]

Chris,

There is definitely a big difference in quality of TFA from various sources (and TFA doesn't seem to age well). The best approach is to get the grade for RP HPLC from Aldrich or Pierce that is in ampules and use them as you need them.

[marc]

Hi Chris,

Dr. Pohl reiterates something I read on ABRF posts a lot. TFA doesn't keep and quality depends on the source. I keep mine in brown bottles and throw them away after a week. Another trick is to use a little less in your ACN side (depending on what wavelenth you are monitoring). The acid/conjugate base have different spectra and the dissociation constant is quite different in organic vs water. You can play around with it but I think I use about .1% in water and 0.075% in ACN to get a pretty flat gradient blank at 218 nm.