TFA persistence

[andy_s]

Hello,

I've heard that TFA in an MS can be problematic. Looking around, I've found a lot of info on TFA's ionisation suppression, and that is not ideal, however that isn't my concern. Instead, I'm worried about longer-term problems: if I ruin my data/waste my time, I can live with it, but if I break my group's MSs, that's rather more costly! So, does anyone have any concept of any damage done by TFA, its persistence in an MS, an any other implications of using TFA for LCMS?? Asking around where I work, I'm getting mixed messages, and nothing very helpful.

Cheers,

Andy


ps. we'd be using fairly standard C18 LC, and either a Bruker maXis or Waters Synapt G2 instrument (i.e. high res. sensitive instruments that I really don't want to screw up), if that is relevant

[Bigbear]

We have 2 instruments and only use TFA on one. Another way to deal with it is to have multiple columns, to use with and without TFA.

[andy_s]

So, does that mean you DO get after-effects? Any idea how long it takes to wash the TFA out?

Andy

[mckrause]

You definitely get aftereffects and it is hard to get it out of your source. Do you have to use it?

[andy_s]

Have to is a flexible term, but I haven't got the separation anywhere near as good with anything else.

I'm trying to find out how bad it is, and how long it takes to recover. I was speaking to a colleague from another university who says that if they use it on the Friday, and leave the MS flushing over the weekend that is almost back to normal by Monday. I was suprised, but it made me wonder how long it would take us to really get back to normal... Th eonly other colleagues I know who use it say it is fine, but they are a peptide group who never do anything else.... My particular concern is that my lab spends a lot of time in negative mode, and I believe it may be more problematic there. I was hoping to canvass some experience.

[bunnahabhain]

Is it only one specific method you need TFA for? Then post some details here, I am sure we will find a way how to get around using something else. Try a different column (C18 is not C18) and see what happens with your resolution.
If you need it for more than one method, there will be a point reached soon when a second instrument will be more economic than adapting methods.

[Gaetan Glauser]

"I was speaking to a colleague from another university who says that if they use it on the Friday, and leave the MS flushing over the weekend that is almost back to normal by Monday."

Flushing for a long time is usually quite efficient but it uses a lot of solvent. Also what is back to normal? In terms of sensitivity? noise? what about negative mode?


"I was suprised, but it made me wonder how long it would take us to really get back to normal... Th eonly other colleagues I know who use it say it is fine, but they are a peptide group who never do anything else.... My particular concern is that my lab spends a lot of time in negative mode, and I believe it may be more problematic there. I was hoping to canvass some experience."

You pointed out the right thing: if you do only one application in positive mode, TFA is fine, but it ruins sensitivity in negative mode because of strong ion suppression. I never dared using TFA myself, but some colleagues reported issues during weeks in negative mode after TFA. My recommendation would be to avoid TFA on any instrument which has several users and applications, only use it on dedicated machines.

"I haven't got the separation anywhere near as good with anything else"
Tell us maybe what you are looking at and some might have alternative. In some cases, CSH phases (Waters) with formic acid can be an interesting alternative to TFA with conventional C18 material.

[andy_s]

So... from what I can tell using TFA is ill-advised unless you're (a) using only that and can sacrifice the instrument long-ish term, or (b) really desperate and have tried a lot of other things. We're neither, and use negative mode most of the time on both our instruments, so I don't want the headache. I'll persuade the collaborators to run things themselves, or do the legwork to work out an MS-friendly method.

Thank you one and all - very helpful advice. I had a feeling that we shouldn't use TFA, but wanted to check that it wasn't inherited prejudice/superstition.