Chromatography Forum

Has anyone used ammonium fluoride as a mobile phase additive for LCMS work in either positive or negative ionization mode? I saw an application note for EPA 539 by Agilent claiming the use of ammonium fluoride gave 7-11x better negative ionization sensitivity than the use of ammonium hydroxide (as per EPA 539).

http://www.chem.agilent.com/Library/app ... 2473EN.pdf

If you've used it, are there any precautions or admonishments about using it, like there are with TFA, in relation to LCMS? Any handling issues? Weird adducts I should be on the lookout for? Any issues about columns used with ammonium fluoride?

at the least, the usual concerns about fluoride exist: if you pump this into a waste pot that contains acid hplc waste (mobile phases with formic/acetic acids etc.), you will be making HF, and the glass bottle will gradually etch away.

It's also rather brave of Agilent to suggest using it with their triple quadrupole to look for problems; ammonium fluoride sublimes at high temperature (spray chamber!) to HF gas, according to Wikipedia, and that's not something I'd want in a mass spec (or anywhere). But if Agilent recommend it...

Well, they used a 1mM concentration at a flow rate of 0.3 mL/min in just the A reservoir, so I don't think we'd be generating a lot of hydrofluoric acid, so I'm not really worried about the source. I will, however, make a call to my instrument manufacturer to make sure they don't have some prohibition on using it that would void my service contract. My waste reservoir is plastic, so that's also not an issue. My solvent reservoirs are glass, but I think if I keep the pH where they did (6.2) I shouldn't really have much potential to create HF in the reservoir.

Zirchrom often suggests ammonium fluoride as a mobile phase additive with their columns (for peak shape in their case), I don't know if they show any MS applications with their columns, but it would be another place to check. To me, fluoride ion is a kind of bad place to go with MS, I've heard of people using perchlorate in MS, too...these would seem to be fine with other detectors.

Tread carefully and best wishes.

Well, AB Sciex got back to me. They had no specific admonitions regarding the usage of ammonium fluoride on my 4000. They said keep the concentration low and look for response loss, which may be indicative of a source cleaning, but otherwise, they didn't seem to think it was a big deal. I'll be trying it out on my Varian 1200 first, just to get a feel for the response changes of the various analyses I run, so we'll see how it goes.

We've used it on an Agilent 1946D with no problems. We do get significantly better negative sensitivity, as well as better positive sensitivity for certain pesticides.

We've used it on an Agilent 1946D with no problems. We do get significantly better negative sensitivity, as well as better positive sensitivity for certain pesticides.

Hi Mckrause,

Are you able to provide any further details regarding this analysis? What column do/did you use?

Thanks

Sounds promising. Also, what concentration?

Has anyone tried this additive and found it detrimental to silica based columns or glass capillaries over time??