pH effect on Evaporative Light Scattering?

[Ryans17]

Hello:

Recently I've been told by a colleague that mobile phases with a pH above 8 would be a problem when using ELSD.

Does anyone know if this is true, why that would be the case (theory) and if they've seen any literature discussing this?

thanks

[Consumer Products Guy]

For ELSD (like for LCMS) you need to use volatile buffers, such as an amine in your case.

[Ryans17]

So, Ammomium Hydroxide wouldn't be good with ELSD?

[nwashburn]

It should be fine to use ammonium hydroxide, it is a volatile base. Sodium hydorixde wouldn't work but the ammonia should be no problem. Just out of curiosity what type of separation are you using w/ the ELSD? I have been working on an AEX method to transfer from UV to ELSD and I am interested to see what others have come up w/ for this separation w/ the ELSD.

[Kostas Petritis]

Ryans17,

There is no correlation between the mobile phase pH and what is or not compatible with the ELSD. This detector just need a volatile mobile phase which is independant of the mobile phase pH...

[Bill Tindall]

Maybe the folklore about not using buffers above pH 8 came from a case where high pH was dissolving a column packing and the silica was showing up as a signal. Or the high pH was dissolving something in the detector. As others have already stated, there is nothing inherent about pH 8 that is bad.