Page 1 of 1
pH effect on Evaporative Light Scattering?
Posted: Thu Jan 27, 2005 3:54 pm
by 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
Posted: Thu Jan 27, 2005 8:03 pm
by Consumer Products Guy
For ELSD (like for LCMS) you need to use volatile buffers, such as an amine in your case.
Posted: Thu Jan 27, 2005 8:44 pm
by Ryans17
So, Ammomium Hydroxide wouldn't be good with ELSD?
Posted: Thu Jan 27, 2005 8:54 pm
by 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.
Posted: Thu Jan 27, 2005 11:55 pm
by 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...
Posted: Fri Jan 28, 2005 9:12 pm
by 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.