In protein analysis we use milliQ water/Acetonitrile with 0.1% TFA (but TFA tends to suppress the MS signal, so you should use 0.05% or less).

I think you should try 0.1% Formic Acid. It will probably give you slightly lower resolution of peaks but a stronger MS signal.

Hi Aimee, here are lists of volatile buffers, I hope it helps.

http://www.nestgrp.com/protocols/trng/buffer.shtml

http://wolfson.huji.ac.il/purification/buffers/Volatile_buffer.html

https://www.applichem.com/fileadmin/Broschueren/BioBuffer.pdf