Questions about LC-Ms buffers

[zsolt.bodai]

Hello Everybody,

I have two short question about LC-MS buffers.
1. What is the maxiumum concentration of NH4Acetate or formiate that you use in the eluent? And why? (I have never used more than 20 mM)
2. Why can buffers improve the peak shape some of the compounds?

Many thanks in advance,
Zsolti

[schlepro]

Dear Zsolti,

1). Amm. Ac & Amm. Formate are MS compatible. I've never had to worry about their max molarity. I know someone who just ran 200mM Amm. Formate on a QTOF and it was fine. I typically stay under 15mM based on some vague notion that it is easier on my system.

2). One reason is that the tendency for compounds to resolve (e.g you get a peak vs. a smear vs. nothing), in part, is pH dependent.

Sincerely,
Keith