ESI-MS in negative ion mode

Katheryn Resing (Katheryn.Resing@Colorado.EDU)
Wed, 28 Jul 1999 12:21:36 +0000

I do negative ion at neutral pH, using 50 mM triethylamine adjusting to pH
7 with CO2 (use a bubbler charged with dry ice), and acetonitrile buffers.
You can use a poros resin, or use a silica base resin, but for silica put
in a filter column before the injector to help stabilize the resin at the
neutral pH.

We also have fine results with negative ion maldi. We "step" the voltages
to prevent discharge.

Detectors on some mass spectrometers are less sensitive in negative ion mode.

Katheryn