Re: MassSpec: LCQ

Steven Howell (showell@nimr.mrc.ac.uk)
Wed, 08 Dec 1999 17:39:19 +0000

>What's the best combination of parameters (voltages and capillary temp) to
>promote formation of doubly charged ions in nanospray MS? I get quite a few
>singly charged ions in the 1000-2000 m/z range whose 2+ states can be found
>on zoomscan but which are not obvious by inspection of the full scan. What
>tricks favour the higher charge state? I'm spraying in 1% formic acid, 70%
>MeOH.

I've found concentration has a big effect on charge distribution for
tryptic digests. If there are large peaks for 1+ species then diluting the
sample will result in a relative increase in the 2+ peaks in my hands
(typical conditions 800V, 200degC, 1% formic 60% MeOH). Whether the
absolute intensities of the 2+ ions change I have not checked, but the 2+
ions are much easier to find.

regards

Steve Howell

__________________________________________________________
Dr Steven A. Howell
Laboratory of Protein Structure
National Institute for Medical Research
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