The week doubly charged ions may be more a function of the solvent you are
spraying. You might find that you get more charging by cutting back on the
formic acid concentration. We typically use 0.1-0.2% formic or 1-2% acetic
acid. You will also see less charging out of 0.1% TFA relative to 0.1% formic
or 1% acetic. If you are infusing or nanospraying your sample, a capillary
temperature of 150-200C should be the optimum range. Capillary and tube lens
offset values would probably optimize around zero (plus or minus 10 or 20V)
under these conditions. These conditions are for an LCQ classic, the deca
capillary would probably be run a little hotter (e.g., 250C). Hope that helps.
Regards,
Mark Hail
Bristol-Myers Squibb
Len Packman wrote:
> A question for experienced LCQ users:
>
> 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.
>
> Len
>
> *********************************************************************
> Dr Len C. Packman
> Assistant Director of Research
> Protein and Nucleic Acid Chemistry Facility
> Department of Biochemistry
> University of Cambridge
> 80 Tennis Court Road
> Old Addenbrookes Site
> Cambridge, CB2 1GA, UK
> Tel: +44 (1223) 333639
> FAX: +44 (1223) 766002
> e-mail: lcp2@mole.bio.cam.ac.uk
> Visit my WWW page at http://www.bio.cam.ac.uk/proj/adr/PNAC/pnac.html