Chromatography Forum

Hello. I am new to practical MS work. I have taken some courses about theory and data interpretation but do not have much real experience running the mass spec to obtain the data.

I work for a small company and we have an old Sciex API365 that I am in charge of getting up and running as well as trying to obtain data from. I have cleaned it and have it running but now I need some help from there.

At this point the work I would be doing would be direct infusion of a single peptide soln or a collected fraction using ESI-MS. My samples are typically dissolved in 10% ACN / 90% H2O. Do I need to add some formic acid before i do the direct injection? If I am just using "generic" ESI parameters, would I still see a signal even if the parameters are not optimized?

Any suggestions would be appreciated. Also if anyone has any suggestions on books that might be helpful to someone very new to the practical aspects of MS, I would appreciate that too.

Thanks!

You should indeed see some background signal, especially if you scan a range (MS scan or Q1 scan) say from 50 AMU to a few hundred. Just running some methanol/Aq. ammonium actetate should give a god signal at m/z 59.

If the analyte you plan to look at is ionizable you have a good chance of seeing it if your system parameters are reasonable. You want the declustering potential high enough to break up any M+Cluster+ to M+H (example for positive mode) but you do not want it so high as to fragment sensitive compounds before they reach Q0.

Higher organic percent mobile phases tend to increase analyte signal when using ionspray/electrospray. I would think that 90% aqueous could be a problem (unless you are using APCI mode). Ionspray tends to work better with more organic (methanol or ACN). It also helps to put some formic acid (0.1% in water or so) or Ammonium Formate or Ammonium Acetate in the mobile phase for both positive or negative modes.

Keep the spray from the ionspray directed away from the orifice. You do not want to spray directly into the orifice, system contamination can result.


You might try

http://books.google.ca/books?id=EcaKuhf ... 00&f=false

to get started with.

Alp


Good luck.

Sorry,
Should read:

Just running some Acetonitrile/Aq. ammonium actetate should give a good signal at m/z 59, positive ion mode.

m/z 59 is also seen from acetate ion in negative mode.

hey,
i am new usar of HPLC-ESI MS, i never work on that mashine before, and no one in company work on that mashine so i am on my own and i will be grateful for all help. I have probleme already in beggining and problem start with ionization sulphonated melamine- formaldehiyde resins. Resin is solvable in H20, i take 1% of that sample solution and diluted MeOH, but still nothing useful . Can someone halp me, what to do to get any ionization i will be really gratefull.
Or after i solve that i probleme i have to develop method, have anyone some ideas about wich HPLC-column, mobil phase...

thanks