method switching

[smkh]

Dear All,

Any one have any idea if Ican I build afinal method on LC-MS/MS (API 5000 model) starting with apositive MRM mode then switch it to negative MRM mode.

another question if any one have any experience on analysis o f simvastain on negative MRM.

thanks alot

[sassman]

I haven't done it myself, but I am pretty sure that you can switch from pos to neg on an API 5000. It might not be possible in the same period since there will be a long delay between the scans, but surely you can do it in separate periods. Why not just give it a try?

Do you mean simvastatin? It doesn't look particularly good for negative esi. Have you tried both pos and neg modes?

[Schmitty]

Yes, you can. Just right-click and add a new period. Remember that there is a significant settling period when doing + and - at the same time.

[smkh]

Hi Sassman,

thanks alot for your replying
As you said it is done in seperate periods......
About simvastatin it gives apoor intensity in the neg mode but switching solve the problem.

Best regards.
smkh