LC/MS/MS (ESI)-When is it appropriate to quantify Na adduct?

[MMJ88]

Thanks for your input, Klaus. I'm returning to this project soon, and will be doing some MS optimization again as I'm trying to add some additional compounds to the method. I'll keep an eye out for that possibility.

[cdean]

I've been running LCMS methods for Paclitaxel for almost a decade. About 90% of the time as a Na adduct, on Sciex 4000 and 5000 instruments. For some odd reason I've never been able to figure out, I have one instrument with much better response as M+H

I've never had issues with the Na adduct using a labeled internal standard. However, I did have one project where I used an analog internal standard that did not ionize as a Na adduct. It had pretty bad injection reproducibility, but that was only one study out of almost 100