hi all,

I'm developing a method (my first LC-MS/MS method) for quantification of beta alanine. Working with standards, I got a nice calibration curve (10 times the requested sensitivity).

All of the sudden (after about 100 runs) I lost the signal, the noise increased and the chromatogram look like a baseline. I tried flow injection just to see a peak, but I only saw noise.

At this point we had problems with the instrument (not related to the analysis -was the pump-) and right after the repair we had a scheduled a PM).

After this, I tried the method again and it was ok. But, after about 20 runs the baseline started degrading again (in this case it's showing ghost peaks and there is a 'negative' peak right before the beta alanine peak) and I'm loosing sensitivity for the lower concentrations.

I don't know much about triple quad, but is it possible that the mass analyzer is getting saturated with b-alanine (b-alanine getting stick to the quads, or something like that)?

I'd appreciate any thoughts and advices,

thanks
Sergio