a interesting question about tripquad

[meillid]

Hi, when trying to use isotope as inter. std, a interesting question come into my mind. Under MRM mode, if the parent ions of analyte and internal Std have different masses(e.g. isotope labled for the internal std), the daughter ions which was selected to monitor have same masses however(e.g. the selected fragment is not isotope labeled for the internal std). Could the instrument distinguish them and give correct analysis? Thanks.

[Kostas Petritis]

Normally you should be able to so as the collision cell is emptied before selecting the next ion for fragmentation. That said, there is always the problem of cross-talk that happens exactly at the cases you mention. There are solutions for that though, you can either use a higher pause time or maybe the best one is to use a phantom MRM transition between these two i.e. something with a parent and daughter ion totally unrelated with your analytes...

New generation mass spectrometers have smaller problems of cross-talk than older generations...