Atmospheric pressure ionisation mass spectrometric fragmentation pathways of noscapine and papaverine revealed by multistage mass spectrometry and in‐source deuterium labelling

Two opium alkaloids, noscapine and papaverine, show good response as [M+H] + ions in positive ion electrospray mass spectrometry and atmospheric pressure chemical ionisation mass spectrometry. The two compounds exhibit markedly different fragmentation pathways and behaviour under multistage mass spectrometry (MS n ), with papaverine displaying a wealth of ions in MS 2 and noscapine providing a single dominant ion at each stage of MS n prior to MS 4 . Elucidation of the fragmentation pathways using the MS n capability of the ion trap was aided by spraying the analytes in 2 H 2 O to incorporate an isotopic label. Simplex optimisation allowed optimum trapping and fragmentation parameters to be determined, leading to a six‐fold improvement in response for one transition and a seven‐fold improvement for one transition sequence. Copyright © 2006 John Wiley & Sons, Ltd.