Sensitive and qualitative analysis of isomeric and isobaric plant metabolites was achieved by developing a MRM and MRM-dependent product ion scan
Each fragment, isolated from the product ion scan
, was fragmented again in the LIT to look for secondary ion candidates.
For pseudo-[MS.sup.3], an initial MS2 scan followed by a product ion scan
of each compound was performed to distinguish the parent ion peaks as well as the fragment ions of compounds 4a-j.
An initial MS/MS scan followed by a product ion scan
of each compound was performed to distinguish the parent ion peaks and the fragment ions of compounds 3a-h.
For example, the definition of "product ion scan
' is repeated twice, whereas the term "product ion' is not actually defined.
They include product ion scans
to detect expected metabolites, as well as precursor ion scans and neutral loss scans to detect both expected and unexpected metabolite ions.
A maximum of 4 candidate ions were selected for subsequent product ion scans
based on signal intensity.
Product ion scans
of VMA and [d.sub.3]-VMA calibrators were collected in continuous flow mode as described previously (4,5).
MS/MS product ion scans
of MMA and succinate standards were collected in continuous flow mode by connecting an infusion pump directly to the TurboIonSpray probe.