Perspectives
Our results show that high resolution exact mass GC-MS can be used in
plants, as an efficient way to carry out metabolic profiling. This
technique shows several advantages over classical, nominal mass GC-MS,
such as identification less prone to errors thanks to exact mass m/z
features. The database we propose here to perform targeted analyses
covers more than 200 metabolites of different chemical families. This
database is evolutive, in that it will be enriched over the coming years
and updated versions kept accessible via the journal website. We
recognise that plants contain a lot of sugars, with many isomers. Some
of them have identical retention times, and thus cannot be resolved with
exact mass since m/z features have the same elemental composition. To
solve this problem, specific devices like ion mobility may be required
(Morrison & Clowers, 2018; Mu, Schulz, & Ferro, 2018; Przybylski &
Bonnet, 2021). In terms of isotopic analysis via exact mass GC-MS, Si
isotopes represent a limitation to distinguish isotopologues. We showed
that high mass precision allows reasonable access to34S isotopologues, but less so for15N or 33S that are much less
abundant. When isotopic enrichments are modest, GC-C-IRMS analysis is
the best alternative, but this technology is presently not able to
perform 34S analysis. Therefore, exact mass LC-MS
seems to be better suited to isotopic analysis of sulphur-containing
compounds.