Les intervenants > Mounier Lionnel

Orbitrap Isotope Ratio MS is becoming increasingly accepted in the community as a unique and complimentary approach to classical IRMS techniques for measuring relative abundances of isotopically substituted species. Electrospray ionization offers the specific advantage of performing “soft” ionization, which produces intact molecular ions and provides unique insight into the molecular anatomy of polar compounds in aqueous solutions. In contrast to classical approaches, no chemical manipulation or gas conversion reactions are required and as a result, no intramolecular information is lost from sample to analysis. Similar to classical approaches, the principles of identical treatment and rigorous sample standard bracketing have been retained and are the key to achieving precise and accurate relative abundance measurements.

Currently, this approach is being applied to oxyanions and small organic molecules. Utilizing the high resolution capabilities of the Thermo Scientific™ Orbitrap Exploris™ MS platform, resolving singly and doubly substituted isotopologues molecular ions is achieved in routine measurements. Methods have been developed for nitrate (δ15Ν, δ18O, δ17O, Δ17O, Δ15N18O, Δ15N17O, Δ18O18O), sulphate (δ33S, δ34S, δ36S, δ17O, δ18O, Δ17O, Δ33S, Δ36S, Δ34S17O, Δ33S18O, Δ34S18O, Δ17O18O, Δ18O18O), phosphate (δ18O, δ17O, Δ17O, Δ17O18O, Δ18O18O), which achieve sub-‰ precision for isotope ratios of singly substituted isotopologues. We are actively developing methods for small organic molecules such as MSA, caffeine, vanillin and amino acids. We will present an overview of sample introduction, methods and measurement approaches.