Last week, we highlighted the unique benefit of the eight SIFT-MS reagent ions (H3O+, NO+, O2+, O–, O2–, OH–, NO2–, and NO3–) for rapid, comprehensive gas analysis.
This week, we consider another important benefit that the eight reagent ions provide: unsurpassed real-time selectivity.
Real-time selectivity in SIFT-MS is achieved by combining two independent features:
- diverse chemical ionization mechanisms, which are characteristic of the reagent ions, and
- instantaneous reagent ion switching, which is achieved by the first quadrupole mass filter.
The table below summarizes the reaction mechanisms of the SIFT-MS reagent ions in general terms. For a particular reagent ion, one finds that a compound usually reacts via just one or two mechanisms. These mechanisms tend to be consistent across the class of compounds (e.g. aldehydes behave consistently), but they differ between classes.
Couple this reaction chemistry with instantaneous reagent ion switching and the result is real-time separation of isobars and isomers, plus the option to use the most sensitive and selective reagent ion for each target compound.
For example, consider analysis of flavor volatiles on breath. The graph below shows data in which both H3O+ and NO+ were used to analyze volatiles released from mint-flavored gum as it was chewed.
Eight rapidly switchable reagent ions – with their unique reaction chemistry for a particular compound – gives SIFT-MS unsurpassed selectivity for applications that require continuous or high-throughput analysis.
SIFT-MS is unique. Selectivity + Sensitivity + Speed = Your Opportunity.