LIM Ultrahigh Resolution Ion Mobility Spectrometry Separations of Isotopologues and Isotopomers Reveal Mobility Shifts due to Mass Distribution Changes
Roza Wojcik, Gabe Nagy, Isaac. K. Attah, Ian K. Webb, Sandilya V. B. Garimella, Karl K. Weitz, Adam Hollerbach, Matthew E. Monroe, Marshall R. Ligare, Felicity F. Nielson, Randolph V. Norheim, Ryan S. Renslow, Thomas O. Metz, Yehia M. Ibrahim and Richard D. Smith
The existing Drift Tube IMS (DTIMS) based isotopologue separations of sufficient resolving power (Rp) are largely impractical due to the large voltage drops and/or extremely long linear drift paths needed. The only other isotopologue or isotopomer ion separations which have been used previously is Field Asymmetric Ion Mobility Spectrometry (FAIMS). FAIMS also faces challenges of poor characterization, as well as issues relating to ion heating and potential structural perturbations due to the high fields used, as well as partial ion alignment in the field. This paper explores how MOBILion's SLIM technology helps in structural characterization of ions, as an alternative to FAIMS and DTIMS.
The paper, published in Analytical Chemistry concludes:
- In this paper, MOBILion's TW-based SLIM IMS technology was used to explore the benefits from the long and compact serpentine path lengths, where resolution has been shown to increase in proportion to the square root of path length.
- Isotopomers cannot be distinguished by MS alone since they have the same exact mass, unless fragment ions (e.g., obtained using MS/MS) reveal the sites of isotopic exchanges. Drift tube IMS (DTIMS) isotopologue separations of sufficient resolving power (Rp) are largely impractical due to the large voltage drops and/or extremely long linear drift paths needed.
- However,, directing the ions for additional passes through MOBILion's SLIM technology, using a Serpentine Ultralong Path with Extended Routing (SUPER) implementation, extends the path lengths achievable to >100 m, providing Rp (Resolving Power) up to âˆ¼1800, far greater than previously achievable with IMS.
- These measurements also benefit from the ability to inject very large ion populations via in-SLIM ion accumulation to provide significant ion signals after >1 km of SLIM SUPER IMS separations and improving the precision of mobility measurements achievable for higher Rp IMS measurements.
- The results show not only the utility of higher Rp IMS measurements, providing a greatly improved basis for understanding other factors contributing to an ion's Î© (collision cross section), but also a potential basis for new insights into gas phase ion interactions and new approaches for the structural characterization of gas phase ions.
- The paper, experimentally confirms the expectation that the increased Rp provided by MOBILion's SLIM SUPER IMS enables the separation of the naturally occurring isotopic peaks due to changes in reduced mass of the ionâˆ’molecule collision partners, as described by the Masonâˆ’Schamp relationship.
- There is a potential for utilizing any compound's naturally occurring isotopologues and isotopomers for such purposes with sufficient Rp and measurement dynamic range, which are significant attributes of SLIM IMS.
Analytical Chemistry 2019, 91, 18, 11952â€“11962 DOI: 10.1021/acs.analchem.9b02808