CCS, derived from IMS, is a robust physiochemical property of an ion. Time with drift (IMS) alignment provides simplified spectra.
Companies and regulatory authorities are under pressure to develop screening methods to detect a broad spectrum of contaminants. Many are turning to High Resolution MS (HRMS). Improvements in sensitivity with highly selective acquisitions, such as utilizing ion mobility (IMS), allow users to expand the scope of current targeted methods, plus characterize unknowns. Modern, non-targeted, HRMS screening methods can, in one run, collect accurate mass spectra with isotopic fidelity for precursor and product ions, collisional cross section, along with sufficient points across a UPLC chromatographic peak to perform quantification. Here, we demonstrate how routine ion mobility and modern informatics can be used to comprehensively screen four different food matrices and assist with unknown elucidation from a complex data set.
Matrix extracts of French Cut Green Beans, Jalapeno Peppers, Mini Sweet Peppers, and Strawberries were analyzed for incurred residues using a Waters Vion Ion Mobility enabled QTof. All four samples were run in triplicate at 1µL and 5µL injection volumes. Scan Time was 0.25 sec over a mass range of 50-1200 Da. In order to show that collisional cross section (CCS) is a robust and independent physiochemical property of an ion, the LC method was performed with two different columns and mobile phases generating different retention times for each compound studied in the targeted analysis. Utilizing IMS for spectral cleanup is shown to improve specificity for both target screening as well as structural elucidation of unknowns.
Collisional cross section, a unique measurement derived from ion mobility separation, allowed additional criterion for the search of targeted analytes. The added peak capacity and spectral cleanup not only increased selectivity and confidence in the target matches but also simplified spectra for non-targeted (unknown) masses of interest. Nearly 200 pesticide residues with CCS values ranging from 118-307 Ǻ2, mass ranging from 141-1008 Da., and over 8 different concentrations were analyzed. Results indicated <1% RSD in CCS values for each compound. For targeted screening of the fruit and vegetable samples, time and IMS drift alignment were shown to provide “spectral cleanup” for more accurate and simplified searching. Spectral cleanup from an unknown candidate peak also allowed simplified online searching. The candidate was identified as Flupyradifurone, a recently manufactured butenolide insecticide. Identification was supported by the use of halogen match and common fragment searching, based on structural characteristics shared with Imidacloprid, which Flupyradifurone was manufactured to replace.