Development of Direct Injection/Ionization Mass Spectrometry Methods for Whole Molecule Characterization

Abstract

The objective of this work is to adapt ambient ionization mass spectrometry (AMS) techniques for the rapid analysis of intact uranium complexes, stable strontium, cerium, and explosive compounds. The methods used were "soft ionization" techniques, which facilitate the detection of whole molecule complexes. The soft ionization mass spectrometry (MS) techniques that were investigated include paper spray ionization (PSI), matrix-assisted ionization (MAI), electrospray ionization (ESI) and direct analysis in real time (DART). For the first time, PSI-MS methods were successfully developed for whole molecule uranium-containing analytes (uranyl acetate, uranyl nitrate, and uranyl-tributylphosphate complexes). This was also the first demonstration of uranium complex detection and characterization and one of the few examples of inorganic analysis using MAI techniques. Proof of concept experiments also putatively identified matrix-derived ions and ion complexes that have not previously been described in the literature. Additionally, PSI-MS on cotton swipe samples doped with a multi-element standard containing µg levels of U, Bi, Pb, Cd, Fe, and Zn were directly analyzed without purification, representing a major improvement over existing methods. Both PSI and MAI methods demonstrated limits of detection (LODs) in the 10-100's ng for various uranyl species within a range of 10's ppm-100's ppb, dependent on analytical method and analyte species. AMS methods were also developed for other inorganics, including Ce and Sr, and organic explosive residues to address specific challenges in environmental monitoring and forensics. Further refinement and qualification of the AMS techniques developed within this effort would lead to significant cost reduction and timeliness by facilitating the triage and queueing of samples for subsequent more sensitive and time-consuming analyses. Awards and Recognition One manuscript has been submitted to the peer-reviewed Journal of the American Society for Mass Spectrometry titled "Matrix Assisted Ionization of Molecular Uranium Species". A manuscript on the rapid detection of inorganic Strontium and Cerium species by ambient mass spectrometry techniques is in preparation and will be submitted to Journal of the American Society for Mass Spectrometry. Intellectual Property Review This report has been reviewed by SRNL Legal Counsel for intellectual property considerations and is approved to be publicly published in its current form.