Rapid paper spray mass spectrometry characterization of uranium and exemplar molecular species

Abstract

Rationale:The ability to detect and quantify the presence of specific inorganic elements and complexes is essential for environmental monitoring and nuclear safeguards applications. In this work, paper spray ionization mass spectrometry was used for the rapid chemical and isotopic characterization of trace inorganic species collected on cotton swipe substrates. The direct analysis of cotton swipes using this ambient ionization technique led to fast sample analysis that retained original chemical information of the source material with minimal sample preparation.Methods: Mass spectra were collected with an atmospheric pressure ionization, high-resolution mass spectrometer for solutions containing uranyl acetate, uranyl chloride, uranyl nitrate, and uranyl tri-n-butylphosphate complexes. Gadolinium nitrate was used as an internal standard for the quantitative analysis of uranium. To demonstrate the ability to characterize inorganic contaminants in the presence of uranium, a multi-element inorganic standard containing U, Bi, Pb, Cd, Fe, and Zn was deposited onto cotton substrates and directly analyzed without purification.Results: All elements doped on the cotton substrate were detected with strong signal-to-noise ratios (ca 1000 for UO 2 + on multi-element doped swipes) and high integrated intensities (>10 5 counts) from collection periods of approximately 1 min.Limits of detection were determined to be approximately 94 ng for UO 2 + and uranyl acetate through the measurement of ppb level solutions. Conclusions:The rapid analysis of uranium and other inorganic-containing samples while still retaining original chemical information (e.g. uranyl complexation) was demonstrated. Qualitative detection and speciation were achieved in less than 1 min of analysis. For uranium isotopic quantitation, longer accumulations (>15 min) can be sustained to improve the accuracy of minor 235 U isotopic abundance measurements to approximately 1% error.

Matrix-Assisted Ionization of Molecular Uranium Species

“…More recently, paper spray ionization (PSI) MS has been employed to analyze inorganic species [31][32] , including uranyl complexes 33 . By virtue of soft ionization, these ambient MS methods can generate uranyl ion species with intact ligands and potentially allow for identification of the progenitor chemical composition prior to dissolution [34][35][36] .…”

“…These methods offer the advantages of rapid analysis, soft ionization, and the potential to minimize current MS sample process requirements and instrumentation overhead burdens. Electrospray ionization (ESI) MS, a type of ambient MS, has been used since the 1990s to analyze inorganic compounds in solution, − including uranium species. − ESI has been used extensively to investigate the coordination chemistry of uranyl ligand complexes in the gas phase via collision-induced dissociation (CID), ,− , ion-molecule reactions, − , and spectroscopic techniques. ,, More recently, paper spray ionization (PSI) MS has been employed to analyze inorganic species, , including uranyl complexes . By virtue of soft ionization, these ambient MS methods can generate uranyl ion species with intact ligands and potentially allow for identification of the progenitor chemical composition prior to dissolution. − …”

“…Electrospray ionization (ESI) MS, a type of ambient MS, has been used since the 1990s to analyze inorganic compounds in solution, − including uranium species. − ESI has been used extensively to investigate the coordination chemistry of uranyl ligand complexes in the gas phase via collision-induced dissociation (CID), ,− , ion-molecule reactions, − , and spectroscopic techniques. ,, More recently, paper spray ionization (PSI) MS has been employed to analyze inorganic species, , including uranyl complexes . By virtue of soft ionization, these ambient MS methods can generate uranyl ion species with intact ligands and potentially allow for identification of the progenitor chemical composition prior to dissolution. − …”

“…20,29,30 More recently, paper spray ionization (PSI) MS has been employed to analyze inorganic species, 31,32 including uranyl complexes. 33 By virtue of soft ionization, these ambient MS methods can generate uranyl ion species with intact ligands and potentially allow for identification of the progenitor chemical composition prior to dissolution. 34−36 Ambient MS methods based on matrix-assisted ionization (MAI) have not seen any exploratory effort for uranium species detection and analysis, though there has been extensive research on organic analysis in the brief time since its discovery.…”