Generation of gas‐phase zirconium fluoroanions by electrospray of an ionic liquid. (20th April 2014)

• Record Type: Journal Article
• Authors: Groenewold, Gary S.; Delmore, James E.; Benson, Michael T.; Tsuda, Tetsuya; Hagiwara, Rika
• Is Part Of: Rapid communications in mass spectrometry. Volume 28:Number 11(2014)
• Page Start: 1233
• Page End: 1242
• Publication Date: 2014-04-20
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.6890
• Languages: English
• ISSNs: 0951-4198

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="rcm6890-sec-0001" sec-type="section"> <title>RATIONALE</title> <p>New approaches for forming anions are sought that have strong abundance and no isobaric overlap, attributes that are compatible with the measurement of isotope ratios. Fluoroanions are particularly attractive because fluorine is monoisotopic, and thus will not have overlapping isobars with the isotope of interest. Since many elements do not have positive electron affinity values, they do not form stable negative atomic ions, and hence are not compatible with isotope ratio measurement using high sensitivity isotope ratio mass spectrometers such as accelerator mass spectrometers.</p> </sec> <sec id="rcm6890-sec-0002" sec-type="section"> <title>METHODS</title> <p>Zirconium fluoroanions were prepared using the fluorinating ionic liquid (IL) 1‐ethyl‐3‐methylimidazolium fluorohydrogenate, which was used to generate abundant [ZrF<sub>5</sub>]<sup>−</sup> ions using electrospray ionization. The IL was dissolved in acetonitrile, combined with a dilute solution of either Zr<sup>4+</sup> or ZrO<sup>2+</sup>, and then electrosprayed. Mass analysis and collision‐induced dissociation experiments were conducted using a time‐of‐flight mass spectrometer. Cluster structures were predicted using density functional theory calculations.</p> </sec> <sec id="rcm6890-sec-0003" sec-type="section"> <title>RESULTS</title> <p>The fluorohydrogenate IL solutions generated abundant [ZrF<sub>5</sub>]<sup>−</sup> ions starting from solutions of both Zr<sup>4+</sup> and ZrO<sup>2+</sup>. The mass spectra also contained IL‐bearing cluster ions, whose compositions indicated the presence of [ZrF<sub>6</sub>]<sup>2−</sup> in solution, a conclusion supported by the structural calculations. Rinsing out the zirconium‐IL solution with acetonitrile decreased the IL clusters, but enhanced [ZrF<sub>5</sub>]<sup>−</sup>, which was sorbed by the polymeric electrospray supply capillary, and then released upon rinsing. This reduced the ion background in the mass spectrum.</p> </sec> <sec id="rcm6890-sec-0004" sec-type="section"> <title>CONCLUSIONS</title> <p>The fluorohydrogenate‐IL solutions are a facile way to form zirconium fluoroanions in the gas phase using electrospray. The approach has potential as a source of fluoroanions for isotope ratio measurements, which would enable high‐sensitivity measurement of minor zirconium isotopes without overlapping isobars caused by the charge carrier (i.e., the monoisotopic fluorine atoms). Copyright © 2014 John Wiley & Sons, Ltd.</p> </sec> </abstract>