title: ESI activity of Br⁻, BF₄⁻ , ClO₄⁻ and BPh₄⁻ anions in the presence of Li⁺ and NBu⁴⁺ counter-ions.
abstract: To improve our understanding of the electrospray ionization (ESI) process, we have subjected equimolar mixtures of salts A+X-(A+= Li+, NBu4+; X-= Br-, ClO4-, BF4-, BPh4-) in different solvents (CH3CN, tetrahydrofuran, CH3OH, H2O) to negative-ion mode ESI and analyzed the relative ESI activity of the different anionic model analytes. The ESI activity of the large and hydrophobic BPh4-ion greatly exceeds that of the smaller and more hydrophilic anions Br-, ClO4-and BF4-, which we ascribe to its higher surface activity. Moreover, the ESI activity of the anions is modulated by the action of the counter-ions and their different tendency toward ion pairing. The tendency toward ion pairing can be reduced by the addition of the chelating ligands 12-crown-4 and 2.2.1 cryptand and is, although to a smaller degree, further influenced by the variation of the solvent. Complementary electrical conductivity measurements afford additional information on the interactions of the ionic constituents of the sample solutions. Copyright © 2017 John Wiley & Sons, Ltd.
authors.affiliation: Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany.
authors.forename: K
authors.identifier: 0000-0001-7352-5789
authors.initials: K
authors.lastname: Koszinowski
authors.affiliation: Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstr. 2, 37077, Göttingen, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Lissy
keywords: aggregation; counter-ion; electrical conductivity; electrospray ionization; solvent effects