title: Investigations of cluster ions formed between cesium cations and benzoic, salicylic and phthalic acids by electrospray mass spectrometry and density-functional theory calculations. Toward a modeling of the interaction of Cs+ with humic substances.
abstract: A concerted theoretical (density-functional theory) and experimental electrospray mass spectrometry study was conducted on the formation of cesium cation adducts with small molecules taken as models of specific interactions sites in humic substances. Electrospray experiments with phenol, benzoic acid, salicylic acid, and phthalic acid, in methanolic solution containing cesium nitrate, were performed using a quadrupole ion trap. The formation of positively charged mixed clusters, [Cs(CsNO3)(n)(CsA1)(m)(Cs2A2)(p)]+ (A1 = benzoate, salicylate, and hydrogenophthalate, A2 = phthalate), was observed. Calculations of structures and bonding energetics of Cs+ in simple adducts formed with NO3-, CsNO3, A-, AH, and CsA are reported. The observation of variable cluster stoichiometry (n, m and p values) was interpreted in terms of more or less favorable interaction energies between Cs+ and the neutral species constituting the clusters. Phenol did not form clusters in significant abundances, despite a strong calculated interaction between Cs+ and cesium phenolate. This was attributed to its weak acid dissociation in the electrospray solution.
authors.affiliation: Laboratoire de Radiochimie, Sciences Analytiques et Environnement, and GUMPAC-Spectrométrie de Masse, Faculté des Sciences, Université de Nice Sophia-Antipolis, Parc Valrose, 06108 Nice Cedex 2, France.
authors.forename: Pierre-Charles
authors.initials: PC
authors.lastname: Maria
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Gal
authors.forename: Lionel
authors.initials: L
authors.lastname: Massi
authors.forename: Peeter
authors.initials: P
authors.lastname: Burk
authors.forename: Jaana
authors.initials: J
authors.lastname: Tammiku-Taul
authors.forename: Sven
authors.initials: S
authors.lastname: Tamp
mesh_terms: D000146:Acids, Carbocyclic / Q000737:chemistry*; D019817:Benzoic Acid / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D002586:Cesium / Q000737:chemistry*; D006812:Humic Substances; D008956:Models, Chemical; D010795:Phthalic Acids / Q000737:chemistry; D020156:Salicylic Acid / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D000146:Acids, Carbocyclic; D002412:Cations; D006812:Humic Substances; D010795:Phthalic Acids; D002586:Cesium; C032279:phthalic acid; D019817:Benzoic Acid; D020156:Salicylic Acid