IRMPD-MS ( Infrared Multiphoton Dissociation-Mass Spectrometry) di aggregati supremolecolari carichi positivamente di Bis (2-etilesil) solfosuccinato di sodio (AOTNa) in fase gas”

Gas Phase Charged Aggregates of Bis(2-ethylhexyl)sulfo-succinate (AOT) and Divalent Metal Ions. First evidence of AOT solvated aggregates

Assembling and chelating properties of sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) towards divalent metal ions have been investigated in the gas phase by electrospray ionization mass spectrometry. A variety of positively charged monometallated and mixed metal aggregates are formed. Interestingly, several ions contain solvent (MeOH, H2O) molecules and constitute the most abundant AOT cationic aggregates not containing sodium. These species are the first example of solvated AOT-metal ion aggregates in the gas phase. By increasing the surfactant aggregation number, the abundance of solvated species becomes lower than that of unsolvated ones. Decompositions of ionic species have been studied…

Do electrospray mass spectra of surfactants mirror their aggregation state in solution?

One important feature in the gas phase chemistry of surfactants is to ascertain whether their aggregates produced by electrospray ionization reflect those formed in the starting solution. With this aim, we have performed ESI-MS, ESI-MS/MS and ER-MS spectra of bis(2-ethylhexyl)sulfosuccinate (AOTNa) solutions in different solvents, i.e. water, water/methanol, methanol and n-hexane. The results clearly indicate that, notwithstanding the strongly different aggregation state in solution (direct micelles in water and in water/methanol, molecular dispersion in methanol and reverse micelles in n-hexane) and marked effects of the solvent polarity on the total ionic current, the surfactant aggregate…

Surfactant self-assembling in the gas phase: bis(2-ethylhexyl)- sulfosuccinate divalent metal ion anionic aggregates

RATIONALE: Investigation of fundamental aspects driving surfactant self-assembling and of the capability of including guest molecules or ions in their micellar aggregates is an exciting research field for theoretical and technological reasons. In this light, assembling and chelating properties of sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) towards divalent metal ion chlorides have been investigated in the gas phase by electrospray ionization mass spectrometry in negative ion mode, tandem mass spectrometry and energy-resolved mass spectrometry. METHODS:Water/methanol solutions of AOTNa and chloride salts of nickel, magnesium, calcium and manganese, with different AOTNa/metal salt ratios, …

Review: Mass spectrometry of surfactant aggregates

In contrast with the enormous amount of literature produced during many decades in the field of surfactant aggregation in liquid, liquid crystalline and solid phases, only a few investigations concerning surfactant self-assembling in the gas phase as charged aggregates have been carried out until now. This lack of interest is disappointing in view of the remarkable theoretical and practical importance of the inherent knowledge. The absence of surfactant–solvent interactions makes it easier to study the role of surfactant–surfactant forces in determining their peculiar self-assembling features as well as the ability of these assemblies to incorporate selected solubilizate molecules. Thus, th…

Micelle in fase gas: una nuova frontiera della spettroMetria di Massa

Synthesis and chemical characterization of CuII, NiII and ZnII complexes of 3,5-bis(20-pyridyl)-1,2,4-oxadiazole and 3-(20-pyridyl)5-(phenyl)-1,2,4-oxadiazole ligands

The synthesis and structural characterization of NiII, CuII and ZnII complexes of two chelating 1,2, 4-oxadiazole ligands, namely 3,5-bis(20-pyridyl)-1,2,4-oxadiazole (bipyOXA) and 3-(20-pyridyl)5- (phenyl)-1,2,4-oxadiazole (pyOXA), is here reported. The formed hexacoordinated metal complexes are [M(bipyOXA)2(H2O)2](ClO4)2 and [M(pyOXA)2(ClO4)2], respectively (M = Ni, Cu, Zn). X-ray crystallography, 1H and 13C NMR spectroscopy and C, N, H elemental analysis data concord in attributing them an octahedral coordination geometry. The two coordinated pyOXA ligands assume a trans coplanar disposition, while the two bipyOXA ligands are not. The latter result is a possible consequence of the format…

ION MOBILITY STUDIES ON SODIUM-BIS (2- ETHYLHEXIL)SULFOSUCCINATE (AOTNa) AGGREGATES

The supramolecular charged aggregates formed during ESI ionization of AOTNa solutions under critical micelle concentration have been studied thorough ion mobility experiments. In particular, positively charged clusters with several charge states, ranging from +1 to +4, have been investigated. It has been found that, despite to previous investigations (Siuzdak et al. 1995, Nohara et al. 1998), specific ionic aggregates with a peculiar cross section are observed. Indeed a single drift time is observed for each charged aggregate. Using both calculated cross section and experimental calibration curves the experimental cross section of the observed cation has been determined. It is worth noting …

NEW INSIGHTS ON SUPRAMOLECULAR AGGREGATES OF SODIUM DOCUSATE (AOTNa) BY ION MOBILITY MASS SPECTROMETRY

Backgorund: The ability of some surfactants to form charged aggregates in gas phase has been proven experimentally by electrospray ionization (ESI) spectrometry [1- 5]. However, in the early investigations, interesting questions concerning the structural organization of these aggregates in gas phase and if they reflect their typical self-assembling in the starting liquid solutions were not addressed. Subsequently, independently of their aggregation motive in liquid phase and of the charge state in the gas phase, some hints suggesting that surfactant molecules are organized in gas phase as reverse micelle-like aggregates have been reported Objective: The supramolecular charged aggregates for…

Surfactant Self-Assembling in the Gas Phase:bis(2-ethylhexyl)sulfosuccinate-Metal Ion Aggregates

Surfactant self-assembling in gas phase: positively monocharged sodium alkanesulfonate clusters

Spatially ordered surfactant assemblies in the gas phase: negatively charged bis(2-ethylhexyl)sulfosuccinate- alkaline metal ion aggregates

The formation and structural features of negatively charged aggregates of sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) surfactant molecules in the gas phase have been investigated by electrospray ionization mass spectrometry (ESI-MS) and density functional theory calculations. Mainly driven by the interactions of alkali metal ions both with the oxygen atoms of the sulfonate group and with the succinate moiety of the AOT(-) anion, spatially ordered supramolecular assemblies, characterized by an internal core composed of surfactant counterions and hydrophilic head groups surrounded by the surfactant alkyl chains pointing outwards, are formed. Calculations have shown that surfactant self-org…

Supramolecular surfactant aggregates in gas-phase:monocharged sodium alkanesulfonate clusters

Francesistica. Bibliografia delle opere e degli studi di letteratura francese e francofona in Italia. 1995-1999

Bibliografia delle opere e degli studi di letteratura francese e francofona in Italia