Electrospray Ion Mobility Mass Spectrometry of positively and negatively charged (1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide aggregates

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Abstract

RATIONALE: Self-assembling processes of surfactants in the gas phase constitute a developing research field of interestsince they allow information to be gained on the peculiar structural organization of these aggregates, on their ability toincorporate from small molecules up to proteins and on their possible use as carriers of drugs in the gas phase or ascleaning agents and exotic reaction media.METHODS: The mass spectra of charged aggregates of the chiral surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) in the gas phase have been recorded using a Synapt G2-Simass spectrometer in the positive and negative ion mode. For comparison purposes, the mass spectra of sodiumbis(2-ethylhexyl)sulfosuccinate and sodium octane sulfonate aggregates have also been recorded under the sameexperimental conditions. The collisional cross sections of positively and negatively charged DMEB aggregates wereobtained through an appropriate calibration of the measured drift times.RESULTS: For all the surfactants investigated, it has been found that there is a lowest and a highest limit of theaggregation number at each charge state: no aggregates are found outside this range. Moreover, the occurrence at eachaggregation number and extra charge of a unique value of drift time points toward aggregates whose conformationsdo not show discernible shape change in the experiment time scale. The analysis of the collisional cross sectionsemphasizes that the DMEB aggregates are nearly spherical clusters somewhat affected by the charge state andconstituted by interlaced polar and apolar domains.CONCLUSIONS: The analysis of all the experimental findings indicates that in the gas phase DMEB formssupramolecular aggregates characterized by an internal organization whose stability is triggered by the charge state.The comparison of the behavior of DMEB aggregates with that of sodium bis(2-ethylhexyl)sulfosuccinate and sodiumoctane sulfonate aggregates allows us to highlight the effects on the aggregate organization in gas phase due to natureof the head group and alkyl chain steric hindrance.
Original languageEnglish
Pages (from-to)230-238
Number of pages9
JournalRapid Communications in Mass Spectrometry
Volume30
Publication statusPublished - 2016

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry

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