title: Characterization of polysorbate 85, a nonionic surfactant, by liquid chromatography vs. ion mobility separation coupled with tandem mass spectrometry.
abstract: Liquid chromatography (LC) and ion mobility (IM) separation have been coupled with mass spectrometry (MS) and tandem mass spectrometry (MS(2)) to characterize a commercially important nonionic surfactant, polysorbate 85. The constituents of this amphiphilic blend contained a sorbitan or isosorbide core that was chain extended with poly(ethylene oxide) (PEO) and partially esterified at the PEO termini with oleic acid or, to a lesser extent, other fatty acids. Using interactive LC in reverse-phase mode, the oligomers of the surfactant were separated according to their hydrophobicity/hydrophilicity balance. On the other hand, IM spectrometry dispersed the surfactant oligomers by their charge and collision cross section (i.e. size/shape). With either separation method, an increased number of fatty ester groups and/or lack of the polar sorbitan (or isosorbide) core led to higher retention/drift times, enabling the separation of isobaric species or species with superimposed isotope patterns, so that their ester content could be conclusively identified by MS(2). LC-MS and IM-MS permitted the detection of several byproducts besides the major PEO-sorbitan oleate oligomers. LC-MS provides the separation resolution needed for quantitative determination of the degree of esterification. IM-MS, which minimizes analysis time and solvent use, is ideally suitable for a fast, qualitative survey of samples differing in their minor constituents or impurities.
authors.affiliation: Department of Chemistry, The University of Akron, Akron, OH 44325-3601, United States.
authors.forename: Nilüfer
authors.initials: N
authors.lastname: Solak Erdem
authors.affiliation: Department of Chemistry, The University of Akron, Akron, OH 44325-3601, United States.
authors.forename: Nadrah
authors.initials: N
authors.lastname: Alawani
authors.affiliation: Department of Chemistry, The University of Akron, Akron, OH 44325-3601, United States. Electronic address: wesdemiotis@uakron.edu.
authors.forename: Chrys
authors.initials: C
authors.lastname: Wesdemiotis
keywords: Ion mobility separation; Isobar differentiation; Nonionic surfactants; Polysorbate 85; Reverse-phase chromatography; Tandem mass spectrometry