Characterization of Complex Polysorbate Formulations by Means of Shape-Selective Mass Spectrometry

Abstract

Complex synthetic formulations based on polysorbates can be challenging to characterize. They may be composed of many similar products including those of the same molecular weight, which cannot be readily separated by separation science approaches. Carbon number variation and ethylene oxide distribution add to the complexity. The properties of these formulations will be dependent on the chemical structure and relative concentration of formulation components. Here we describe the use of two experimental approaches based on mass spectrometry to provide enhanced characterization of these formulations. The first utilizes an atmospheric pressure solids analysis probe to rapidly determine the percentage content of individual esters in a formulation. These are shown to be in good agreement with product specification sheets. In a second approach, mobility separation has been integrated into a MALDI-MS/MS experiment to categorize major, minor, and trace ingredients. Components of identical molecular mass in the polysorbate formulations have been separated by ion mobility and then fragmented for additional characterization. The rapidity and level of structural detail provided by these experiments offers a significant opportunity to develop practical screening methods for complex formulations.

Molecular characterization of nonionic surfactant components of the Corexit® 9500 oil spill dispersant by high‐resolution mass spectrometry

“…The resolving power needed to differentiate isobars is dependent on the m/z values of the features of interest and the mass separation. Previous polysorbate methods relied on MALDI‐IM‐MS to separate isobaric compounds by size and shape; however, in our work, it was also possible to use LC/HRMS to separate close eluting, isobaric compounds.…”

“…Polysorbate species have been previously characterized by various methods including matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight (TOF) mass spectrometry (MS), liquid chromatography (LC)/MS, ion mobility (IM)‐MS, and by charged aerosol detection . Ayorinde et al used MALDI‐MS to identify nonesterified, monooleate, and dioleate homologue series in PS 80; however, the method was unable to distinguish structural isomers.…”

Scientific Opinion on the re‐evaluation of polyoxyethylene sorbitan monolaurate (E 432), polyoxyethylene sorbitan monooleate (E 433), polyoxyethylene sorbitan monopalmitate (E 434), polyoxyethylene sorbitan monostearate (E 435) and polyoxyethylene sorbitan tristearate (E 436) as food additives

“…Furthermore, polysorbate formulations were analysed using two-dimensional liquid chromatography (Abrar and Trathnigg, 2010), matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (Ayorinde et al, 2000) after hydrolysis and silylation by gas chromatography (Brueschweiler and Hautfenne, 1990), high-performance liquid chromatography (HPLC) of the free lauric acid after hydrolysis (Öszi and Pethö, 1998), HPLC with an ammonium cobalt thiocyanate complexation column (McKean et al, 1987), an automated fluorescence polarisation assay (Wenger et al, 2005) and shape selective mass spectrometry (Snelling et al, 2012). …”

Multidimensional Mass Spectrometry of Synthetic Polymers and Advanced Materials

“…Monitoring the fatty acid losses from ethoxylated surfactant cations is particularly useful for oleates, as the unit added upon oleate formation, C 18 H 32 O, is isobaric with (C 2 H 4 O) 6 . In this case, the degree of esterification can be simply determined from the number of oleic acid losses observed in the MS 2 spectra…”