Simplification of electrospray mass spectra of Polysorbate 80 via cation transfer to carborane anions.

Mass spectrometric analysis of polymer mixtures via electrospray ionization can be complicated due the presence of multiple ion types, multiple charge states and multiple oligomeric distributions that complicate the detection and identification of mixture components. Polysorbate 80 (commercially known as Tween(®) 80) provides an example of this type, where the presence of polyoxyethylene sorbitan monooleate (PSO) byproducts gives rise to overlapping polymer distributions. It is desirable to simplify the spectrum in order to identify each component of what is inherently a complex mixture of fatty esters bound to different head groups. In this work, we show that gas-phase ion/ion reactions with carborane anions allow for the charge reduction of Tween(®) 80 peaks by selectively removing metal adducts bound to the synthetic polymer. The resulting singly charged spectrum reduces overlapping distributions and thus simplifies the identification of the components found in a Tween(®) 80 sample. The overall approach described here would likely lead to similar benefits in the analysis of other polymers that tend to ionize via metal ion adduction.