Polyglycerol intermediates have been characterized by liquid chromatography-mass spectrometry (LC-MS) with electrospray ionization (ESI). Linear and cyclic components from n = 2-23 in a sample of decaglycerol, for example, have been resolved in the second dimension or mass axis. Molecular weight (MW) distributions for tri-, hexa-, and decaglycerol products have been analyzed as a function of cone voltage and adduct ion (H + , Li + , Na + , K + , Rb + , Cs + , and NH 4 + ). A different combination is required to obtain a reliable MW distribution for each polyglycerol intermediate. The best distribution obtained by ESI/MS is determined by comparing the calculated hydroxyl number and cyclic content to that obtained by wet chemistry and gas chromatography, respectively. Once ESI/MS conditions are established, the distribution can be used, for the first time in polyglycerol analysis, to calculate important parameters such as number average MW, weight average MW, polydispersity, % cyclics, hydroxyl number, wt% above n = 6, etc.Polyglycerols are intermediates for polyglycerol fatty esters, used as additives in the food and personal-care industries. Knowledge of the polyglycerol distribution will help relate composition to performance, optimize process chemistry, and produce newly tailored products. Gas chromatography (GC) of an acetylated polyglycerol can resolve linear and cyclic components only up to hexad chains (1). Furthermore, the peak intensities in the gas chromatogram are progressively attenuated with increasing degree of polymerization. Highperformance liquid-chromatography (HPLC) with refractive index (RI) detection and a carbohydrate column partially resolves polymers up to n = 12, but cyclic and linear components (larger than diglycerol) are not resolved (2). Supercritical fluid chromatography of silanized polyglycerols shows peak maxima up to n = 10. Higher molecular weight (MW) polymers elute, but still not all cyclic and linear components are resolved (3). Liquid chromatography-mass spectrometry (LC-MS) with electrospray ionization (ESI) has advantages compared with all the above techniques since all components FIG. 1. (A) General structure for polyglycerol. (B) Structures for linear and branched diglycerol. (C) Possible structures for monocyclic diglycerol.
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