Structural characterization of silicone polymers using compositional ultra-high performance liquid chromatography separation, electrospray ionization, and high resolution/accurate mass

• High resolution reverse-phase UHPLC separation of silicone polymers combined with high resolution/accurate mass ESI MS.
• High information content LC-MS screening methodology for a broad range of silicone polymer end-group polarity.
• Demonstration of capability for raw material characterization, as well as comparative analysis, showing the separation of isomeric oligomers.

In this article, the development of an on-line ultra-high performance liquid chromatography (UHPLC)-high resolution/accurate mass (HR/AM) methodology for timely characterization of a broad range of silicone polymers is described. Electrospray ionization was optimized for silicone polymers to enable the direct coupling of the separation with mass spectrometry. Reverse-phase UHPLC was optimized to provide a high resolution separation of oligomers by molar mass and by end-group composition. With the high resolution compositional separation, multiple pseudo-molecular ion species were indexed with retention time and assisted in rapid identification of oligomer species. Relative retention times of different oligomer end-group species separated based on polarity provided additional information to aid data interpretation. These additional pieces of information were combined with accurate mass to provide a high information content analysis in a relatively short time frame. This methodology was applied to polymer end-group characterization, as well as comparative analysis examples.

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