Capillary-channeled polymer fibers as a stationary phase for desalting of protein solutions for electrospray ionization mass spectrometry analysis.

Micropipet solid-phase extraction (SPE) tips have been used to desalt and purify proteins and peptides from mixtures of buffers and biological solutions. Removing salts and buffers prior to electrospray ionization mass spectrometry (ESI-MS) characterization improves the detection limits and the sensitivity of the protein analyses. Recently, capillary-channeled polymer (C-CP) fibers have been investigated as stationary phases for high-performance liquid chromatography separations of proteins. Polypropylene C-CP fibers incorporated as sorbent materials in micro-SPE tips are shown to effectively remove both inorganic and organic buffers from proteins in defined solutions. The architecture of the fibers provides large surface areas in comparison to conventional round fibers and is readily packed into capillaries that can be affixed to micropipet tips. Desalting of protein solutions is demonstrated for ESI-MS analysis through increased signal-to-noise ratios and reduced spectral complexity.