Incorporation of Capillary-Channeled Polymer (C-CP) Fibers Into Micropipette Tips For Solid Phase Extraction With Applications in Bioanalysis

Solid phase extraction (SPE), is a widely used sample preparation method that is currently experiencing a surge in research interest, clever architecture/format development, and stationary phase characterization.1-3 SPE devices commonly exist in syringe, cartridge, disk, and micropipette tip formats.4 Micropipette tip SPE has enhanced the determination of proteins by electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) by handling micro-liter volumes of sample and buffer removal/solvent exchange.5-7 Buffers have deleterious effects on ionization taking place in MS sources due to preferential ionization, ion suppression effects, and the formation of adduct species competing for ionization in MS.8 Using micropipette tip SPE, proteins can be selectively extracted from biological buffers and exchanged into a solvent more conducive to MS; thereby improving signal and sensitivity. Capillary channel polymer (C-CP) fibers have been used for reversed phase separations of proteins with a number of positive attributes realized.9 The highly efficient fluid transport, low material cost, wide range of chemical diversity, and robust fiber materials make the C-CP fibers excellent candidates for various separation formats. Presented here is the introduction of polypropylene (PP) and polyester (PET) C-CP fibers as a stationary/support phases for the SPE of proteins from defined buffered solutions prior to ESI-MS10 and MALDI-MS analysis. Using two benchmark proteins, lysozyme in phosphate buffered saline (PBS) and myoglobin in tris buffer, it was demonstrated by ESI-MS and MALDI-MS that PP C-CP fiber-extracted protein samples exhibited more efficient protein ionization, higher signal-to-noise ratios, and more precise molecular weight determinations when compared to buffered protein samples of the same concentration. The extraction efficiencies of PET and PP fibers have been compared for both lysozyme and bovine serum albumin from PBS. Quantitative as well as qualitative data obtained using ESI-MS, MALDI-MS, and UV-VIS demonstrates the capabilities of C-CP fibers as SPE sorbents in bioanalysis