Preparation of a TiO2 nanoparticle-deposited capillary column by liquid phase deposition and its application in phosphopeptide analysis.

Analysis of phosphopeptides from complex mixtures derived from proteolytic digestion of biological samples is a challenging yet highly important task. Since phosphopeptides are usually present in small amounts, enrichment is often necessary prior to their characterization by mass spectrometry. In this study, a thin layer of titanium dioxide (TiO2) nanoparticles (NPs) was deposited onto the surface of capillary column by liquid phase deposition (LPD) technique and applied to selectively concentrate phosphopeptides from protein digest products. This is, to our knowledge, the first demonstration of using liquid phase deposition to construct in-tube solid phase microextraction devices for biological analysis. By coupling the device off-line or on-line with mass spectrometry analysis, experiments for systematic optimization of loading and washing conditions were carried out, and good trapping selectivity of TiO2 NP-deposited capillary columns towards phosphopeptides was demonstrated.