LAUSR

In this study, an in‐tube solid‐phase microextraction column packed with mesoporous TiO2 nanoparticles, coupled with MALDI–TOF–MS, was applied to the selective enrichment and detection of phosphopeptides in complex biological samples. The mesoporous TiO2 nanoparticles with high specific surface areas, prepared by a sol–gel and solvothermal method, were injected into the capillary using a slurry packing method with in situ polymerized monolithic segments as frits. Compared with the traditional solid‐phase extraction method, the TiO2‐packed column with an effective length of 1 cm exhibited excellent selectivity (α‐casein/β‐casein/BSA molar ratio of 1:1:100) and sensitivity (10 fmol of a β‐casein enzymatic hydrolysis sample) for the enrichment of phosphopeptides. These performance characteristics make this system suitable for the detection of phosphorylated peptides in practical biosamples, such as nonfat milk.