An on-plate specific enrichment method is presented for the direct analysis of peptides phosphorylation. An array of sintered TiO2 nanoparticle spots was prepared on a stainless steel plate to provide porous substrate with a very large specific surface and durable functions. These spots were used to selectively capture phosphorylated peptides from peptide mixtures, and the immobilized phosphopeptides could then be analyzed directly by MALDI MS after washing away the nonphos- phorylated peptides.