A　new　approach　was　described　to　achieve　very　sensitive　analysis　of　peptide　hormone　of　brain　and　intestine　by　capillary　electrophoresis　coupled　with　a　transient　isotachophoresis　(tITP)　preconcentration　method.　The　system　used　was　electrospray　ionization　mass　spectrometry　(ESI-MS)　as　detector　and　equipped　with　a　sheath　flow　configuration.　The　effects　of　sample　matrix,　pH　and　concentration　of　leading　electrolyte　(LE),　sample　injection　time,　and　ESI-MS　instrumental　parameters　on　the　efficiency　of　the　sample　stacking　were　investigated　in　detail.　Under　the　optimized　conditions,　lower　than　micromole　(0.01　mu　M)　concentrations　of　the　peptides　were　easily　detected.　Compared　to　traditional　hydrodynamic　injection　methods,　about　40-230-fold　increase　in　detection　sensitivity　was　obtained　by　this　technique.　A　distinguishing　feature　of　the　described　approach　is　that　the　background　electrolyte　can　serve　as　terminating　electrolyte　(TE),　which　simplifies　the　process　of　the　experiments.　The　method　was　further　evaluated　by　the　analysis　of　low　concentration　active　peptide　mixtures　spiked　in　hypothalamus　tissue　of　the　rat.　Copyright　(C)　2008　John　Wiley　&　Sons,　Ltd.