Multiple digestion by the tandem
microreactors showed higher sequence coverage compared with that by in-solution or the single
microreactor. Moreover, the tandem microreactor that was made by using the combination of protease-
immobilized microreactor and phosphatase-immobilized microreactor showed the capability for
phosphorylation site analysis in phosphoproteins without the use of any enrichment strategies or radioisotope
labeling techniques.