The effect of ionic liquid (IL) coating on the electrochemical properties of preoxidized Cu 3 (PO 4 ) 2 (ox-Cu 3 (PO 4 ) 2 ) electrodes was explored in pH-varied Na 2 HPO 4 solutions. The IL of N-propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PMPy-TFSI) was found to stabilize the redox properties of ox-Cu 3 (PO 4 ) 2 electrodes in weakly acid and alkaline solutions. Furthermore, the amperometric response of the PMPy-TFSI/ox-Cu 3 (PO 4 ) 2 electrodes presented good linearity in the range of 91-500 μM for most α-amino acids (AAs). The PMPy-TFSI/ox-Cu 3 (PO 4 ) 2 electrodes are equipped with a high performance liquid chromatography system to perform the good selectively and specific detection of AAs. The PMPy-TFSI coating shows promise for the wider application of ox-Cu 3 (PO 4 ) 2 electrodes in acidic and alkaline solutions for the detection of electroactive and nonelectroacitve AAs.