Abstract: With Co/GCion implantation modified electrode as the working electrode, in 0.1mol/L HAc-NaAc (pH= 4.96) buffer solution, a sensitive reductive wave of methotrexate was obtained by linear sweepvoltammetry.The peak potential was -0.95 V(vs.SCE).The peak current was proportional to the con-centration of methotrexate in the range of 2.2 × 10^-7～8.8 × 10^{-6 mol/Lwith the detection limit of 1.1×10-8 mol/L.The behavior of the reduction wave was studied and applied to the determination ofmethotrexate in tablets.The reduction process was irreversible with adsorption, The composition anddepth distribution of elements on the surface of the Co/GCE were determined by Auger electron spec-troscopy and X-ray photoelectron spectroscopy.The experiments showed that Co was surely implanted in-to the surface of glassy carbon.The implanted Co catalyzed the reduction of methotrexate.}

Key words: Methotrexate, Electrochemical behavior, Ion implantation, Modified electrode