This paper describes that the glassy carbon electrode (GCE) modified with a polymer film of non-peripheral amine substituted nickel(II) phthalocyanine (p-4 alpha-Ni(II)TAPc) can be used for the selective and stable determination of guanosine 5'-monophosphate (GMP) in phosphate buffer (pH 4) solution. Bare GCE oxidizes GMP at 1.26 V whereas p-4 alpha-Ni(II)TAPc modified GCE oxidizes it at 1.19 V with enhanced oxidation current. Further, the polymer modified electrode selectively determines GMP in the presence of 400-fold higher concentration of guanine. In differential pulse voltammetry measurements, the current response of GMP was linearly increased with the concentration range of 0.005-1 mM. The experimental detection limit was found to be 5 x 10(-6) M. (c) 2013 Elsevier Ltd. All rights reserved.