Spectroscopic studies of the interaction between Chromium Nitrate complex of the ligand, 3,4,5,13,14,15- hexamethyl-2,6,12,16,21,22-hexaazatricyclo [15.3. I1-17 I7-11]dicosa-1 (21),2,5,7,9,11(22),12,15,17,19-decaene shown in [figure 1] showed a selective interaction between complex and monohydrogen phosphate anion respect to the other anions tested. The sensor worked well with a wide working concentration of 1.0x10-1 M – 4.0x10-7 M, detection limit of 2x10-7 M and a Nernstian slope of -28.6±0.3 mV per decade. The electrode had relatively short response time, less than 15s.