DETERMINATION OF STABILITY CONSTANTS OF Cu(II), Co(II), Zn(II), Ni(II) AND Mn(II) CHELATES WITH 3,8,13,18-TETRAMETHYL-21H,23H-PORPHINE-2,7,12,17-TETRAPROPIONIC ACID BY REVERSED-PHASE HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

The stability constants (KML) of Cu(II), Co(II), Zn(II), Ni(II), and Mn(II) chelates with 3, 8, 13, 18 -tetrametyl-21H, 23H-porphine -2,7,12,17- tetrapropionic acid, or coproporphyrin-I (CPI) have been determined by reversed-phase high performance liquid chromatography (RP-HPLC) on a octadecyl-bonded silica gel (C18 silica) with developing solvent (69:31 v/v) methanol-buffer at pH 7 (buffer ionic strength 0.270 mol L−1: 0.018 mol L−1 boric, phosphoric and acetic acid, and 0.036 mol L−1 sodium hydroxide), and 0.050 mol L−1 of NaCl, with UV detection. The values of log KML were 6.02±0.26 for the Cu(II), 5.37±0.18 for the Co(II), 4.51± 0.21 for the Zn(II), 4.52± 0.21 for the Ni(II) and 6.38± 0.04 for the Mn(II).