Determination of stability constants of Cu(II), Co(II), Zn(II), Ni(II) andMn(II) chelates with 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,27-tetrapropionic acid by reversed-phase high performance liquid chromatography

The stability constants (K-ML) 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-tetrap ropionic acid, or coproporphyrin-I (CPI) have been determined by reversed-p hase high performance liquid chromatography (RP-HPLC) on a octadecyl-blonde d silica gel (C-18 silica) with developing solvent (69:31 v/v) methanol-buf fer at pH 7 (buffer ionic strength 0.270 mol L-1: 0.018 mol L-1 boric, phos phoric 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 K-ML were 6.02 +/- 0.26 for the Cu(II), 5.37 +/- 018 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).