Study on the retention behaviour of metal-tetraphenyl porphine chelates in reversed-phase high performance liquid chromatography

The retention behaviour of metal chelates of alpha,beta,gamma,delta-tetraphenylporphine (TPP) was studied in reversed-phase high performance liquid chromatography (RP-HPLC). On C18 column, with various organic solvents as mobile phases, the retention of the chelates tends to increase in the following order: ZnTPPTPPNiTPPCuTPP. This retention behaviour can get a good explanation from Horvath's "solvophobic theory". With the assumption that the electrostatic field strength of metal chelates can be measured by the ratio of electronegativity vs. ionic radius (EN/ri) of central metal ion, EN/ri was established to be an index for the retention behaviour of metal-TPP chelates. It was found that lnk' is in good linear relationship with the EN/ri value.