Liquid chromatographic separation of metal-tetraphenylporphine complexes based on coordination interaction with immobilized neutral ligand in stationary phase

Abstract

Proposed is a novel liquid chromatographic system for metal chelates based on the coordination interaction between the central metal in a complex and immobilized neutral ligand in the stationary phase. For this purpose, a 2-(4-pyridyl)ethyl bonded silica gel (4-PES) column was newly prepared, and cobalt(II)-, nickel(II)-, copper(II)-, and zinc(II)-tetraphenylporphine (TPP) complexes were separated on the 4-PES column as well as on previously prepared 4,5-dihydroimidazolyl bonded silica gel, 2-(2-pyridyl)ethyl bonded silica gel and a commercial aminopropyl bonded silica gel, packed columns in the normal phase mode. Among them, the strongest retention for the metal-TPP complexes which are considered to be coordinatively unsaturated, was observed on the 4-PES column, indicating that the separation of the metal-TPPs on these columns may mainly be based on the proposed mechanism.