Aminopropyl-silica gel modified with nickel(II)-phthalocyanine for separation of π-electron rich compounds by high performance liquid chromatography

Aminopropyl-silica gels modified with a nickel(II)-phthalocyanine derivative (Ni-PCS(D)) were evaluated as HPLC-stationary phases for the separation of π-electron rich compounds such as polyaromatic hydrocarbons (PAHs) and mutagens. A column packed with Ni-PCS(D) retains some π-electron rich compounds longer than a column packed with copper(II)-phthalocyanine derivatives (Cu-PCS(D)), suggesting that a π-π electron interaction and an additional interaction between Ni-PCS and the compound. On the basis of the retention data of four-ring PAHs, anthracene derivatives and heterocyclic aromatic hydrocarbons, we propose that the additional interaction would be due to an interference of the π- or n-electrons would interact and with the d-orbital of the Ni atom in Ni-PCS. Further, the Ni-PCS(D) column is expected to be superior to the Cu-PCS(D) column for the separations of drugs, mutagens and pollutants which have both π-electrons and ligand atom(s).