The high-pressure liquid chromatographic separation of copper(II) and nickel(II) schiff base chelates on microparticulate silica

The separation of neutral copper and nickel chelates of two representative Schiff base ligands, N,N'-ethylenebis(acetylacetoneimine) and N,N'-ethylene-bis(salicylaldimine) is reported on a column of 10-μm diameter silica. Both pairs of chelates are well resolved with good peak shape and efficiencies when the mobile phase is 4 : 1 methylene chloride—acetonitrile. The u.v. detector response at 254 nm is linear over approximately three orders of magnitude of quantity of chelate injected; the detection limits are in the low nanogram range. Qualitative and quantitative elution of undegraded chelates was demonstrated by u.v. spectrophotometry, mass spectrometry and electron spin resonance spectroscopy.