Metal-organic complexes in seawater — An investigation of naturally occurring complexes of Cu, Zn, Fe, Mg, Ni, Cr, Mn and Cd using high-performance liquid chromatography with atomic fluorescence detection

Abstract

Metal-organic complexes were isolated from coastal seawater by adsorption onto octadecyl-bonded silica (SEP-PAK cartridges) and injected into a high-performance liquid chromatograph. Trace metals were identified in the eluate by a four-channel non-dispersive atomic fluorescence detector. Organic complexes of copper, zinc, iron, magnesium, nickel and manganese were found to be present but no complexes of chromium or cadmium were detected. The complexes covered a wide range of polarities with no specific complexes being predominant. Interference from the stainless-steel chromatograph was negligible. The technique provides a minimum estimate of the amount of metal organics and it is suggested that a significant fraction of the metal organics present are too polar to be completely retained by the SEP-PAK cartridges. Typical values of the amounts of trace metal isolated by this technique corresponded to concentrations in the original seawater of >65 ngl −1 (Cu), >27 ngl −1 (Fe) and >41 ngl −1 (Zn).