Extraction and characterization of organic ligands from oceanic water columns by immobilized metal ion affinity chromatography

Organic ligands for Cu(II) were extracted from oceanic water columns by immobilized metal ion affinity chromatography (IMAC). Separation of organic ligands from bulk dissolved organic matter (DOM) allowed the chemical characterization of organic ligands. Measurements of complexing abilities, as well as fluorescence and chemical analyses, indicated that natural ligands were a mixture of, at least, two different types of organic ligand. One type was prominent in the surface water, it was weakly fluorescent but rich in both primary amines and carbohydrates. The other type was predominant in deep water and had the converse characteristics, namely, low levels of both primary amines and carbohydrates, but relatively strong fluorescence. The measurements of the complexing ability of organic ligands from the surface waters suggested the existence of a natural ligand (log K′CuL ≈ 9) that has one or two primary amines as copper-binding sites.