Essential serum trace metals: II. Determination of copper and zinc

Several complexing ligands for copper and zinc were tested for their feasibility as analytical reagents. Of these, tetraethylthiuram disulfide and its analog, bis (1-piperi-dylthiocarbonyl) disulfide were selected for copper with some advantages determined to accrue to each. Two others, 1-(2-pyridylazo)-2-naphthol and 1-[(5-chloro-2-pyridyl) azo]-2-naphthol were selected for zinc with the preference given to the former for stability of color formed and accessibility of the reagent although the chloro analog is inherently the more sensitive of the two reagents. For those who do not have atomic absorption spectrophotometry at their disposal, the molecular absorption approach still appears to be an excellent one with good selectivity for the two metals described.