Solid-phase extraction of metal ions and their estimation in vitamins, steel and milk using 3-hydroxy-2-methyl-1,4-naphthoquinone-immobilized silica gel

3-Hydroxy-2-methyl-1,4-naphthoquinone-immobilized silica gel has been used for the adsorption and estimation of copper, cobalt, iron and zinc by both batch and column techniques. The distribution coefficient D determined for each metal ion was as follows (ml g(-1)): Fe, 3.6 x 10(2); Cu, 3.9 x 10(2); Co, 3.8 x 10(2); Zn, 4.1 x 10(2). Methods have been developed to estimate zinc, copper and cobalt in milk, steel and vitamin samples respectively.