Study of complexation behavior for Cobalt(II) with a new ligand derived from pA benzoic acid to estimate Co2+content in vitB12

The spectrophotometric method was suggested for the determination of trace amounts of cobalt. The method is based on the reaction of cobalt (selected between some ions) with a novel prepared reagent 4-((1-ethoxy-1,3-dioxobutan-2-yl) diazenyl)benzoic acid at pH 9 in the presence of sodium hydroxide as a basic medium to form a distinct color complex that shows maximum absorption at λmax = 421nm. Under specific conditions, Beer’s law is obeyed to control the concentration mode of 10-60 ppm. The molar absorptivity was 106.0695 L.mol-1cm-1, Sandellʹs sensitivity was 2.6×10-5, and the detection coefficient was 0.9984. The method was applied with good results to estimate cobalt in multiple doses of vitamin B12 (tablets and injection), then compared with FAAS instrumental, for which the results were close.