Spectrophotometric Determination of Cobalt(II) with Mordant Blue 9 -Application to Vitamin B12 (Injections and Powder)

A spectrophotometric method has been developed for determination of cobalt with Mordant Blue 9 in presence of cetyltrimethylammonium bromide (CTAB) in order to form an intense violet-colored chelate which exhibits maximum absorption at 586 nm at pH 3. Beers law is obeyed over the range of 0.004 -1 ppm with a molar absorptivity 3.97104 l.mol-1.cm-1, Sandells sensitivity index of 1.484 ng.cm-2, while LOD (limit of dedication), LOQ (limit of quantitation) are found to be 4.006 ng/ml (n=10) and 13.353 ng/ml (n=10), respectively. The method has been applied for determination of Co(II) in pharmaceutical preparations.