Selective spectrophotometric determination of cobalt(II) in synthetic mixtures and pharmaceutical formulates with 5-[o-carboxyphenylazo]2,4-dihydroxybenzoic acid
As. Amin et al., Selective spectrophotometric determination of cobalt(II) in synthetic mixtures and pharmaceutical formulates with 5-[o-carboxyphenylazo]2,4-dihydroxybenzoic acid, ANAL LETTER, 34(5), 2001, pp. 749-759
The present work describes a selective, rapid and economical method for the
determination of cobalt(II) using 5-[o-carboxyphenylazo] 2,4-dihydroxybenz
oic acid [CPDB] as a spectrophotometric reagent without heating or extracti
on. The CPDB reacts with Co(II) in presence of Tween 80 surfactant forming
a pink complex of a stoichiometric ratio 1:2 absorbed maximally at 555 nm w
ith stability constant amounting to 10.33. Beer's law is obeyed for a conce
ntration of at least 3.50 mug ml(-1) with Sandell sensitivity of 3.6 ng cm(
-2) and molar absorptivity of 1.64 x 10(4) 1 mol(-1)cm(-1). The relative st
andard deviation for six replicate sample of 2.0 mug ml(-1) is 1.11%. A sel
ective procedure is proposed for cobalt deter mination in presence of diffe
rent metal ions in synthetic mixtures and in pharmaceutical formulations wi
th more accurate results.