Spectrophotometric Determination of Cobalt (II) Using 4-(6-Bromo 2-benzothiazolylazo) Orcinol as an Organic Reagent

Abstract

A sensitive, simple and selective spectrophotometric method was proposed for the rapid
determination of cobalt(II) using 4-(6-Bromo 2-benzothiazolylazo) Orcinol(6-BrBTAO).
Alcoholic solution of 6-BrBTAO form a 1:2 pink complex with cobalt(II) ions at pH ranges 5.0-
10.0, absorbing maximum at 514 nm. The molar absorptivity and the Sandell’s sensitivity of the
complex are 2.574x103L mol-1cm-1 and 0.022μg.cm-2 respectively. . Under the optimum
established conditions, which led to a detection limit of 0.51 μg.mL-1 of Co (II) and concentration
range of 0.7-30 μg.mL-1 with percent recovery of 100.43±1.23. The precision for seven replicate
measurements of 15 μg.mL-1 Co(II) was of 1.7%. The method was applied to the determination
of cobalt in some vegetables samples such as radish, carrot and spinach with satisfactory results.