Spectrophotometric determination of vanadium (V) using an organic reagent [4-(6- nitro -2-benzothiazolylazo)pyrogallol]

Abstract

A new chromogenic reagent [ 4-(6-Nitro-2-benzothiazolylazo)pyrogallol] (6-NO2BTAPY), was synthesized by diazo coupling of(2-amino-6-nitro benzothiazol) (2-ANO2BT) with pyrogallol, and used for the spectrophotometric determination of vanadium (V).This method was simple, sensitive, selective and rapid for reaction between V5+ and (6-NO2BTAPY),to form a pink complex having a molar ratio of (1:2) (V-6-NO2BTAPY) at pH 6.0. The molar absorptivity of the complex was 0.2279×104 L.mol-1 cm-1 at  max 490 nm. Beer’s law is obeyed in the range of (0.1–10) ppm of vanadium ,and the stability constant was found to be 3.4 × 108 L2.mol-2. The relative standard deviation for seventh replicate measurements ,recovery ,and relative error values of this method were found to be 2.5712,10.3, and3 respectively . The interference of foreign ions was also investigated. All the other ions studied did not interfere with vanadium determination except for Cr3+ , Cu2+,Co2+,Ni2+, Zn2+ , and pb2+. The interferences were eliminated approximately using suitable masking agent .