A Highly Sensitive Colour Reaction of Gallium (Ga(III)-BPR-Tween80-CTAB System)

A highly sensitive method for the spectrophotometric determination of gallium with bromopyrogallol red (BPR) in the presence of Tween80 and cetyltrimethylammon-ium bromide (CTAB) has been developed. In a medium of monochloroacetic acid (pH 2.87-3.42), Ga(Ⅲ) forms red-purple complex with the above reagents. The complex exhibits maximum absorption at 528 nm. The molar absorptivity is 5.72×l05 I·mol-1· cm-1 (in the presence of high concentration of Tween80(0 .8%))and 1.09× 106 I·mol-1· cm-1 (in the presence of low concentration of Tween80 (0.24%) and 4.8×10-5% H2O2). Beer's law is obeyed for Ga(Ⅲ) in the range of 0 .1-1.0μg/25 ml. The effects of diverse ions on the determination of Ga(Ⅲ) are examined. After extraction of Ga (Ⅲ) into n-butyl acetate from 6 mol/l HCl, the method has been used for determination of Ga(Ⅲ) in zeolite catalyst with satisfactory results.