Selective Spectrophotometric Determination of Gallium(III) with 2-(5-Bromo-2-Pyridylazo)-5- Diethylaminophenol in the Presence of Sodium Dodecylsulfate and BRIJ 35

For a selective spectrophotometric determination of gallium(III) without interference of aluminium(III), firstly, the color developments between gallium(III) and various chelating azo-dyes; 4(2-pyridylazo) resorcinol (PAR), 2-(5bromo-2-pyridylazo)-5-diethylaminophenol (5-Br.PADAP) in the presence or absence of surfactant alone; cationic-, anionic-, nonionic-surfactants or surfactant combination; cationic-nonionic-, anionic-nonionic-, cationic-anionic mixed surfactants, were systematically investigated. From these color developments, 5-Br.PADAP in tested azo-dyes, and surfactant-combination of sodium dodecylsulfate (SDS) as an anionic surfactant and Brij 35 ((polyoxyethylene)dodecylether) as a nonionic surfactant was selected for a selective assay of gallium(III) in the coexistence of aluminum(III). The calibration graph was linear in the range of 0-9.0 μg/10 ml gallium(III) by measuring the absorbance at 575 nm of 5-Br.PADAP-gallium(III) color development in the coexistence of SDS and Brij 35, and molar absorptivity was 1.2 x 10 5 1 mol −1 cm −1 . The proposed method showed a sufficient selectivity in comparison with other spectrophotometric methods using a chelating azo-dye alone without surfactant; it was scarcely affected by coexisting-aluminum(III). The application to artificial waste water containing gallium(III), aluminum(III), iron(III), etc, was relatively satisfactory; recovery test, 99.1 - 101.1%.