Simultaneous determination of gallium and indium with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in cationic micellar medium using derivative spectrophotometry

A new derivative spectrophotometric method for rapid and selective trace analysis of Ga3+ and ln(3+) and for their simultaneous determination using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenoI in a cationic micellar medium is reported. Molar absorptivity and Sandell's sensitivity of 1:1 Ga3+ and In3+ complexes at their lambda(max) 553 nm and 558 nm are: 7.22 x 104 l mol(-1) cm(-1) and 5.85 x 10(4) l Mol(-1) cm(-1), and 0.96 ng cm(-2) and 1.96 ng cm(-2), respectively. Linearity is observed in the concentration range 0.023 - 0.700 mg ml(-1) for gallium and 0.076 - 1.52 mg ml(-1) for indium; IUPAC detection limit is 0.012 and 0.035 ng ml(-1), respectively. These metal ions interfere with the determination of each other. However, 0.07 - 0.70 mg ml(-1) Ga3+ and 0.115 - 1.150 mug ml(-1) In3+ could be determined simultaneously when present together by the derivative method without any prior separation. The proposed procedures have been successfully applied for the individual and simultaneous determination of gallium and indium in synthetic binary mixtures, standard reference materials and environmental samples.