Selective Second Order Derivative Spectrophotometric Method for the Determination of Gallium(III) in Presence of Large Excess of Indium(III)

Abstract

A simple, sensitive, and selective second order derivative spectrophotometric method is proposed for the determination of microgram quantities of gallium(III) especially in presence of large excess of indium(III). Ga(III) reacts with 2‐hydroxy‐3‐methoxy benzaldehyde isonicotinoylhydrazone (HMBAINH) chromogene forming an intense greenish yellow coloured soluble complex in acidic buffers and in presence of 0.2% of triton X‐100. The complex showed maximum absorption at 405 nm and at pH 5.0, where the reagent has negligible absorbance. A second order derivative spectrum of the complex solution showed maximum derivative amplitude at 415 nm and again at 460 nm with a zero cross at 442 nm. Beer's law was obeyed in the concentration range 0.036–1.533 µg/ml and 0.070–1.533 µg/ml of Ga(III) at 415 nm and 460 nm, respectively. However, at 404 nm In(III)‐HMBAINH complex showed zero amplitude in the second order derivative spectrum where Ga(III)‐HMBAINH obeyed Beer's law in the range of 0.070–1.394 µg/ml. This allows determination of Ga(III) in presence of large excess of In(III) by second order derivative spectrophotometry. The tolerance limits of other diverse ions and other analytical parameters were also evaluated. The method was applied for the determination of gallium in some synthetic mixtures containing indium.