Improved spectrophotometric method for determination of galliurn(III) with Zincon

Abstract

Improved spectrophotometric method for determination of gallium with Zincon in the presence of Tween 20(polyoxyethylene sorbitanmonolaurate, LT-20), as a nonionic surfactant, in a weakly acidic solution has been proposed. The absorption maximum of the Zincon-gallium complex in the presence of 0.2% Tween 20 is at 640 nm against water. The absorbances of the gallium complex and Zincon are stable and constant in the pH range of 3.4 to 4.1. The Beer's law is obeyed up to 35 μg of gallium in final volume of 10 ml at 640 nm. The apparent molar absorptivity is 2.44 × 10⁴ dm³ mol^-1 cm^-1 with Sandell sensitivity of 0.0029 μg/cm². The relative standard deviation is 1.1 % for 17.5 μg of gallium(n=6). Aluminum, zinc, calcium, thiosulfate ions did not interfere. The molar ratio of Zincon to gallium is estimated to be 1.5 : 1 in the presence of Tween 20 by continuous variation, mole ratio, and equilibrium concentration methods.