A Highly Sensitive Spectrophotometric Method for Gallium Determination with Chrome Azurol S in the Presence of Mixed Cationic-Nonionic Surfactants and its Application in Plant Analysis

A simple and very sensitive spectrophotometric method determining microgram quantities of gallium (Ga) has been developed. The method is based on the complex of Ga(III) with Chrome Azurol S (CAS) in the presence of benzyldodecyldimethylammonium bromide (ST) and polyoxyethylenesorbitan monopalmitate (Tween 40). The complex forms in weakly acid solution (pH 3.8) and shows the absorption maximum at 627 nm. The molar absorptivity (ε) of this system is 1.87 × 10⁵ L mol^?1 cm^?1, and it is clearly higher than ε of other spectrophotometric methods of gallium determination. The detection and quantification limits (LOD, LOQ) are 7.6 × 10^–3 and 0.023 µg mL^?1, respectively. Beer^‘s law is obeyed in the range from 0.02 to 0.60 µg mL^?1 of Ga. The precision and accuracy are good. This first spectrophotometric method of Ga(III) determination in the four-component system has been successfully applied for the analysis of mushrooms and grasses with low content of gallium.