Determination of Ultratrace Gallium in River Water by Electrothermal Atomic Absorption Spectrometry after Preconcentration with Solvent Extraction and Back Extraction

Abstract

Abstract A method for the determination of gallium at ng dm−3 levels in river water is described. Gallium is extracted into carbon tetrachloride as an ion pair of gallium–5-sulfo-8-quinolinol (H2QS) chelate anion with tetradecyldimethylbenzylammonium chloride (Zephiramine), and subsequently back-extracted into 0.3 cm3 of a nitric acid solution. The high efficiency of extraction and back extraction allows gallium to be concentrated about 5000-fold with a combined single extraction and back extraction. The back-extracted solution, containing 250 μg cm−3 of nickel as a matrix modifier, is suitable for the determination of gallium by electrothermal atomic absorption spectrometry (ETAAS). The detection limit (3σ) for gallium is 0.29 ng dm−3 based on a 1500-fold preconcentration. The concentration of dissolved gallium in river water was found to be 5.3—9.2 ng dm−3 by the proposed method.