A multisyringe flow injection method for the determination of thorium in water samples using spectrophotometric detection

A fast and simple multisyringe flow injection analysis (MSFIA) method for routine determination of thorium in water samples was developed. The methodology was based on the complexation reaction of thorium with arsenazo (III) at pH 2.0. Thorium concentrations were spectrophotometrically detected at 665 nm. Under optimal conditions, Beer’s law was obeyed over the range from 0.2 to 4.5 μg mL−1 thorium, a 3σ detection limit of 0.05 μg mL−1, and a 10σ quantification limit of 0.2 μg mL−1 were obtained. The relative standard deviations (RSD, %) at 0.5, 2.5 and 4.5 μg mL−1 was 2.8, 1.5 and 0.8%, respectively (n = 10). It was found that most of the common metal ions and anions did not interfere with the thorium determination. The proposed method was successfully applied to its analysis in various water samples.