Optimized and validated spectrophotometric methods for the determination of trace amounts of uranium and thorium using 4-chloro-N-(2,6-dimethylphenyl)-2-hydroxy-5-sulfamoylbenzamide

A facile, rapid and sensitive spectrophotometric method for the determination of trace amounts of UO2(II) and Th(IV) ions in aqueous samples was performed, based on complexation reaction between metal ion and 4-chloro-N-(2,6-dimethylphenyl)-2-hydroxy-5-sulfamoylbenzamide (xipamide). The important analytical parameters and their effects on the reported system were investigated. UO2(II) and Th(IV) react with xipamide in the ratio 1:1 and 1:2 (metal:ligand) in the pH range 7 and 8 to form a complex with an absorption maximum 445 and 325 nm, respectively. The reaction was extremely rapid at room temperature, and the absorbance value remains unchanged for at least 24 h. The apparent stability constants (log βn) and the free energies change (ΔG*) of formation of the complexes were calculated using the results of mole ratio and continuous variation methods. Beerʹs law was obeyed in range 0.2–3.6 μg/mL for UO2(II) and 0.1–4.8 μg/mL for Th(IV). For more accurate analysis, Ringbom optimum concentration range was found from 0.3–3.4 μg/mL for UO2(II) and 0.2–4.2 μg/mL for Th(IV). The apparent molar absorptivity, Sandell sensitivity, detection and quantification limits were also calculated. The interference effect of some anions and cations was also tested. The method was applied to the determination of UO2(II) and Th(IV) in water samples.