Membrane optode for uranium(vi) preconcentration and colorimetric determination in real samples

Abstract

A membrane optode formed by physical inclusion of a chromophore, 2-(2-benzothiazolylazo)phenol (BTAP), and uranium(VI) anions into a plasticized cellulose triacetate (CTA) matrix was illustrated for preconcentration and colorimetric determination of U(VI) from aqueous samples. The optode was examined for uranium uptake in bicarbonate/carbonate medium (∼160 ng mL⁻¹) at pH 6.5–7.0 in the presence of triethanolamine buffer (TEA). The inclusion of an anion-exchanger, dinonylnapthenic sulphonic acid (DNNS), was found to be necessary for the formation of a U(VI)–BTAP complex in the optode matrix, resulting in a distinct color change of the optode from orange to pink after uranium sorption. The composition of the optode was optimized by varying the amounts of different plasticizers and DNNS to obtain the minimum response time towards U(VI) in aqueous bicarbonate medium. The effects of different experimental parameters involved in the detection and quantification of U(VI) using the optode were optimized. The optode analytical performance was evaluated in terms of interference of cations and anions, reusability, equilibration time, detection limit, etc. and compared with the conventional spectrophotometric method for U(VI) using different chromophores. The optode developed in the present study was tested in real samples with good results compared to the graphite furnace atomic absorption spectroscopy (GF AAS) method.