A colorimetric method for simultaneous preconcentration and determination of
uranium(VI)
anions from
aqueous samples was developed using a membrane
optode formed by physical
inclusion of a chromophore 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) into a plasticized
cellulose triacetate matrix. The
optode was tested for
uranium uptake in bicarbonate/
carbonate medium (approximately 10(-4) M) at pH 7-8 in the presence of
triethanolamine buffer. The
inclusion of an anion-exchanger tricaprylylmethyl
ammonium chloride (Aliquat-336) was found to be necessary for the formation of U(VI)-Br-PADAP complex in the
optode matrix, resulting into distinct color change of the
optode from
yellow to magenta after
uranium sorption. The composition of the
optode was optimized by varying the amounts of different
plasticizers and Aliquat-336 to obtain minimum response time towards U(VI) in
aqueous bicarbonate medium. The proportionality in
intensity of the magenta color of the
optode samples loaded with varying amounts of U(VI) suggested its potential applications for screening of U(VI) in
aqueous samples by
visual colorimetry. The effects of experimental parameters involved in the detection and quantification of U(VI) using
optode were optimized. The
optode analytical performance was evaluated in terms of interference of
cations and
anions, equilibration time, reusability, detection limit, etc. and compared with the conventional
spectrophotometric method for U(VI) using same chromophore Br-PADAP. The
optode developed in the present work was tested in real alkaline Mg(NO(3))(2) effluent sample obtained from
uranium extraction process.
