Spectrophotometric determination of uranium in natural water with the new chromogenic reagent p-carboxychlorophosphonazo

The synthesis and purification of p-carboxychlorophosphonazo (CPApK) are described. In acidic medium, uranium forms a sensitive β-type complex with CPApK (ε = 1.78 × 105 l mol−1 cm−1 at 714 nm). In the presence of polyvinyl alcohol (PVA), the molar absorptivity increases further (ε = 2.72 × 105 l mol−1 cm−1). Beerʹs law is obeyed for 4–12 μg of uranium in 25 ml of solution. A method has been satisfactorily developed for the Spectrophotometric determination of uranium in seawater and lake water with a prior adsorption and desorption.