Selective colorimetric and fluorescent quenching determination of uranyl ion via its complexation with curcumin

Under pH   4.0 HAc–NaAc buffer medium, curcumin alone possesses extraordinary weak fluorescence emission . Nevertheless, the introduction of Triton X–100 micelles can largely enhance the fluorescence intensity of curcumin . Uranyl ions can complex with micelles–capped curcumin , along with the slight red shift of curcumin fluorescence (about 1–7   nm), a clear decrement of absorbance (424   nm) and fluorescence (507   nm) intensities, and a distinct color change from bright yellow to orange. The fluorescence decrements ( Δ F, 507   nm) are positively correlated to the amount of uranyl ions in the concentration range of 3.7   ×   10 −   6 –1.4   ×   10 −   5   mol   L −   1 . The detection limit of this fluorescence quenching methods is 3.7   ×   10 −   6   mol   L −   1 , which is nearly 9000 times lower than the maximum allowable level in drinking water proposed by World Health Organization. Good selectivity is achieved because of a majority of co–existing substances (such as Ce 4   + , La 3   + , and Th 4   + ) do not affect the detection. The content of uranyl ions in tap water samples was determined by the proposed method with satisfactory results.