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

Abstract

Under pH4.0 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 (ΔF, 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.

Keywords: Curcumin; Fluorescence quenching; Micelles; Triton X-100; Uranyl.