Determination of dissolved nickel in natural waters using a rapid microplate fluorescence assay method

A new microplate analytical procedure is described for the determination of nickel (Ni²⁺) ions in natural water samples. A lophine analogue fluorescent sensor was synthesized and a spectral study showed a selective fluorescence quenching effect of chemical sensor by Ni²⁺ under optimized conditions. Density functional theory (DFT) calculations confirmed the formation of a Ni(II)L₃ complex obtained by the Job plot. The calculations showed that the fluorescence emission peak of L collapses due to the distortion of L in the complex. The simple and fast microplate procedure allowed us to quantify Ni²⁺ with a linear response from 1.6 to 40 µg L^-1 and a quantification limit of 5.4 µg L^-1 without the need of a preconcentration step. The optimized procedure using high-throughput microplate assay has been applied for the determination of Ni²⁺ in natural water samples with good analytical performances.