Detection of Hg²⁺ in water environment by fluorescence spectroscopic methods

Inorganic mercury (Hg²⁺) produces toxic effects even at very low concentration. High sensitive fluorescent probes for Hg²⁺ detection has been researched and synthesized. A fluorescence detection system is built for Hg²⁺ detection in water environment with fluorescent probes as the detection reagent. Fiber coupled LED with high brightness is developed and used as excitation light source. And the optimized excitation wavelength is about 520 nm. The measurements of fluorescence spectra is obtained by means of optical fiber spectroscopic techniques. Fluorescence detection experiments are carried out for a range of different concentrations of Hg²⁺ in aqueous solutions. The center wavelength of the fluorescence spectra is about 580 nm which is unchanged in the experiments. Relationship between Hg²⁺ concentrations and the fluorescence intensity is studied. A positive correlation exists between the intensity of fluorescence spectrum and the concentrations of Hg²⁺. The fluorescence intensity grows with increasing the concentration of Hg²⁺ for the same excitation light. When the concentration of Hg²⁺ is high enough, the fluorescence intensity increases slowly. And a numerical model is built for the concentration calculating. The detection limit is 0.005 μmol/L in the experiments. The Hg²⁺ detection system reported has many advantages such as small size, rapid response, high-sensitivity, and can be used for on-site testing of the water quality.