Detection of mercury ions (Hg2+) in urine using a terbium chelate fluorescent probe

A novel, highly sensitive and specific detection method of Hg2+ based on the fluorescence quenching of a terbium chelate probe was presented. The terbium chelate probe is comprised of a quinolone-based dye molecule (cs124) as the light-absorption antenna and a polyaminocarboxylate-based chelator (DTPA) strongly binding metal and lanthanide ions. The cs124–DTPA–Tb is highly luminescent in aqueous solution. The aqueous Hg2+ can efficiently quench the fluorescence of cs124–DTPA–Tb. The fluorescent intensity of cs124–DTPA–Tb displayed a good linear response to Hg2+ concentrations in the range of 4–600 nM with a detection limit of 4 nM. This method was applied successfully to determine the levels of Hg2+ in urine. The quenching mechanism of cs124–DTPA–Tb by Hg2+ is discussed. Compared with other fluorescent assays for Hg2+, a terbium chelate probe has an advantage that the interference of short-lived background fluorescence from sample can be eliminated efficiently by a determination in the mode of time-resolved fluorescence. This method could be used to detect the trace Hg2+ in biological samples and environmental water.