Sub-ppb mercury detection in real environmental samples with an improved rhodamine-based detection system

A new procedure is described for the determination of Hg²⁺ ions in water samples. A Rhodamine based fluorescent sensor was synthesized and the experimental conditions were specifically optimized for application to environmental samples, which requires low detection limits and high selectivity in competitive experiments with realistic concentrations of other metal ions. Incorporation of a Rhodamine-6G fluorophore to a previously described sensor and optimization of the buffer system (detection with acetic acid at pH 5.25) enabled significant enhancement of the sensitivity (detection limit = 0.27 μg L^-1) and selectivity. The optimized procedure using high-throughput microplates has been applied to tap and river waters with good results.