A fluorescent probe for the selective detection of sulfate ions in water

A nicotinamide-anthracene conjugate based fluorescent probe 1 exhibits highly selective fluorescence enhancement at 535 nm only with sulfate in HEPES buffer-DMSO (9 : 1) at pH 7.4. The other anions viz. F-, Cl-, Br-, I-, AcO-, HSO4-, H2PO4-, CN-, OH-, NO3-, ClO4-, SCN-, even if present in excess, do not interfere in the estimation of sulfate. The limit of detection for sulfate ions by probe 1 is 0.5 mu M. Probe 1 can also be used to determine the sulfate ions in tap water using EDTA as a metal ion masking agent. Titration experiments and Job's plot reveal the formation of a 1 : 1 stoichiometric complex between the probe 1 and sulfate ions and DFT studies show the electron transfer from SO42- to anthracene moiety responsible for the observed optical changes.