Synthesis and properties of arsenic(III)-reactive coumarin-appended benzothiazolines: a new approach for inorganic arsenic detection.

The EPA has established a maximum contaminant level (MCL) of 10 ppb for arsenic (As) in drinking water requiring sensitive and selective detection methodologies. To tackle this challenge, we have been active in constructing small molecules that react specifically with As3+ to furnish a new fluorescent species (termed a chemodosimeter). We report in this contribution, the synthesis and spectroscopy of two small-molecule fluorescent probes that we term ArsenoFluors (or AFs) as As-specific chemodosimeters. The AFs (AF1 and AF2) incorporate a coumarin fluorescent reporter coupled with an As-reactive benzothiazoline functional group. AFs react with As3+ to yield the highly fluorescent coumarin-6 dye (C6) resulting in a 20–25-fold fluorescence enhancement at λem ∼ 500 nm with detection limits of 0.14–0.23 ppb in tetrahydrofuran (THF) at 298 K. The AFs also react with common environmental As3+ sources such as sodium arsenite in a THF/CHES (N-cyclohexyl-2-aminoethanesulfonic acid) (1:1, pH 9, 298 K) mixture resul...