Oxidation-Resistant Fluorogenic Probe for Mercury Based on Alkyne Oxymercuration

Mercury continues to be a major safety hazard to the general public. Therefore, a fluorescence method that has potential for on-site use can be very useful. Most fluorescent probes for mercury are based on the interaction between mercury ions and sulfur atoms, which may not be compatible with mercury samples prepared by oxidation processes. Herein we report a fluorogenic probe for mercury based on the unique ability of Hg2+ to convert an alkyne to a ketone. By this methodology, the probe, prepared in two steps in 80% overall yield, is converted to a very bright green fluorescent molecule by Hg2+ in pH 7 buffer. This fluorescence method is sensitive, showing a signal-to-background ratio of 3 at 8 ppb mercury level, and highly specific for this metal ion. Since this detection method does not rely on mercury-heteroatom interactions, the probe is resistant to oxidants and thus can be used against mercury samples prepared by oxidative procedures. We demonstrate that our method can be applied to fish and dental samples.