Simultaneous quantification of Hg²⁺ and MeHg⁺ in aqueous media with a single fluorescent probe by multiplexing in the time domain

Development of a molecular probe for selective detection of MeHg⁺ in the presence of Hg²⁺ is a mission impossible to accomplish. Speciation analysis of two substrates with a single kinetic trace exploiting their differential reactivity toward a single probe, i.e., multiplexing in the time domain, is a cost-effective and powerful alternative. We have developed such a probe (Hg410) for simultaneously quantification of Hg²⁺ and MeHg⁺ in aqueous media. Hg410 is designed via the "covalent-assembly" approach, displays a zero background, and bears a very concise molecular construct. It has harnessed proximity-based catalysis to achieve high reactivity toward Hg²⁺ and MeHg⁺. An unprecedentedly low detection limit of ca. 4.6 pM and 160 pM was measured for Hg²⁺ and MeHg⁺, respectively.