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Using fluorescence to detect biologically relevant metals has been studied extensively due to its rapid and low detection limit ability. Sodium and potassium differentiation is significant in diagnosis of many medical conditions. For this, we designed coumarin dimers as flexible fluorescent probes using ethylene glycol units for differentiation of sodium and potassium. To our best knowledge, use of these easy-to-synthesize coumarin dimers linked through ethylene glycol units are first in the literature. In fluorescence titration experiments, diethylene glycol linked coumarin-3-carboxylate dimer is responsive for sodium ions but not for potassium ions. The driving force for the complexation of metal cation and fluorescence probes is thought to be size-matching. To further explain the phenomenon, we synthesized coumarin dimer using 1,8- octanediol as the linker, and methyl ester of coumarin-3-carboxylic acid to investigate the effect of structural changes on the fluorescence intensity. These two compounds could not differentiate the sodium and potassium. Flexible coumarin dimers as fluorophores are shown to be useful for sensing sodium cation in the presence of potassium cation.

The westslope cutthroat trout, Oncorhynchus clarkii lewisi , has experienced substantial declines across its historic range. Natural resource managers have actively worked to restore populations using piscicide treatments to remove competing non-native trout prior to repatriation of the species. Rotenone is commonly employed as a piscicide treatment in streams, followed by the application of potassium permanganate to detoxify rotenone so as not to adversely affect native trout that may inhabit downstream areas. However, at certain concentrations potassium permanganate can also cause trout mortality. We placed five westslope cutthroat trout in each of four live carriers within a potassium permanganate detoxification zone to determine if and when in situ levels of potassium permanganate resulted in trout mortality. After application of potassium permanganate, we monitored its concentration and trout mortality in the carriers every hour for five hours. Westslope cutthroat trout mortality was 100% after five hours of exposure, with a mean potassium permanganate concentration of 2.96 ± 0.19 (SE) mg/L over the duration of the experiment. Our results suggest that for treatment times of five hours, residual potassium permanganate concentrations should be below 2.96 mg/L for westslope cutthroat trout to survive downstream of rotenone treatments in a detoxification zone.