Identification of Rotenone and Five Rotenoids in CFT Legumine Piscicide Formulation via High-Resolution Mass Spectrometry and a New High-Throughput Extraction Procedure

The piscicide CFT Legumine is applied to freshwater systems around the world to control invasive fish species. Rotenone, a potent inhibitor of mitochondrial cellular respiration, is the active ingredient of the piscicide; however, other rotenoids of unknown persistence and toxicity account for an equivalent amount by weight. This work identified six distinct rotenoids in CFT Legumine using liquid chromatography coupled with high-resolution orbitrap mass spectrometry and optimized a rapid surface water sampling procedure for their analysis. The rotenoids were identified as rotenone and its isomer deguelin, their 12α-hydroxylated products rotenolone and tephrosin, as well as 6α,12α-dehydrorotenone and 6α,12α-dehydrodeguelin. The optimized procedure, extraction with Spin-X nylon membrane microcentrifuge filters followed by elution with acetonitrile, achieved recoveries ranging from 101 to 107% and 97 to 145% for all six rotenoids at high (125 nM, ~ 50 ppb) and low (25 nM, ~ 10 ppb) concentrations of CFT Legumine, respectively. Overall, this method provides a rapid sampling procedure necessary for monitoring rotenoid persistence in surface water to ensure safe and efficacious application of the pesticide.