Determination of rotenoids and piperonyl butoxide in water, sediments and piscicide formulations

Abstract

Rotenone is a naturally occurring insecticide and piscicide (fish poison) found in many leguminous plants. This paper describes high-performance liquid chromatography (HPLC) methods for the quantitative analysis of rotenone's principal biologically active components (rotenone, tephrosin, rotenolone, deguelin) and the synergist piperonyl butoxide (PBO) in various media. Compounds were separated on a C₁₈ reversed phase column with an acetonitrile–0.025 M phosphoric acid mobile phase and detected by UV absorbance or fluorescence (PBO only). Solid phase extraction (SPE) was used in either coupled (on-line) mode with a C₁₈ concentrator column or automated off-line mode using Empore C₁₈ disks. The on-line extraction efficiency was improved significantly by adding small amounts of methanol to water. Method detection limits (MDLs) for rotenoids and PBO in reagent water were 0.3 and 2 µg L^–1, respectively, with optimal recoveries ranging from 90% to 99%. Aquatic sediments were extracted with methanol and the extracts were diluted in water prior to analysis by coupled SPE-HPLC. In wet sediments, detection limits were approximately 20–100 µg kg^–1 with recoveries of 71% to 87%. Sonication in dimethyl sulfoxide (DMSO) followed by dilution in acetonitrile and filtration allowed determination of the active ingredients in powdered rotenone formulations. Details of sample preparation, cartridge column cleanup and analyte confirmation are provided.