Fast and accurate on-site determination of rotenone in water during fish control treatments using liquid chromatography

Summary

A fast, accurate and simple method using liquid chromatography (LC) with UV detection was used for the on-site determination of the piscicide rotenone in water during fish control treatments. Sample volumes of 10 to 40 μL were loaded onto a Waters XBridge™ C18 2.5 μm 3.0 x100 mm analytical column using a mobile phase of water–acetonitrile (45:55) at a flow-rate of 0.5 mL/min. The method was evaluated using river and estuarine water spiked with rotenone (0.1–330 μg/L) and various preservation methods. The within-assay precision measured as relative standard deviation (RSD, n = 12) was 5.5 to 6.5% and the between assay precision (RSD, n = 4) was 6.5 to 7.5%. The limit of quantification was 1 μg/L, below normal piscicidal treatment rates (5 to 200 μg/L) and regulatory limits (< 2 μg/L) generally considered safe. The analysis time was 6 min/sample allowing for real-time adjustment of rotenone dosages during fish control treatments. The relatively small size (75×60×50 cm) of the LC system made it ideal for transportation and installation in remote treatment areas; it can be operated out of a small trailer in the field with electricity. Our studies indicate that the preservation of water samples with equal quantities of acetonitrile stabilizes rotenone indefinitely (> 170 days) if kept cool (4 °C) and in the dark. Although increased salinity decreased the recovery of rotenone, sample filtration with Spin-X filter membranes negated the effect.