In this study, we separate enantiomers of bifenthrin, a pyrethroid insecticide, by using high performance liquid chromatography
with a chiral stationary phase (CPS) column. Toxicity tests of bifenthrin enantiomers were performed with Daphnia (water flea,
Daphnia pulex), tilapia fish (Tilapia spp.) and carp fish (Cyprinus carpio). Two enantiomers of bifenthrin were separated successfully
by injecting 20 μL of bifenthrin 1000 mg/L standard solution into a Sumichiral OA-2500-I column. The mobile phase solvent system
was composed of n-hexane, isopropanol, and ethanol in a ratio of 99.8/0.06/0.14, and the flow rate was 1.0 mL/min. Both enantiomers
were eluted within 20 min. Two separated enantiomers, (-)-bifenthrin and (+)-bifenthrin, were identified by gas chromatography
with mass spectrometry detector (GC-MSD) and polarimeter. Each enantiomer of bifenthrin and the standard bifenthrin solution
showed the same fragmentation pattern spectrum. The fragment ions were m/z 115, m/z 141, m/z 165, m/z 181, and m/z 422. The
specific rotations [α]20
365 of (-)-bifenthrin and (+)-bifenthrin were -66.41° and +69.63°, respectively. In the toxicity study, the LC50
(12 hr) of (-)-bifenthrin and (+)-bifenthrin for daphina were 2.1 μg/L and 28.9 μg/L, respectively. On the other hand, the result of fish toxicity indicated the LC50 (96 hr) of (-)-bifenthrin and (+)-bifenthrin for carp (C. carpio) were 0.99 and 2.08 μg/L, respectively, and for tilapia (Tilapia spp.) were 0.19 and 0.80 μg/L, respectively. The study of biological activity showed that the toxicity of (-)-bifenthrin was 10-fold greater than (+)-bifenthrin for Daphnia, and 2-fold greater for fish. This study provided improved methods for separating enantiomers of bifenthrin and assessing hazard of individual enantiomers toward non-target aquatic fauna.