Abstract
The chiral separation of etoxazole enantiomers on Lux Cellulose-1, Lux Cellulose-3, Chiralpak IC, and Chiralpak AD chiral columns was carefully investigated by normal-phase high performance liquid chromatography and reverse-phase high performance liquid chromatography (HPLC). Hexane/isopropanol, hexane/n-butanol, methanol/water, and acetonitrile/water were used as mobile phase at a flow rate of 0.8 mL/min. The effects of chiral stationary phase, mobile phase component, mobile phase ratio, and temperature on etoxazole separation were also studied. Etoxazole enantiomers were baseline separated on Lux Cellulose-1, Chiralpak IC, and Chiralpak AD chiral columns, and partially separated on Lux Cellulose-3 chiral column under normal-phase HPLC. However, the complete separation on Lux Cellulose-1, Chiralpak IC, and partial separation on Chiralpak AD were obtained under reverse-phase HPLC. Normal-phase HPLC presented better resolution for etoxazole enantiomers than reverse-phase HPLC. Thermodynamic parameters, including ΔH and ΔS, were also calculated based on column temperature changes from 10 °C to 40 °C, and the maximum resolutions (Rs) were not always acquired at the lowest temperature. Furthermore, the optimized method was successfully applied to determine etoxazole enantiomers in cucumber, cabbage, tomato, and soil. The results of chiral separation efficiency of etoxazole enantiomers under normal-phase and reverse-phase HPLC were compared, and contribute to the comprehensive environmental risk assessment of etoxazole at the enantiomer level.
Highlights
Chiral pesticides have become a hotspot in the field of pesticide research
The chiral separation of etoxazole enantiomers was performed on normal-phase high performance liquid chromatography (HPLC) and reverse-phase HPLC (Figure S1)
When hexane/isopropanol (HEX/IPA) was used as mobile phase under normal-phase HPLC, etoxazole enantiomers could be baseline separated on Lux Cellulose-1, Lux Cellulose-3, Chiralpak IC, and Chiralpak AD chiral columns
Summary
About 30% of commercial pesticides are chiral [1,2]. Most commercial chiral pesticides are sold in the racemate form. Enantiomers of chiral pesticide have almost the same physical and chemical properties in achiral environments and generally different properties in chiral environments, including biological activity, metabolism, degradation, and toxicity [3,4,5,6,7,8,9]. With the increasing number of synthesized and registered. Molecules 2020, 25, 3134 number of synthesized and registered chiral pesticides introduced to market, it is urgent and necessary to investigate the environmental fates and toxicological risks of chiral pesticides at the chiral pesticides enantiomer level.introduced to market, it is urgent and necessary to investigate the environmental fates and toxicological of chiral pesticides at the enantiomer level.
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