| Pesticides play a very important role in human life. About 40% of current-used agrochemicals are chiral, and the proportion is increasing for that more and more complex chemicals are introduced. Enantiomers of chiral pesticides always show drastically stereoselective activity and toxicity. Hence, the separation and the purification of single-enantiomer are meaningful. Enantiomeric separations and analysis are the foundation for the study of enantioselectivity and environmental fate. Chiral recognition mechanism between enantiomers and chiral stationary phase (CSP) provides a theoretical guidance for separation. Determinating the elution order by high-performance liquid chromatography (HPLC) with R/S-configurations is basic data for enantioselective studies. All these data are not easy to obtain.Typical chiral triazole fungicides and aryloxyphenoxypropanoic acid (AOPP) herbicides were separated on several polysaccharide CSPs by normal phase HPLC. (1) Enantiomeric separations of 23 triazole fungicides were conducted on two polysaccharide CSPs (Chiralpak AD-H and Chiralcel OD-H columns, 250×4.6 mm i.d., 5μm). For most of the compounds, baseline separations were obtained on Chiralpak AD-H (resolution RS>1.5). Effect of mobile phase composition were evaluated on a binary and a ternary mobile phase systems, respectively. On the binary mobile phase system, isopropanol as the organic modifier showed better performance than ethanol. On the ternary system, the combined action of two modifiers could be adopted to the elution. The resolved enantiomers were distinguished by the signals of circular dichroism (CD) detector. The elution reversal was obtained when different alcohols (ethanol, isopropanol and/or methanol) were used in the mobile phase. Finally, the hydrogen-bonding interactions on chiral discriminations between triazole fungicides and the polysaccharide CSPs (ADMPC and CDMPC) were discussed with a molecular docking treatment. Except diniconazole, the hydrogen-bonding interactions of R/S-enantiomers occurred in different sites between the enantiomers and the CSPs. It was deduced that the hydrogen-bonding interaction is one of the main interactions for the discrimination of these fungicides.(2) Eight AOPP herbicides were well resolved on a Chiralpak AD-H column (250×4.6 mm i.d., 5μm) by a normal phase HPLC. The resolution was occurred with an n-hexane/ethanol mixture as the mobile phase (trifluoroacetic acid as the additive for acidic compounds) except haloxyfop with an n-hexane/isopropanol/TFA mixture. Chiral discriminations were mainly occurred with theπ-πinteractions, the dipole-dipole interactions and the hydrogen-bonding interactions. Besides, with the molecular docking treatment, it was deduced that the hydrogen-bonding interactions referred to the O, N atoms and carbonyl groups of enantiomers interacted with–NH group of ADMPC CSP. Furthermore, a method using HPLC tandem ultraviolet (UV) detector and CD detector was used to determine the elution order of R/S-enantiomers. Experimental CD-Cotton effect spectra of R/S-configurations were scanned in a stop-flow experiment. According to a quantum chemistry method, theoretical CD-Cotton effect spectra of R/S-configurations were calculated and simulated, and it was found that the R-configurations of these herbicides were corresponding to a positive-Cotton effect as R-(+)-enantiomer, and S-configurations were corresponding to a negative-Cotton effect as S-(–)-enantiomer, respectively. Comparison of the experimental CD and computed CD spectra indicated that the elution order of these herbicides were R>S for fluazifop-butyl, haloxyfop-methyl and haloxyfop-2-ethoxyethyl, and S>R for other AOPP herbicides under the specified separation conditions.(3) Silica gel with appropriated particle size (20μm), appropriated BET surface area (327.3482 m~2/g), pore volume (0.577156 cm~3/g) and pore size (60 ?) were synthesized as the carrier of chromatographic stuffing after reacted withγ-aminopropyltriethoxysilane. Moreover, Cellulose tris(4-methylbenzoate) (coated-CTMB) CSP was synthesized and then coated onto silica gel. Both an analytical column (250×4.6 mm i.d., 20μm) and a semi-prepared one (250×10 mm i.d., 20μm) were packed. Enantiomeric separation of diclofop-methyl was investigated on the analytical column, and the sufficient separation was obtained using n-hexane/isopropanol 85/15 as the mobile phase (RS 2.95). The elution order was R-(+)-diclofop-methyl>S-(–)-diclofop-methyl. By magnifying the column specification to a semi-one, the pure-enantiomer was purified with a handling collection treatment. The purification could meet a production with mg/h level.
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