Enantioselective separation and simultaneous determination of fenarimol and nuarimol in fruits, vegetables, and soil by liquid chromatography–tandem mass spectrometry

Enantioseparation, Absolute Configuration, and Enantioselective Bioactivity Mechanism of the Chiral Fungicide Nuarimol

In this study, the nuarimol enantiomers were successfully baseline separated with Rs 1.70 by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The absolute configurations of the nuarimol enantiomers were confirmed as R-(+)-nuarimol and S-(-)-nuarimol. The enantioselective bioactivity assay indicated that R-(+)-nuarimol exhibited greater potency against seven phytopathogenic fungi, with values approximately 1.4-3.5 and 4.5-51.4 times higher than those of rac-nuarimol and S-(-)-nuarimol. The active contribution value of R-enantiomer was 82-98%, showing that R-(+)-nuarimol played a crucial role in bioactivity. Meanwhile, R-(+)-nuarimol exhibited stronger effects in increasing the cell membrane permeability, compromising the cell membrane integrity, and inhibiting ergosterol biosynthesis. Molecular docking analysis showed that R-(+)-nuarimol possessed a stronger binding affinity to sterol 14-α demethylase (CYP51) than S-(-)-nuarimol, with docking energies of -7.42 and -7.36 kcal/mol. This study contributes essential data for screening a high-activity enantiomer of nuarimol and provide guidance for reducing used dosage and increasing the efficiency of nuarimolAQ.

Enantioselective degradation of Myclobutanil and Famoxadone in grape

The enantioselective degradation of myclobutanil and famoxadone enantiomers in grape under open field was investigated in this study. The absolute configuration of myclobutanil and famoxadone enantiomers was determined by the combination of experimental electronic circular dichroism (ECD) and calculated ECD spectra. The enantiomers residues of myclobutanil and famoxadone in grape were measured by sensitive high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS). The linearity, precision, accuracy, matrix effect, and stability were assessed. And the limit of quantification (LOQ) for each enantiomer of myclobutanil and famoxadone in grape was evaluated to be 1.5 and 2 μg kg^-1. The myclobutanil and famoxadone showed the enantioselective degradation in grape, and the enantioselectivity of degradation for myclobutanil was more pronounced than that for famoxadone. The half-lives were 13.1 days and 25.7 days for S-(+)-myclobutanil and R-(-)-myclobutanil in grape, separately. The half-life of S-(+)-famoxadone was 31.5 days slightly shorter than that of R-(-)-famoxadone with half-life being 38.5 days in grape. The probable reasons for the enantioselective degradation behavior of these two fungicides were also discussed. The results in the article might provide a reference to better assess the risks of myclobutanil and famoxadone enantiomers in grapes to human and environment. Graphical abstract The enantioselective analysis of myclobutanil and famoxadone in grape.

Simultaneous enantioselective determination of phenylpyrazole insecticide flufiprole and its chiral metabolite in paddy field ecosystem by ultra-high performance liquid chromatography/tandem mass spectrometry

A novel and sensitive ultra-high performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous enantioselective determination of flufiprole and its hydrolysis metabolite in paddy field ecosystem. The separation and determination were performed using reversed-phase chromatography on a novel cellulose chiral stationary phase, a Lux Cellulose-4 (150 mm × 2.0 mm) column, under isocratic conditions at 0.25 mL/min flow rate. The effects of other four different polysaccharide-based chiral stationary phases (CSPs) on the separation and simultaneous enantioseparation of the two target compounds were also evaluated. The elution orders of the eluting enantiomers were identified by an optical rotation detector. Modified QuEChERS (acronym for Quick, Easy, Cheap, Effective, Rugged and Safe) method and solid-phase extraction (SPE) were used for the enrichment and cleanup of paddy water, rice straw, brown rice and paddy soil samples, respectively. Parameters including the matrix effect, linearity, precision, accuracy and stability were evaluated. Under the optimal conditions, the mean recoveries for all enantiomers from the above four sample matrix were ranged from 83.6% to 107%, with relative standard deviations (RSD) in the range of 1.0-5.8%. Coefficients of determination R(2)≥0.998 were achieved for each enantiomer in paddy water, rice straw, brown rice and paddy soil matrix calibration curves within the range of 5-500 μg/kg. The limits of quantification (LOQ) for all stereoisomers in the above four matrices were all below 2.0 μg/kg. The methodology was successfully applied for simultaneously enantioselective analysis of flufiprole enantiomers and their chiral metabolite in the real samples, indicating its efficacy in investigating the environmental stereochemistry of flufiprole in paddy field ecosystem.

Green and sensitive supercritical fluid chromatographic-tandem mass spectrometric method for the separation and determination of flutriafol enantiomers in vegetables, fruits, and soil

A green and sensitive chiral analytical method was developed to determine flutriafol enantiomers in vegetables (tomato, cucumber), fruits (apple, grape), and soil by supercritical fluid chromatography-tandem mass spectrometry. The enantioseparation was performed within 3.50 min using Chiralpak IA-3 column with CO2/methanol (88:12, v/v) as the mobile phase at a 2.2 mL/min flow rate. The postcolumn compensation technology provided with 1% formic acid/methanol greatly improved the ionization efficiency of mass spectrometry. Column temperature, auto back pressure regulator pressure, and flow rate of compensation solvent were optimized to 30 °C, 2200 psi, and 0.1 mL/min, respectively. The simple and fast QuEChERS pretreatment method was adopted. Mean recoveries for flutriafol enantiomers were 77.2-98.9% with RSDs ≤ 9.6% in all matrices. The limits of quantification ranged from 0.41 to 1.18 μg/kg. Well-applied to analyze authentic samples, the developed method could act as a versatile strategy for the analysis of flutriafol enantiomers in food and environmental matrices.