Residue Analysis Of Propiconazole Enantiomers In Banana Leave

In this study,a new high performance liquid chromatography-tandem mass spectrometry（HPLC-MS/MS）method was developed for the analytical determination of the enantiomers content of propiconazole in banana leaves.A Superchiral S-OX（3μm）column baseline was used to separate the four enantiomers of propiconazole.The absolute configuration of the cis-propiconazole enantiomers were determined by X-ray single-crystal diffraction.The differences in the inhibitory activity of the four enantiomeric isomers of propiconazole against Curvularia lunata,Colletotrichum musae,Nigrospora oryzae,and Colletotrichum fructicola were evaluated.In the three main banana producing areas of China（Guangdong,Guangxi and Hainan）,the differences in degradation behaviors of the four enantiomers of propiconazole in banana leaves were investigated.This study provides a reference method for residue analysis and detection of multi-chiral centered propiconazole in complex matrix samples,and provides a scientific basis for further development of highly efficient,low toxicity and low residue single chiral pesticides.In this paper,the effects of five chiral columns,different mobile phases and different column temperatures on the separation of the four enantiomers of propiconazole were investigated.The baseline separation of the four enantiomers of propiconazole was finally determined using a Superchiral S-OX（3μm）column with a column temperature of 40℃and a mobile phase of 100%ethanol.The absolute configuration of the cis-propiconazole enantiomers were determined as（2R,4S）-（+）-propiconazole and（2S,4R）-（-）-propiconazole by X-ray single-crystal diffraction.The absolute conformations of the trans-propiconazole enantiomers were identified as（2R,4R）-（+）-propiconazole and（2S,4S）-（-）-propiconazole by supercritical fluid chromatography tandem mass spectrometry（SFC-MS/MS）in comparison with references.Finally,the order of the peaks of the four enantiomers of propiconazole on the Superchiral S-OX（3μm）column was determined as（2R,4R）-（+）-propiconazole,（2R,4S）-（+）-propiconazole,（2S,4S）-（-）-propiconazole and（2S,4R）-（-）-propiconazole.The differences in the inhibitory activities of four enantiomers and racemates of propiconazole against four plant fungi（Curvularia lunata,Colletotrichum musae,Nigrospora oryzae and Colletotrichum fructicola）were evaluated by mycelial growth rate inhibition.The results showed that（2R,4S）-（+）-propiconazole had the highest inhibitory activity against the four target plant fungi among the five agents,with EC₅₀values of 0.156μg/m L,0.089μg/m L,0.704μg/m L and 0.176μg/m L for（2R,4S）-（+）-propiconazole against Curvularia lunata,Colletotrichum musae,Nigrospora oryzae and Colletotrichum fructicola,respectively.From May 2019 to October 2020,field trials were conducted in three major banana producing areas in Guangdong,Guangxi and Hainan to investigate the residue behavior and stereoselective degradation behavior of propiconazole enantiomers on banana leaves.In this paper,a better（less than 26 min analysis time）method for the determination of propiconazole residues in banana leaves by HPLC-MS/MS analysis was developed for the first time.The samples were extracted by ultrasonic vortexing with acetonitrile and cleaned up by an Oasis PRIME HLB solid phase extraction column.The average recoveries of the four enantiomeric isomers of propiconazole in banana leaves at the spiked levels of 0.1,2 and 10 mg/kg（total concentration of the four enantiomeric isomers）ranged from 76.3%to 103.4%with the relative standard deviations（RSDs）of 1.25%-11.40%.The limits of detection（LODs）of the four enantiomeric isomers of propiconazole in banana leaves were 0.0007 mg/kg and the limits of quantification（LOQs）were 0.02 mg/kg.The half-lives of the four stereoisomers of propiconazole in banana leaves from Guangdong were 6.24-7.45days;the half-lives of the four stereoisomers of propiconazole in banana leaves from Guangxi were 8.35-11.55 days;the half-lives of the four stereoisomers of propiconazole in banana leaves from Hainan The half-lives of the four stereoisomers were 9.76-14.14 days in banana leaves from Hainan.The results from all three sites indicated that the degradation rate of（2S,4S）-（-）-propiconazole in banana leaves was slightly faster than that of（2R,4R）-（+）-propiconazole and（2R,4S）-（-）-propiconazole in banana leaves was slightly faster than that of（2R,4S）-（+）-propiconazole.