Analysis of Tebuconazole and Tetraconazole Enantiomers by Chiral HPLC-MS/MS and Application to Measure Enantioselective Degradation in Strawberries

Abstract

A rapid and sensitive enantioselective method for the determination of tebuconazole and tetraconazole enantiomers in strawberry has been developed. The enantiomers were resolved by high-performance liquid chromatography on a cellulose tris (3-chloro-4-methylphenylcarbamate) (Lux Cellulose-2) column using methanol–0.1% formic acid solution (70:30, v/v) as mobile phase. The chiral liquid chromatographic separation was combined with an extract/cleanup procedure known as the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. High-performance liquid chromatography-tandem mass spectrometry with electrospray ionization was then used for qualitative and quantitative determination of the enantiomers of tebuconazole and tetraconazole. Hexaconazole was used as an internal standard. The method provided high selectivity and sensitivity, and the limits of quantification for tebuconazole and tetraconazole enantiomers in strawberry were both 2.5 μg/kg. The method was successfully utilized to investigate the probable enantioselective degradation of tebuconazole and tetraconazole in strawberry. The results showed that the degradation of the tebuconazole and tetraconazole enantiomers in strawberry followed first-order kinetics (R 2 > 0.96). The results from this study revealed the degradation of tetraconazole in strawberry was not enantioselective, while the degradation of tebuconazole was enantioselective, and the (+)-tebuconazole showed a faster degradation than (−)-tebuconazole in strawberry. The results could provide a reference to fully evaluate risks of these two fungicides.