Determination of Ethiprole Enantiomers Residue in Rices Using Solid Phase Extraction-Liquid Chromatography Tandem Mass Spectrometry

A simple and sensitive enantioselective method for the determination of ethiprole enantiomers in rice was developed by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Ethiprole was enantioseparated with three cellulose-based chiral stationary phases by HPLC-MS/MS. The effects of the mobile phase and column on the enantiosepartion were studied. The direct resolution of ethiprole enantiomers was performed on a cellulose tris (3, 5-dimethylphenylcarbamate) column (Lux Cellulose-2) using methanol-water (60 : 40, V/V) as mobile phase, and (+)-ethiprole and (-)-ethiprole were eluted and determined by a circular dichroism (CD) detector. The ethiprole residues in rice samples were extracted with acetonitrile and cleaned by NH2 column chromatography.HPLC-MS/MS with electrospray in negative ion scan mode was used to determine ethiprole enantiomers. The fortified recoveries of ethiprole enantiomers in rice matrices including polished rice and brown rice were 87.4%-97.8% at fortification levels ranging from 0.01 to 0.2 mg/kg. Relative standard deviations were 3.1%-9.3%. The limits of quantification for ethiprole enantiomers were both 0.003 mg/kg.