Determination of 15 amide herbicides in rice using monolith column for on-line solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry

A method based on on-line solid-phase extraction (SPE) coupled with high performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of 15 amide herbicides in rice. A poly(butyl methacrylate-co-ethylene dimethacrylate) monolithic column was utilized as the solid-phase column. The sample was extracted with acetonitrile, cleaned up with the monolithic column in online mode. Subsequently, the analyte was eluted from the extraction column onto the analytical column (Hypersil GOLD column) by 0.5% (v/v) formic acid aqueous solution-acetonitrile in gradient elution mode. Electrospray ionization mass spectrometry was performed in the positive mode and multiple reaction monitoring (MRM) mode. Under the optimized conditions, good linearities were obtained with correlation coefficients of more than 0.998. The limits of detection (LODs) and limits of quantification (LOQs) were in the range 0.20 - 2.0 mu g/kg and 0.50 - 5.0 mu g/kg, respectively. The average recoveries were in the range 75.5% to 121. 3% at spiked levels of 2.0, 5.0, 10.0, and 50.0 mu g/kg for 14 amide herbicides and 5.0, 10.0, 50.0, and 100.0 mu g/kg for propanil. The relative standard deviations ranged from 2.89% to 12.38%. The proposed method is simple, rapid, and highly sensitive, and it can be applied to the simultaneous identification and quantification of the 15 amide herbicides in rice.