Determination of Abamectin Residue in Paddy Rice by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry

A new method for the conformation and quantification of abamectin residues in paddy rice was established based on ultra performance liquid chromatography-tandem mass spectrometry. The matrix effects for the method were studied. Paddy soil, paddy hull, brown rice and rice straw were extracted with acetonitrile by an oscillator, and cleaned up by C-18 SPE cartridge or florisil column. Paddy water was extracted with ethyl acetate by liquid-liquid partition, and cleaned up by C-18 SPE cartridge. The detection was performed by tandem mass spectrometry with electrospray ionization in positive mode (ESI+). Average recoveries of paddy soil, paddy water and brown rice at three spiked levels (1.0, 10.0 and 100 mu g/kg, or mu g/L) were found in the range of 84%-107% with RSD<13.6%. Average recoveries of paddy hull and rice straw at two spiked levels (10.0 and 100 mu g/kg) were found in the range of 90%-103% with RSD<12.9%. Limits of detection(LODs)of abamectin in paddy soil, paddy water and brown rice were 0.3 mu g/kg, which were lower than the maximum residue limit (MRL) established by the Japanese and the European legislation in rice (10 mu g/kg). Limits of detection (LODs) of abamectin in paddy hull and rice straw were 3.0 mu g/kg. A good linear relationship was obtained in the range of 2.0-100 mu g/L with the correlation coefficient (r) over 0.999.