Determination of field-incurred pyrimethanil residues in persimmon (Diospyros kaki Linn) by liquid chromatography.

Field trials have been carried out to determine the residues of the fungicide pyrimethanil in persimmon (Diospyros kaki Linn) after field treatment. Three treatments using pyrimethanil (PYR 30% WP) were carried out on persimmon trees at a recommended dose rate: the former was sprayed at two different times at 30 and 21 days prior to harvesting; the second was sprayed three times at 40, 30 and 21 days prior to harvesting; and the third was sprayed four times at 40, 30, 21 and 14 days prior to harvesting. The analysis was based on liquid-liquid extraction and solid-phase extraction followed by liquid chromatography with ultraviolet detection at 268 nm. Pyrimethanil was confirmed by high-performance liquid chromatography-mass spectrometry HPLC-MS in the selected ion monitoring mode. The method was validated with spiked fruit samples at concentrations of 0.1 and 0.4 ppm. Average recoveries (three replicates) ranged from 87.1 to 92.1% with relative standard deviations between 4.5 and 11.98%. The calculated limit of detection was 0.02 ppm and the limit of quantitation was 0.07 ppm. After two, three or four applications, pyrimethanil residues on persimmon averaged 0.44, 0.48 or 0.53 ppm, respectively; all of these values were below the maximum residue level established by the Korean Food and Drug Administration (5.0 ppm). This indicates that pyrimethanil residues declined to a level well below the maximum residue level within the 14 day period between the last application and harvesting.

A multiresidue method for the analysis of pesticide residues in polished rice (Oryza sativa L.) using accelerated solvent extraction and gas chromatography and confirmation by mass spectrometry.

An analytical procedure using accelerated solvent extraction and gas chromatography with an electron capture detector has been optimized to simultaneously determine the residue of two insecticides (diazinon and EPN) and one fungicide (isoprothiolane) in polished rice and was confirmed by GC-mass spectrometry. Several parameters, including temperature, pressure, solvent ratio, cell size and cell cycle, were thoroughly investigated to find the optimal extraction conditions. The average recoveries of the three pesticides were between 82.7 and 126.4% at spiking levels of 0.1 and 0.5 ppm. The relative standard deviations were less than 7% for all of the recovery tests. The optimum accelerated solvent extraction operating conditions were 100 degrees C, 1500 atm, acetone-n-hexane (20:80 v/v) as the extraction solvent, two cycles, and a cell size of 33 ml. The total extraction time was approximately 20 min. The optimized procedure has also been applied to the determination of diazinon, isoprothiolane and EPN in real rice samples. In conclusion, accelerated solvent extraction was used for the first time for the analysis of diazinon, isoprothiolane and EPN in polished rice and offers the possibility of a fast and simple process for obtaining a quantitative extraction of the studied pesticides.