A rapid and simple extraction method for the simultaneous analysis of five neonicotinoid insecticides has been developed. Twelve different fruit and vegetable matrixes were extracted with methanol and cleaned up using a graphitized carbon solid phase extraction cartridge loading with a 20% methanol solution. The concentrated eluate after methanol elution was then analyzed for pesticide residues by liquid chromatography/mass spectrometry in the APCI positive mode. The five pesticides including nitenpyram, thiamethoxam, imidacloprid, acetamiprid, and thiacloprid were recovered at 70-95% at spike levels of 0.1 and 1 mg/kg in bell pepper, cucumber, eggplant, grape, grapefruit, Japanese radish, peach, pear, potato, rice, and tomato. Relative standard deviations were less than 10% for all of the recovery tests. The proposed method is fast, easy to perform, and could be utilized for regular monitoring of pesticide residues.
A method was established for the determination of 180 pesticide residues in fruits and vegetables. The procedure involved extraction with acetonitrile, followed by a salting-out step with anhydrous MgSO 4 and NaCl. Removal of sediment and water was performed simultaneously by centrifugation. Co-extractives were removed with a double-layered SPE column, and graphitized carbon black and primary secondary amine (GCB/PSA) solid phase extraction cleanup cartridge. The eluate was determined by GC/FPD and GC/MS without further cleanup. Recovery data were obtained by fortifying 9 matrices at 0.05-0.1 mg/g. Recoveries of 180 pesticides were mainly 70-110% and the relative standard deviation (RSD) was below 25%. Limits of detection ranged between 0.01 and 0.05 mg/g for tested pesticides.
A monitoring plan of residual antibiotics in food of animal origin was conducted in Vietnam from 2012 to 2013. Meat samples were collected from slaughterhouses and retail stores in Ho Chi Minh City and Nha Trang. A total of 28 antibiotics were analyzed using a LC-MS/MS screening method. Sulfonamides, fluoroquinolones, and tilmicosin were detected in some of the samples. Sulfaclozine and fluoroquinolones were mainly detected in chicken samples, and sulfamethazine was mainly detected in pork samples. High levels of sulfonamide residues, ranging between 2500 and 2700 μg/kg sulfaclozine and between 1300 and 3600 μg/kg sulfamethazine, were present in two chicken and three pork samples, respectively. Tilmicosin was detected at ranges of 150-450 μg/kg in 10 chicken samples. Positive percentages were 17.3, 8.8, and 7.4% for chicken, pork, and beef, respectively, for an average of 11.9%. The results suggest an appropriate withdrawal period after drug administration had not been observed in some livestock.
Residual organophosphorus pesticides in foods were determined by accelerated solvent extraction (ASE), gel permeation chromatography and GC-FPD. Pesticides were extracted at 100 degrees C under 1500 psi pressure in less than 20 min. Wet samples were extracted after mixing with Extrelut drying agent. Four foods were spiked with 19 pesticides at 0.1 ppm or less. The average recoveries of these pesticides were 80-90% and the precision was < 10%. Both methamidophos and acephate gave 37-50% recoveries and 6-40% precision. These results suggested that ASE can be used to extract residues of organophosphorus pesticides in foods.
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