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A sensitive and reliable method was developed and validated for trace determination of sulfonylurea herbicides residues in cereals (wheat, rice, and corn) by liquid chromatography-tandem mass spectrometry. The selected analytes were ethoxysulfuron, ethametsulfuron-methyl, bensulfuron-methyl, chlorimuron-ethyl, pyrazosulfuron-ethyl, and cyclosulfamuron. In this work, the extraction procedure was performed by using a mixture solvent of phosphate buffer (pH 9.5)/acetonitrile (8:2, v/v) as the extraction solvent and then was cleaned up by using Spe-ed C18/18% SPE cartridges, providing good recoveries for all of the tested analytes and with no matrix effects affecting method accuracy. The limits of detection for the studied analytes in cereal samples were between 0.043 and 0.23 μg kg(-1), and the limits of quantification were between 0.14 and 0.77 μg kg(-1), lower in all cases than the maximum residue limits permitted by the European Union for this kind of food. The developed methodology has demonstrated its suitability for the monitoring of these residues in cereal samples with high sensitivity, precision, and satisfactory recoveries.

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A novel compound, diethyl(3-methylureido)(phenyl)methylphosphonate (DEP), possessing an organophosphate skeleton, was synthesized and used as a dummy template to prepare molecularly imprinted polymers (MIPs) for the recognition of organophosphate pesticide analogs. Computational modeling was used to study the primary intermolecular interactions in the prepolymerization mixture. It was found that the interaction force between DEP and the monomers was hydrogen bonding. A series of MIPs were synthesized with different monomers and were evaluated by adsorption experiments, which showed that methacrylic acid was used as an appropriate monomer and a molar ratio of DEP to MAA of 1 : 9 was optimal. Scatchard analysis showed that there might have been two types of binding sites in the MIPs. DEP and several pesticides were used in molecular recognition specificity tests of DEP-MIP, which exhibited better selectivity and reservation ability for organophosphate pesticides, such as methamidophos and orthene, possessing amino or imino groups and a smaller steric hindrance. On the basis of the use of a dummy molecule as template, the problem of template leakage could be avoided; this, thereby, improved the specificity of analysis.

Prochloraz is a fungicide that is widely used in citrus storage for attaining fruit disinfection. In this study, a gas chromatography method for determining prochloraz residues in mandarin orange by derivatization reaction of prochloraz into its main metabolite, 2,4,6‐trichlorophenol, was validated. Prochloraz residue levels in postharvest mandarin oranges at room temperature and cold storage were examined at recommended label use and exaggerated dosage. The results showed that the residue of prochloraz was found to be mostly distributed in mandarin orange peel. The decay rate of prochloraz in mandarin orange stored at room temperature was slightly faster than that in a refrigerator. It demonstrated that residue decay in pulp was slightly slower than that in the whole fruit. When treated with dipping application at 0.5 or 1 g/L dosage, final residues of prochloraz in mandarin oranges were found to be from 0.09 to 1.29 mg/kg at different storage conditions and intervals, which were far below the Codex MRL of 10 mg/kg. Residues at intervals of more than 7 days would be unlikely to pose any public health concerns if prochloraz was used according to the recommended use pattern at room temperature or cold storage. PRACTICAL APPLICATIONS Prochloraz is a fungicide that is widely used in citrus storage for preventing fruit disinfection. The present study was designed to evaluate the residue decay and final residue levels of prochloraz in postharvest mandarin orange (at different storage temperatures) at different sampling time, thus to confirm and recommend the safe use pattern of prochloraz for application in citrus fruits.

Cereal Chem. 88(5):441-444A method for determination of aluminum phosphide and magnesium phosphide residues in rice was developed and validated. This work, through good laboratory practices, demonstrated aluminum and magnesium phosphide residue dynamics in stored rice. Rice samples were treated with sulfuric acid, which hydrolyzed phosphides to phosphine (PH 3 ), which was simultaneously trapped in toluene. The organic layer was filtered and then analyzed by gas chromatography with a flame photometric detector. The PH 3 calibration curves showed a strong linear relationship in the range of 0.012-1.2 mg/L, with a correlation coefficient of 0.999. The limit of detection of this method was 0.004 mg/kg. The average recoveries from samples fortified with aluminum phosphide and magnesium phosphide ranged from 76.8 to 106.5% with relative standard deviations below 10.2% (n = 5). PH 3 was applied separately to rice samples to study dissipation dynamics at application dosages of 9.0 and 12 g/m 3 , respectively. The results showed half-lives of aluminum and magnesium phosphide in rice to be 1.84 and 1.53 days, respectively. PH 3 was applied once at low and high dosages. The low dosage was 4.5 g/m 3 of aluminum phosphide and 6.0 g/m 3 of magnesium phosphide, and the high dosage was 9.0 and 12 g/m 3 for these two formulations, respectively. The final PH 3 residues were below 0.013 mg/kg (limit of quantification).