No abstract

To assess the photodegradation extent of the organophosphorus pesticides, fenthion and disulfoton in the environment, degradation rates of their chemicals under irradiation by visible light and each region of the ultraviolet (UV) sources, UVA (320-400 nm radiation), UVB (280-320 nm radiation) and UVC (250-260 nm radiation) in liquid-and solid-phases were determined and their photolysis products identified. Although visible light did not cause photodegradation of either fenthion or disulfoton even after the maximal irradiation of 8 hr in both phases, all the ranges of UV sources resulted in the photolysis of both pesticides, despite the solid-phase. The photolysis rates of fenthion under UVB and UVC irradiation in both phases were higher than that under UVA irradiation and also exceeded all of the degradation rates of disulfoton. This confirms that fenthion is more readily degraded than disulfoton in the UVB range. Fenthion sulfoxide and disulfoton sulfoxide were identified as oxidative photolysis products whose photolysis rates were considerably slower than parent compounds, and the oxidation reaction of both pesticides in the liquid-phase was superior to those on the solid-phase, indicating that dissolved oxygen in water is an important factor affecting the photolysis. These results suggest that fenthion in the environment is more rapidly degraded by UVB irradiation in natural sunlight than disulfoton, and sulfoxides of both pesticides remain stable as a photolysis product in the environment.

Validation of multiresidue screening methods for the determination of 186 pesticides in 11 agricultural products: broccoli, asparagus, carrot, spinach, burdock, matsutake mushroom, cauliflower, orange, soybean, sesame and millet was done by gas chromatography (GC). The investigated pesticides were selected on the based of such compounds that are commonly used around the world. Although the recovery of 58 of the pesticides was low (< 50%) in some crops, the 128 pesticides that spiked in samples at 0.1 mg/kg showed satisfactory recoveries (≥ 50%) in all crops with relative standard deviation of 4-21%. These validated 128 pesticides were therefore newly acceptable for the pesticide-monitoring programme at the Quarantine Station in Japan; the quantitative limits ranged from 0.005 to 0.1 ppm by GC on a crop basis. The screening methods were applied to monitor the residue from a total of 200 pesticides including 72 previously validated in imported foods at the Station in Japan. Pesticide residue from 188 (12.4%) was found in 1516 samples. Of these, 4 (0.26%) were in violation of Japanese maximum residue limits (MRLs). No detectable residue was found in 1328 (87.6%) samples.

The aim of this study was to elucidate the presence of vitamin E homologues in medicinal plants. To identify various homologues in the matrix of medicinal plant samples, a method for simultaneous determination was developed using ESI(+)-LC-MS3. A complete separation of each homologue was achieved within 20 min using a PFP column and an isocratic elution system of water/methanol (10:90, v/v) at a flow rate of 0.5 mL/min. The ESI-MS condition for each homologue was optimized, and the m/z value and the fragmentation pathway of each homologue were summarized. This LC-MS3 method made it possible to detect the homologues without the effect of matrix; therefore, high sensitive analysis was established, and then, the MS3 makes it possible to extract from plants with methanol only. The LC-MS3 method was applied to identify the eight vitamin E homologues in 11 medicinal plants.