Degradation of acephate and its metabolite methamidophos in rice during processing and storage

The degradation of acephate and its metabolite methamidophos during different stages of commercial processing, homing processing, and storage was assessed. Residues were determined by a simple gas-chromatographic method using a flame photometry detector. Acephate and methamidophos mostly remained in rice hull fractions, and hulling significantly reduced acephate and methamidophos in rice. Commercial processing caused the loss of 86% of acephate and 35.9% of methamidophos from rough brown rice to polished rice, whereas home processing caused the loss of 83.9% of acephate and 70% of methamidophos from polished rice to cooked rice. Washing for 5, 15, and 30 min (with tap water, 0.9% NaCl, and 0.1% Na₂CO₃) caused an average loss in the range of 9.8%-35.3% of acephate and 9.7%-45.2% of methamidophos. Extending washing time and adding a small amount of soda into the washing solution can efficiently eliminate acephate and methamidophos. The stability of acephate and methamidophos in polished rice was studied at different storage intervals, from 7 to 42 days at ambient temperatures (25 °C). Methamidophos was found to be more persistent than acephate.     

Degradation of acephate using combined ultrasonic and ozonation method

The degradation of acephate in aqueous solutions was investigated with the ultrasonic and ozonation methods, as well as a combination of both. An experimental facility was designed and operation parameters such as the ultrasonic power, temperature, and gas flow rate were strictly controlled at constant levels. The frequency of the ultrasonic wave was 160 k Hz. The ultraviolet-visible(UV-Vis) spectroscopic and Raman spectroscopic techniques were used in the experiment. The UV-Vis spectroscopic results show that ultrasonication and ozonation have a synergistic effect in the combined system. The degradation efficiency of acephate increases from 60.6% to 87.6% after the solution is irradiated by a160 k Hz ultrasonic wave for 60 min in the ozonation process, and it is higher with the combined method than the sum of the separated ultrasonic and ozonation methods. Raman spectra studies show that degradation via the combined ultrasonic/ozonation method is more thorough than photocatalysis. The oxidability of nitrogen atoms is promoted under ultrasonic waves. Changes of the inorganic ions and degradation pathway during the degradation process were investigated in this study. Most final products are innocuous to the environment.     

氧气饱和条件下乙酰甲胺磷的60Coγ辐射降解研究

利用60Coγ辐射降解有机磷农药乙酰甲胺磷的稀水溶液,以乙酰胆碱酯酶抑制率为指标,研究了氧气饱和不同吸收剂量条件下乙酰甲胺磷稀水溶液辐照前后的毒性变化;并采用高效液相色谱、离子色谱、气-质联用等检测手段对降解产物进行了分析。结合溶液毒性变化和降解率、生成的无机离子浓度、降解产物结构分析等,初步推导了氧气饱和条件下乙酰甲胺磷的辐射降解机理。     

Acephate and buprofezin residues in olives and olive oil

Field trials were carried out to study the persistence of acephate and buprofezin on olives. Two cultivars, pizz'e carroga and pendolino, with very large and small fruits respectively were used. After treatment, no difference was found between the two pesticide deposits on the olives. The disappearance rates, calculated as pseudo first order kinetics, were similar for both pesticides (on average 12 days). Methamidophos, the acephate metabolite, was always present on all olives, and in some pendolino samples it showed higher residues than the maximum residue limit (MRL). During washing, the first step of olive processing, the residue level of both pesticides on the olives did not decrease. After processing of the olives into oil, no residues of acephate or methamidophos were found in the olive oil, while the residues of buprofezin were on average four times higher than on olives.     

Acephate,methamidophos and monocrotophos residues in a laboratory‐scale oil refining process

Acephate, methamidophos and monocrotophos are insecticides used in oil palm plantations for the control of bagworms and leaf‐eating caterpillars. The main purpose of this study was to determine whether the physical refining process at laboratory scale, which simulated the manufacturing process, could remove the residues of these three insecticides in crude palm oil, in the unlikely event that crude palm oil were contaminated with these organophosphorus insecticides. A series of crude palm oil samples spiked with low (0.1 µg/g) and high (1.0 µg/g) levels of these insecticides were subjected to a laboratory‐scale physical oil refining process. Oil samples drawn at various stages of the refining process, namely, degumming, bleaching and deodorization, were analyzed using an in‐house analytical method. The results obtained from these experiments suggest that the physical refining process is capable of effectively removing residual insecticides from crude palm oil. The final product of crude palm oil refining, the refined, bleached and deodorized palm oil, was found to have no detectable levels of acephate, methamidophos and monocrotophos.