A modified quick, easy, cheap, effective, rugged (QuEChERS) method with multi-walled carbon nanotubes (MWCNTs) as reversed-dispersive solid phase extraction (r-DSPE) material was applied to the analysis of pirimiphos-methyl and deltamethrin residues in stored rice. Two dustable powder (DP) formulations (2% pirimiphos-methyl and deltamethrin DP; 5% pirimiphos-methyl DP) were applied in simulated storehouse trials in the lab. The residues and dissipation of the two pesticides in stored rice were investigated. Slow dissipation of both pesticides was observed in stored rice. The half-lives of pirimiphos-methyl were 23.9–28.9 days, and those of deltamethrin were 23.9–24.8 days. Residues of pirimiphos-methyl from application rates of 4.5–6.75 a.i. mg/kg (active ingredient milligram per kilogram) and 10–15 a.i. mg/kg were 1.6–3.8 mg/kg and 3.0–4.5 mg/kg at 60 days Pre-harvest Interval (PHI). Residues of deltamethrin from an application rate of 0.5–0.75 a.i. mg/kg were 0.13–0.14 mg/kg at 60 days PHI. Both pesticides residues were below the Maximum Residue Limits (MRLs) established by the Codex Alimentarius Commission (CAC). Therefore, at the recommended dosages they are safe for use on stored rice.
An analytical method based on dispersive solid-phase extraction with a multiwalled carbon nanotubes sorbent coupled with positive pulse glow discharge ion mobility spectrometry was developed for analysis of 30 pesticide residues in drinking water samples. Reduced ion mobilities and the mass-mobility correlation of 30 pesticides were measured. The pesticides were divided into five groups to verify the separation capability of pulse glow discharge in mobility spectrometry. The extraction conditions such as desorption solvent, ionic strength, conditions of adsorption and desorption, the amounts of multiwalled carbon nanotubes, and solution pH were optimized. The enrichment factors of pesticides were 5.4- to 48.7-fold (theoretical enrichment factor was 50-fold). The detection limits of pesticides were 0.01∼0.77 μg/kg. The linear range was 0.005-0.2 mg/L for pesticide standard solutions, with determination coefficients from 0.9616 to 0.9999. The method was applied for the analysis of practical and spiked drinking water samples. All results were confirmed by high-performance liquid chromatography with tandem mass spectrometry. The proposed method was proven to be a commendably rapid screening qualitative and semiquantitative technique for the analysis of pesticide residues in drinking water samples on site.
A palladium-catalyzed asymmetric tandem [3+2] cycloaddition/allylation of methylene-trimethylenemethane is presented, providing the functionalized chiral hexahydropyrazolo[5,1- a]isoquinoline derivatives in high yields with good to excellent enantioselectivities and moderate to good E: Z ratios. In the one-pot sequential tandem reactions/hydroxylation, ( E)-allylic alcohol products were obtained in good yields with excellent enantioselectivities.
Ochratoxin A (OTA) is a potential human carcinogen that poses a significant concern in food safety and public health. OTA has been found in a wide variety of agricultural commodities, including cereal grains. This study investigated the reduction of OTA during the preparation of rice- and oat-based porridge by a simulated indirect steam process. The effects of sodium bicarbonate (NaHCO3) and fructose on the reduction of OTA were also investigated. During the processing, OTA in rice- and oat-porridge was decreased by 59% and 14%, respectively, from initial OTA artificially added at 20 μg/kg (dry weight basis). When 0.5% and 1% of sodium bicarbonate were added to rice porridge, increased reduction of OTA was observed as 78% and 68%, respectively. The same amounts of added sodium bicarbonate also further reduced OTA in oat porridge to 58% and 72%, respectively. In addition, increased reduction of OTA in the presence of fructose was observed. A combination of the two, i.e., 0.5% sodium bicarbonate and 0.5% fructose, resulted in a 79% and 67% reduction in rice porridge and oat porridge, respectively. These results indicate that indirect steaming may effectively reduce OTA in preparation of porridge-type products, particularly when sodium bicarbonate and/or fructose are added.
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