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921.
Yogesh B. Pakade Ruchi Sharma Gireesh Nadda 《International Journal of Food Properties》2013,16(4):745-755
The single drop microextraction method was developed for the determination of ten organochlorine pesticides in tea brews using gas chromatograph-electron capture detector. The optimized parameters for effective extraction required a 2 μL drop of n-hexane at the tip of a microsyringe immersed in 5 mL of a diluted tea brew sample for 25 min and stirred at 600 rpm. The limit of detection in the range of 0.01 to 0.025 μg/L, with relative standard deviation of repeatability and reproducibility, was in the range of 1–10 and 8–24%. The relationship of the measured signal was a linear function (>0.9863) of concentration and the recovery method ranged from 92–116%. The single drop microextraction method showed the advantage of being easy to operate, low consumption of organic solvent, and high extraction efficiency. 相似文献
922.
D.J. MacLachlan 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(5):692-712
Data on the transfer of lipophilic xenobiotics from livestock feed and the environment to meat and milk are required for risk assessment purposes. Often, data are only available for lactating dairy cattle. Physiologically-based pharmacokinetic (PBPK) modeling has been used to explore differences between classes of food-producing animals. Blood and tissue levels of lipophilic xenobiotics under conditions approximating steady-state were simulated. Simulations of constant exposure were performed for lactating cows, non-lactating cattle, sheep, goats and swine. The tissue : blood partition coefficient, fat volume and fat blood flow were identified as critical determinants of predicted tissue concentrations. There may be significant breed differences in residues in milk and fat following exposure. Modeling was used to derive scaling factors that can be used to assist the extrapolation of transfer studies, carried out on lactating dairy cows, to other classes of cattle and different species. 相似文献
923.
To evaluate the potential public health risk of ethyl carbamate (EC), EC exposure from fermented foods and beverages for Hong Kong population was estimated. In 276 samples analysed, EC was detected (limit of detection (LOD) at 0.4?µg?kg?1) in 202 samples (73%), with higher levels in fermented red bean curd (150–650?µg?kg?1) and yellow wine (140–390?µg?kg?1), while low or non-detected (ND) in preserved vegetables (ND–10?µg?kg?1) and fermented tea (ND–15?µg?kg?1). The estimated dietary exposure from all fermented foods and beverages was 8.27?ng?kg?1?bw?day?1, while exposure excluding alcoholic beverages was 5.42?ng?kg?1?bw?day?1, with calculated margins of exposure (MOEs) at 3.6?×?104 and 5.5?×?104 respectively. The risk of adverse health effects was low for the average population but higher (MOE?of?103) for high consumers of alcoholic beverages especially habitual drinkers of alcoholic types with high EC contents. 相似文献
924.
ABSTRACTSome international organisations established maximum residue limits (MRLs) in food to protect human health. Mexico lacks regulations in this matter, affecting national and international trade from agroindustry. The aim of this study was to diagnose pesticide residues in oranges from Nuevo Leon, México, in citrus orchards. In May 2014, 100 orange fruit samples were taken randomly from orchards and subjected to analysis for 93 pesticides at residual level by GC/QQQ-MS and LCQ-TOF-MS. Results showed the presence of 15 pesticide residues in the samples. The comparison of the residual levels of pesticides found in orange samples among the MRLs allowed by USA, EU and Japanese regulations demonstrated that all samples were below MRLs issued by USA and Japan. Some orange samples were above MRLs issued by the EU. This provides a basis to establish strategies in order to satisfy International Standards to protect human health and encourage Food Safety in Mexico. 相似文献
925.
《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(6):980-989
ABSTRACTPesticide residues from the time of application until harvest were analysed for 20, 17 and 18 active insecticidal and fungicidal substances in Chinese cabbage, head cabbage and cauliflower, respectively. In total, 40 mathematical models of residue degradation were developed using a first-order kinetic equation, and from these models it was possible to forecast the action pre-harvest interval for a given action threshold for low-residue production in Brassica vegetables as a percentage of the maximum residue level. Additionally, it was possible to establish an action pre-harvest interval based on an action threshold of 0.01 mg kg?1 for the production of Brassica vegetables for baby food. Among the evaluated commodities, the speed of residue degradation was highest in head cabbage, medium in Chinese cabbage and lowest in cauliflower. The half-lives of pesticide in various vegetables were also determined: they ranged from 1.55 to 5.25 days in Chinese cabbage, from 0.47 to 6.54 days in head cabbage and from 1.88 to 7.22 days in cauliflower. 相似文献
926.
《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(12):2164-2172
ABSTRACTA novel carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) dispersive solid phase extraction (d-SPE) method combined with gas chromatography (GC) with an electron capture detector (ECD) was developed for the determination of seven pyrethroid pesticides in cucumber, spinach, eggplant, tomato and carrot. We optimised d-SPE conditions including the type and volume of the extractant, the type and amount of the sorbent, and shaking time. Under the optimal conditions, the linear range was from 2.0 to 2000 μg kg?1. The recoveries were from 88.5% to 108.2%, with the corresponding RSDs <6%, correlation coefficients 0.9987–0.9998, LOD 0.5–2.9 μg kg?1 and LOQ 1.5–9.7 μg kg?1. The proposed method is simple, fast, and safe, with high recovery and sensitivity, and is applicable to analysis of pyrethroid pesticides in vegetable samples. 相似文献
927.
The accumulation of citrulline and ornithine in wine or beer as a result of the arginine catabolism of some lactic acid bacteria (LAB) species increases the risk of ethyl carbamate and putrescine formation, respectively. Several LAB species, which are found as spoilage bacteria in alcoholic beverages, have been reported to be arginine degrading. This study evaluates the effect of ethanol content and low pH on the excretion of citrulline and ornithine by two strains belonging to the potential contaminant species Lactobacillus brevis and Pediococcus pentosaceus. In the conditions that most affected cell viability, arginine consumption per cell increased noticeably, indicating that arginine utilization may be a stress responsive mechanism. L. brevis showed a higher accumulation of ornithine in the media than P. pentosaceus. In the presence of ethanol, a higher expression of the arcC gene was found in P. pentosaceus, which resulted in a lower excretion of citrulline and ornithine than in L. brevis. This suggests that L. brevis is more likely to produce these amino acids, which are precursors of ethyl carbamate and putrescine. 相似文献
928.
Synthesis of dimethyl carbonate from methyl carbamate and methanol over lanthanum compounds 总被引:1,自引:0,他引:1
Dengfeng Wang Xuelan Zhang Yangyan Gao Fukui Xiao Yuhan Sun 《Fuel Processing Technology》2010,91(9):1081-1086
Various lanthanum compounds were used as the catalyst for the synthesis of dimethyl carbonate (DMC) from methyl carbamate and methanol. Among them, La(NO3)3 presented the best catalytic performance with the DMC yield of 53.7% under suitable reaction conditions. Based on the results of X-ray diffraction, Fourier transform infrared spectroscopy and element analysis, a possible reaction mechanism over lanthanum nitrate was proposed for this reaction. 相似文献
929.
河南煤业化工集团中原大化公司的尿素装置与三聚氰胺装置联产后,由于大量甲铵返回,造成系统的能耗和物耗大幅上涨。经过对系统进行分析和计算,制定了改造方案,进而实现了尿素装置高负荷、安全和经济的运行。 相似文献
930.