Determination of Ethyl Carbamate in Sake Using Headspace Solid Phase Microextraction

An analytical method for the determination of ethyl carbamate in alcoholic beverages has been developed and optimized. A combination of headspace solid phase microextraction (HS‐SPME), as the extraction technique, and GC/MS, as the determination technique, was utilized. Analytical grade ethyl carbamate dissolved in ethanol solution was analyzed to determine the optimum analytical conditions. Ethyl carbamate‐d₅ was added as an internal standard. The following HS‐SPME conditions were investigated: type of stationary phase of the fibre, ethanol content, sample volume and extraction time. The optimized procedure showed that the detection limit, relative standard deviation, and recovery were 6.7 μg/L, 0.4–2.0%, and 103.6–107.6%, respectively. The precision of this new method was equivalent to previous analyses. Finally, the developed method was applied to the analysis of ethyl carbamate in sake.     

Determination of ethyl carbamate in Chinese yellow rice wine using high‐performance liquid chromatography with fluorescence detection

Ethyl carbamate (EC) is a naturally occurring component in the fermented products, especially the Chinese yellow rice wine. EC has been found showing a potential for carcinogenity and causing food safety problems. This study is to investigate the application of the existing HPLC‐FLD method to the analysis of EC in Chinese yellow rice wine, and to validate it for EC analysis with high through‐out and applicability in Chinese yellow rice wine sample. The parameters examined in this study were fully evaluated. Results indicated that good linearity was obtained with a correlation coefficient exceeding 0.9990, the limit of detection and quantification was 73.2 and 243.9 μg L^?1, respectively. Recoveries ranged between 98.30% and 101.30%, and the precision of this method was lower than 5% (RSD). The method conducted in this work was successfully applied to determine EC concentration in Chinese yellow rice wine samples from different origins. The negative correlation between EC formation and urea level in yellow rice wine samples is evaluated with the developed HPLC‐FLD method.     

四甲基胍与离子液体协同催化合成苯氨基甲酸甲酯

将一系列咪唑类离子液体分别与四甲基胍(TMG)进行预混合制得一系列催化剂,于相同条件下考察了催化剂在苯胺(AN)与碳酸二甲酯(DMC)合成苯氨基甲酸甲酯(MPC)反应中的催化性能。结果表明,[bmim]BF_4([bmim]为1-丁基-3-甲基咪唑)与 TMG 混合制得的催化剂的活性最好。同时考察了催化剂制备条件对催化性能的影响,结果表明,在 m([bmim]BF_4):m(TMG)=2、20℃、60 min 的条件下制得的催化剂的性能最佳。优化了该催化剂合成 MPC 的反应条件,优化合成条件为n(DMC):n(AN)=3、170℃、3 h、催化剂用量为反应物总质量的15%,在此条件下,MPC 收率为46.0%,选择性为59.8%。将TMG 和[bmim]BF_4分别回收后,再制成催化剂循环使用,循环使用5次后,MPC 收率没有明显降低。     

改造系统实现尿素装置高负荷运行

重庆建峰化工股份有限公司三聚氰胺装置投产后由于大量甲铵液返回，造成尿素系统实际负荷增加到115％，尿素系统的分解和回收能力无法满足高负荷运行的要求，造成系统的能耗和物耗大幅上涨。经过对系统进行分析、计算，制定了扩能改造方案，进而实现了尿素装置高负荷、安全、经济的运行。     

Spatial Distributions of Legacy Contaminants in Sediments of Lakes Huron and Superior

The sediments of Lake Superior, Lake Huron, and Georgian Bay were sampled in 2001 and 2002 in order to evaluate the extent of surficial sediment contamination of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCs), polycyclic aromatic hydrocarbons (PAHs), and metals. Sediment concentrations of PCBs, OCs, PAHs, and mercury were generally low and up to 2 orders of magnitude less than in Lakes Erie and Ontario. In contrast, concentrations of metals such as arsenic, copper, and nickel were comparable to those in Lakes Erie and Ontario. These elevated Lakes Superior and Huron metal concentrations were attributed to naturally occurring metals within the bedrock, soil, and sediment of the study region. Concentrations of all contaminants were typically below the Canadian Sediment Quality Probable Effect Level (PEL) guidelines. With regard to spatial patterns, most contaminants were focused primarily in the depositional basins and atmospheric deposition was likely the major source of these chemicals to the lakes. The major exception was for metals (not including mercury) whose patterns were also influenced by natural sources as well as extensive mining activity. A comparison between surficial sediment contamination of samples collected as part of this survey and those collected in the late 1960s/early 1970s using similar methods showed that concentrations of DDT, PCB, lead, and mercury were generally similar between these two time periods. These results are not consistent with production and usage patterns that have declined substantially in the past 3 decades. We hypothesize that the lack of temporal trends is an artifact due to slow sediment accumulation rates as well as differences in analytical protocols between the two time periods.     

三种复配农药对甜菜夜蛾的防治效果

田间试验结果表明用复方B．T．轧剂150倍液．26％辛·灭乳油800倍液，50％辛·氰乳油800倍液，防治甜菜夜蛾．药后5～7天平均校正防治效果均达86％以上。     

Benzene‐di‐N‐substituted carbamates as conformationally constrained analogs of Pseudomonas lipase substrates

Benzene‐1,2‐, ‐1,3‐, and ‐1,4‐di‐N‐substituted carbamates ( 1 – 15 ) are synthesized as the constrained analogs of gauche, eclipsed, and anti conformations of diesters of ethylene glycol, respectively. Carbamates 1 – 15 are characterized as the pseudo‐substrate inhibitors of Pseudomonas species lipase. Long‐chain carbamates are more potent inhibitors than short‐chain ones. Different geometries of benzene‐di‐substituted carbamates, such as benzene‐1,2‐di‐N‐octylcarbamate ( 3 ) (ortho compound), benzene‐1,3‐di‐N‐octylcarbamate ( 8 ) (meta compound), and benzene‐1,4‐di‐N‐octylcarbamate ( 13 ) (para compound), show similar inhibitory potencies for the enzyme. In other words, kinetic data suggest that the enzyme does not discriminate ortho, meta, and para geometries of these constrained analogs.     

Determination of organochlorine and pyrethroid pesticides in fruit and vegetables using SAX/PSA clean-up column

A study was conducted to investigate the organochlorine and pyrethroid pesticide residues in fruit and vegetables from market in Malaysia. Gas chromatography with electron capture detector (GC-ECD) was used to determine the concentrations of pesticide residues and SAX/PSA was used as a clean-up. Cypermethrin was detected in 38 of 302 vegetable samples with a mean value of 0.47 mg/kg. The mean value of cypermethrin for tomato, chinese parsley, chinese celery, chilli, brinjal, french beans, green mustard and capsicum ranged from 0.16 to 1.48 mg/kg. The mean values for all samples were below the maximum residue limits (MRLs) allowed by the Malaysian Food Regulations except for brinjal. None of the 206 fruit samples tested showed any pesticide residue.     

Contaminants in organically and conventionally produced winter wheat (Triticum aestivum) in Belgium

A database has been compiled with the levels of important contaminants (mycotoxins, heavy metals and pesticides) measured from 2002 to 2005 in winter wheat (Triticum aestivum) grown in Belgium according to the organic and conventional farming systems. Assuming no further change in contaminant levels during cereal processing and during the preparation of foodstuffs, conservative intakes are estimated for the consumers of cereal-based products such as flour, bread, breakfast cereals, dough and pastry. The results show that for the consumer of organic foodstuffs, estimated daily intakes are 0.56 µg deoxynivalenol (DON), 0.03 µg zearalenone (ZEA), 0.19 µg Cd, 0.28 µg Pb and 0.0006 µg Hg kg^-1 body weight, taking into account the average contaminant levels in unprocessed grains and the average cereal products consumptions in Belgium. For the consumers of conventional foodstuffs, the corresponding estimated daily intakes are 0.99 µg DON, 0.06 µg ZEA, 0.17 µg Cd, 0.12 µg Pb and 0.0007 µg Hg kg^-1 body weight. In addition, it appears that for the consumers of conventional products, intakes of some post-harvest insecticides have to be taken into account (0.11 µg chlorpyriphos-methyl, 0.2 µg dichlorvos and 0.24 µg pirimiphos-methyl kg^-1 bw). When expressed as a percentage of the tolerable/acceptable daily intake (TDI/ADI), it seems that the corresponding estimated (conservative) intakes are the highest for DON (56% for organic and 99% for conventional cereal products), ZEA (16% for organic and 32% for conventional cereal products), and Cd (19% for organic and 17% for conventional cereal products), all other estimated intakes of contaminants (including pesticides) being lower than 10% of the TDI/ADI.     

Photocatalytic degradation of organophosphorus pesticides using floating photocatalyst TiO2 · SiO2/beads by sunlight

In this paper, the floating TiO₂ · SiO₂ photocatalyst beads are prepared by the dip-coating method, which use hollow glass microbeads as the carrier and titanium tetraisopropoxide [Ti(iso-OC₃H₇)₄] and ethyl silicate as the raw materials. The feasibility of photocatalytic degradation of organophosphorus pesticides using TiO₂ · SiO₂ beads as a floating photocatalyst by sunlight is studied. The results show that the best heat treatment condition for TiO₂ · SiO₂ beads is at 650 °C for 5 h. Apart from heat treatment temperature and time, the amount of SiO₂ also influences the photocatalytic activity of TiO₂ · SiO₂ beads. The optimum amount of SiO₂ is 0.20 (molecular fraction). 0.65 × 10⁻⁴ mol/dm³ of four organophosphorus pesticides of three structures can be completely photocatalytically degraded into after 420 min illumination by sunlight. The effects of parameters such as the amount of TiO₂ · SiO₂ beads, initial pH and metal ions on the photocatalytic degradation of the organophosphorus pesticides are also studied. The possible mechanisms of photocatalytic degradation of phosphate ester pesticides are proposed. After 120 h illumination by sunlight, there is no significant loss of the photocatalytic activity of TiO₂ · SiO₂ beads.