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Sharon Hongxia Guan Michelle Wenlin Huang Xiaoping Li Qingsong Cai 《Analytical letters》2018,51(4):613-625
Four commonly found pesticides (alachlor, atrazine, metolachlor, and simazine) in surface water were determined using dispersive pipette extraction followed by gas chromatography–mass spectrometry. The rapid mixing and equilibrium between the dispersive pipette extraction adsorbent and water sample resulted in fast and efficient extraction. Using only 5?mL of water sample, the estimated time consumption for extraction of each sample was less than 5?min. Method validation was performed to evaluate accuracy, precision, linearity, the limits of detection, and the limits of quantitation. Average recovery of above 90% was obtained with relative standard deviations below 10%, which indicated good accuracy and precision of the dispersive pipette extraction method. Coefficients of determination were all above 0.9901 and showed good linearity. For the four pesticides studied using the current method, the limits of detection ranged from 7 to 40?ng?L?1, and limits of quantitation were from 20 to 130?ng?L?1. Method validation results supported the application of the current method for drinking water safety monitoring per National Primary Drinking Water Regulations established by the US Environmental Protection Agency. Water samples from Lake Lanier and Stone Mountain Lake (Georgia, USS) were analyzed with this method as a preliminary work for a larger scale drinking water quality study in the future. Trace amounts of simazine and atrazine were found in lake water samples, but both were below the regulation levels of the US Environmental Protection Agency. 相似文献
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添加剂对高碱煤钠迁移和灰分烧结温度的影响 《燃料化学学报》2018,46(11):1298-1304
选取三种不同的添加剂(高岭土、SiO2和Al2O3),研究它们对高碱准东煤钠迁移和灰分烧结温度的影响,并且添加比例为1%-5%。结果表明,三种添加剂的钠捕集效率依次为:高岭土 > SiO2 > Al2O3。钠捕集效率随着添加比例的增加而升高,但受温度影响比较复杂。高岭土的钠捕集效率在600-1000℃先增加后减小,并在900℃达到最大值,其余两种随温度的升高均减小。准东煤灰的烧结温度为803℃,添加高岭土后,烧结温度随添加比例的增加先降低后上升。当添加比例为3%时,因为钙长石和钙黄长石的低温共熔反应而达到最小值。SiO2的添加比例为5%时,由于透辉石的生成和SiO2本身的"骨架"作用,烧结温度迅速升高到879℃。Al2O3对烧结温度的影响最小。 相似文献
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Treatment of the labile cluster 1,2-Os3(CO)10(MeCN)2 (1) with the diphosphine ligand 2,3-bis(diphenylphosphino)quinoxaline (dppq) at room temperature affords 1,2-Os3(CO)10(dppq) (2b) as the kinetic product of ligand substitution in 84% yield. 2b isomerizes to the thermodynamically more stable dppq-chelated cluster 1,1-Os3(CO)10(dppq) (2c) as the sole observable product under CO at temperatures below 358 K. The kinetics for the conversion of 2b → 2c have been investigated by NMR spectroscopy in CDCl3 over the temperature range 323-353 K, and the reaction was found to exhibit a rate law that is first order in 2b. The calculated activation parameters [ΔH≠ = 25.4(4) kcal/mol; ΔS≠ = −3(1) eu] support an intramolecular isomerization scenario, one that involves the migration of phosphine and CO groups about the cluster polyhedron. The disposition of the dppq ligand in the isomeric Os3(CO)10(dppq) clusters has been established by X-ray crystallography and 31P NMR spectroscopy. Photolysis of 2c at 366 nm leads to CO loss and ortho metalation of one of the aryl groups on the Ph2P moiety to furnish the hydride cluster HOs3(CO)9[μ-PhP(η1-C6H4)(Ph2P)quinoxaline] (3). The isomerization behavior exhibited by 2b follows that of related diphosphine-substituted Os3 clusters prepared by us. 相似文献
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An electrically heated microelectrode chip (HMEC) was designed and the Ru(bpy)32+/carbofuran electrochemiluminescence (ECL) systems were applied to characterize the performance of the HMEC. The ECL intensities increase at elevated electrode temperature, and the detection limit at 60°C (electrode surface temperature) was about 10 times lower than that at 30°C. The results indicate that new heated electrode can be handled easily and can be mass produced, the difference between the electrodes was little. The stability of the HMEC was good since the electrode surface can hardly be destroyed during detection and storage. 相似文献
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采用溶胶-凝胶法制备了不同烧结温度的钙钛矿类锰氧化物La0.67Sr0.33MnO3样品。实验结果表明,在1573 K以上烧结的样品,晶粒出现异常长大,晶界效应明显。随着烧结温度的提高,磁化强度逐渐增大,但样品的居里温度基本不变。此外,在1173和1573 K温度下烧结的样品,均出现了低于居里温度的金属-半导体导电行为转变。在合适的烧结条件下,可以观察到隧道磁电阻(TMR)和超大磁电阻(CMR)2种磁电阻效应。实验表明,自旋电子的输运,不仅与样品平均粒径的大小和密度有关,而且与晶界的微观结构有密切关系。 相似文献
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LI Chun-Bao Chen Yi LI Song-Lin ZHANG Wen-Qin CUI Yi JI Xiu-Jie ZHENG Peng-Wu 《结构化学》2002,21(5):470-472
1 INTRODUCTION (9S,13R,14S)-7,8-Didehydro-3,7-dimethoxy-4-hydroxy-17-methylmorphinan-6-one I is an impor- tant natural product that was used to ease pain, decrease blood pressure and diminish inflammation. In order to study the stereochemistry of the reduction of I with potassium boronhydride, the crystal structure of the title compound II was determined by X-ray diffraction method. 2 EXPERIMENTAL 2. 1 Instrument The melting point was measured on a Yanagimoto MP-500 apparatus… 相似文献
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