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31.
A method is described for the determination of aldicarb and its metabolites (the sulphoxide and sulphone) in urine by gas chromatography with flame photometric detection (GC-FPD). The sample was concentrated with a column containing activated charcoal and Florisil, and then eluted with dichloromethane-acetone (1:1, v/v). The aldicarb and aldicarb sulphoxide in the eluate solution were oxidized to aldicarb sulphone and the total sulphone concentration was determined by GC-FPD after extraction with dichloromethane and clean-up with an activated charcoal column. The detection limit was 0.0024 mg/l. The mean recoveries from spiked urine in the range 0.04-0.12 mg/l were 90.9%, 86.6%, 92.6% for aldicarb, aldicarb sulphoxide and aldicarb sulphone, respectively. 相似文献
32.
Chiral quaternary ammonium salts derived from cinchonidine have been applied to catalyze the stereoselective iodolactonizations of trans-5-aryl-4-pentenoic acids leading to a mixture of two regioselectively iodolactonized products with fair to excellent yield (37-98%) and moderate enantioselectivity (exo = 42.0% ee, endo = 31.0% ee) under mild conditions. This work is the first example of asymmetric iodolactonization reaction in the presence of less than a stoichiometric amount of chiral reagent. 相似文献
33.
聚羟基丁酯酯缓释微球的制备及性能 总被引:6,自引:1,他引:6
用溶剂蒸发法制备了以新型生物可降解材料聚羟基丁酸酯为载体、以安定为模药的缓释微球,讨论了药物与载体之比对药物含量与包封率的影响,以及制备微球条件对药物释放性能的影响;微球平均粒径为30~40μm,粒径分布在1~1.5之间,最大载药量为19.51%;最高包封率为67.11%;体外累积释放曲线呈“两相”释放特征并拌随初始的“突释效应”。扫描电镜观察微球表面呈皱缩表观形态结构,微球内部横断面具有孔道与孔 相似文献
34.
Proton transfer along a single-file hydrogen-bonded water chain is elucidated with a special emphasis on the investigation of chain length, side water, and solvent effects, as well as the temperature and pressure dependences. The number of water molecules in the chain varies from one to nine. The proton can be transported to the acceptor fragment through the single-file hydrogen-bonded water wire which contains at most five water molecules. If the number of water molecule is more than five, the proton is trapped by the chain in the hydroxyl-centered H(7)O(3) (+) state. The farthest water molecule involved in the formation of H(7)O(3) (+) is the fifth one away from the donor fragment. These phenomena reappear in the molecular dynamics simulations. The energy of the system is reduced along with the proton conduction. The proton transfer mechanism can be altered by excess proton. The augmentation of the solvent dielectric constant weakens the stability of the system, but favors the proton transfer. NMR spin-spin coupling constants can be used as a criterion in judging whether the proton is transferred or not. The enhancement of temperature increases the thermal motion of the molecule, augments the internal energy of the system, and favors the proton transfer. The lengthening of the water wire increases the entropy of the system, concomitantly, the temperature dependence of the Gibbs free energy increases. The most favorable condition for the proton transfer along the H-bonded water wire is the four-water contained chain with side water attached near to the acceptor fragment in polar solvent under higher temperature. 相似文献
35.
低分子量溴代聚苯乙烯的制备及应用 总被引:5,自引:0,他引:5
用溶液法合成了一系列低分子量的聚苯乙烯,其溴化产物(Br-PS)的溴含量和热稳定性与美国同类产品Pyro-Chek LM相当,分别用作聚苯乙烯树脂的阻燃剂,极限氧指数测定结果表明,其阻燃性也达到了Pyro-Chek LM的水平。 相似文献
36.
Jiang Ke QIN Xian Zhang BU Yu Fang WANG Zhi Yun DU Xing Yuan WANG Zhi Shu HUANG Lin MA Lin Kun AN Lian Quan GU 《中国化学快报》2005,16(11):1451-1454
The reactions of tanshinone IIA with aromatic aldehydes have been investigated and several 2, T-(substituted arylmethylene) bis (1,6,6-trimethyl-6,7,8,9-tetrahydrophenanthro[1,2-b]- furan- 10, 11-dione) derivatives were obtained, 相似文献
37.
Yunhui Zhai Xijun Chang Yuemei Cui Ning Lian Shoujun Lai Hong Zhen Qun He 《Mikrochimica acta》2006,154(3-4):253-259
A rapid, selective method that utilize 4-(2-Pyridylazo)-resorcinol (PAR)-modified nanometer SiO2 (nanometer SiO2–PAR) as a new solid-phase extractant for preconcentration of trace mercury (II) has been developed. The adsorption property
of nanometer SiO2–PAR for metal ions was studied by selectively extracting different metal ions from aqueous solutions. The results revealed
an excellent affinity of the nanometer SiO2–PAR for mercury (II) in presence of interfering metal ions at pH 4. The main parameters of solid-phase extraction such as
shaking time, elution and sample dilution effect were studied. The extractant shows rapid kinetic sorption, and the adsorption
equilibrium of mercury (II) on nanometer SiO2–PAR was achieved in less than 2 min. The adsorbed mercury (II) was easily eluted by 4 mL of 6 mol L−1 HCl. The maximum preconcentration factor was 50. The maximum static adsorption capacity was 276 μmol g−1 at pH 4. The detection limit (3σ) was 0.43 μg L−1 for cold vapor atomic absorption spectrometry (CVAAS), and the relative standard deviation of the eight replicate determinations
was 2.4% for the determination of 2.0 μg of Hg(II) in 100 mL water sample. The method was applied to the determination of
trace mercury (II) in sample solutions with satisfactory results. 相似文献
38.
Chen L Jiang F Lin Z Zhou Y Yue C Hong M 《Journal of the American Chemical Society》2005,127(24):8588-8589
A blue luminescent tetradecavanadate compound, [Et4N]5[V14O36Cl], has been synthesized. It possesses an unprecedented half-open basket framework. Through the {ABAB}-type stacking, the {V14O36} clusters form infinite one-dimensional channels with considerable accessible volume in the crystalline state. 相似文献
39.
40.
研究了Cu(Ⅱ)-胱氨酸络合物极谱波的性质;提出了一种用示波极谱法测定蛋白质中胱氨酸的新方法,可在8.0×10~(-4)mol/L Cu~(2+)+8.0×10~(-3)mol/L三乙醇胺的溶液中测定0.05~20mg/L的胱氨酸。 相似文献