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971.
在25℃下分别测定正丙酸和正丁酸在苯相和纯水相中的分配比,以及在苯相和盐水溶液中的分配比,从而求出酸的活度系数。所用的盐有氯化锂、氯化钠、氯化钾、氯化锶、氯化钡、溴化锂、溴化钠、溴化钾等八种。对弱酸算出了未解离部分的活度系数。在所用盐浓度(0-1mol/l)范围内,作lgfu-Cs图,都呈直线。比较直线的斜率,对正丙酸为:SrCl2>BaCl2>LiCl≈NaCl>LiBr≈NaBr>KCl>KBr。对正了酸为:SrCl2>BaCl2>NaCl≈LiC1>NaBr≈KCl≈LiBr>KBr.指出小离子盐对小脂肪酸盐效应主要是静电力作用。 相似文献
972.
973.
Juan Huang Jian Wei Wang Tao Gong Zhi Rong Zhang *Key Laboratory of Drug Targeting Ministry of Education West China School of Pharmacy Sichuan University Chengdu China 《中国化学快报》2007,(3)
To enable insulin as multi-drug carrier, we designed and synthesized dendritic linker molecule bearing three 5-Fluorouracil residues at the branch ends. The new conjugate showed excellent water solubility. The stabilities under different conditions were investigated. The results showed that the conjugate was a potential prodrug to release free 5-Fu. 相似文献
974.
An accurate and reproducible method for the simultaneous determination of ampicillin (AMP), sulbactam (SUL), and cefoperazone (CFP) in pharmaceutical formulations by using HPLC with beta-CD stationary phase was developed. It involved the use of the added tetraethylammonium acetate (TEAA) reagent, pH, and methanol as the significant parameters to find the optimum separation condition. A high resolution and selectivity of analytes was obtained by running the mobile phase in methanol-5 mM TEAA buffer = 35:65 (v/v, pH 4.5) at 280 nm. The mean recoveries ranged from 96.6 to 103.3% for AMP in the synthetic mixture, 97.6 to 103.0% for SUL, and 97.0 to 104.0% for CFP. The low LOD (<1.8 microg/mL) and low CV (<0.9%) assured that this method was sensitive and reproducible. The assay of analytes in commercial products exhibited that it was convenient and reproducible for routine analyses of these components in sterilized H(2)O, saline, or 5% dextrose injection solutions. 相似文献
975.
Shu-ning Li Xin-lin Yang Wen-qiang Huang 《高分子科学》2007,(6):555-563
Narrow disperse poly(ethyleneglycol dimethacrylate-co-4-vinylpyridine)(poly(EGDMA-co-4-VPy))microspheres were prepared by distillation-precipitation copolymerization of ethyleneglycol dimethacrylate(EGDMA)and 4-vinylpyridine (4-VPy)with 2,2'-azobisisobutyronitrile(AIBN)as initiator in neat acetonitrile.The polymer microspheres containing pyridyl group were then utilized as stabilizer for gold metallic colloids with the diameter around 7 nm,which were prepared by the in situ reduction of gold chloride trihydrate with sodium borohydride through the coordination of the pyridyl group on the gel layer and surface of the microsphere with the gold metallic nano-particles.The catalytic properties of the pyridyl- functionalized microsphere-stabilized gold metallic colloids and the behavior of the stabilized-catalyst for the recycling were investigated with reduction of 4-nitrophenol to 4-aminophenol as a model reaction. 相似文献
976.
977.
Dispersive liquid-liquid microextraction (DLLME) coupled with high-performance liquid chromatography-variable wavelength detector (HPLC-VWD) was developed for extraction and determination of chloramphenicol (CAP) and thiamphenicol (THA) in honey. In this extraction method, 1.0 mL of acetonitrile (as dispersive solvent) containing 30 μL 1,1,2,2-tetrachloroethane (as extraction solution) was rapidly injected by syringe into a 5.00-mL water sample containing the analytes, thereby forming a cloudy solution. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by HPLC-VWD. Some important parameters, such as the nature and volume of extraction solvent and dispersive solvent, extraction time, sample solution pH, sample volume and salt effect were investigated and optimized. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 3 to 2000 μg kg−1 for target analytes. The enrichment factors for CAP and THA were 68.2 and 87.9, and the limits of detection (S/N = 3) were 0.6 and 0.1 μg kg−1, respectively. The relative standard deviations (RSDs) for the extraction of 10 μg kg−1 of CAP and THA were 4.3% and 6.2% (n = 6). The main advantages of DLLME-HPLC method are simplicity of operation, rapidity, low cost, high enrichment factor, high recovery, good repeatability and extraction solvent volume at microliter level. Honey samples were successfully analyzed using the proposed method. 相似文献
978.
通过将水合物的分解过程看作是无固态产物层生成的气固反应过程, 结合粒径缩小的收缩核反应模型和分形理论, 建立了多孔介质中水合物降压分解的分数维动力学模型, 提出了基于水合物分解实验数据计算多孔介质分形维数的方法. 分别利用前人的甲烷水合物和CO2水合物降压分解实验数据, 对上述分数维动力学模型进行了验证. 计算结果表明, 用提出的方法所计算得到的多孔介质分形维数与前人的测定结果基本符合; 对甲烷水合物和CO2水合物的降压分解过程, 提出的分数维动力学分解模型得出了和实验结果基本一致的预测, 绝对平均误差(AAD)小于10%. 相似文献
979.
980.
Deng J Hu XP Huang JD Yu SB Wang DY Duan ZC Zheng Z 《The Journal of organic chemistry》2008,73(15):6022-6024
A series of chiral beta-aryl-substituted gamma-amino butyric acid derivatives were synthesized in good enantioselectivities via the Cu-catalyzed asymmetric conjugate reduction of gamma-phthalimido-alpha,beta-unsaturated carboxylic acid esters using Cu(OAc)2 x H2O as a catalyst precursor, (S)-BINAP as a ligand, PMHS as a hydride source, and t-BuOH as an additive. The methodology has been applied successfully to the enantioselective synthesis of a chiral pharmaceutical, (R)-baclofen. 相似文献