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71.
Reversed‐phase liquid chromatography with electrospray mass detection and 1H and 13C NMR characterization of new process‐related impurities,including forced degradants of Efavirenz: Related substances correlated to the synthetic pathway 下载免费PDF全文
In this study, a stability‐indicating reversed‐phase liquid chromatographic electrospray mass spectrometric method was developed and validated for the determination of process‐related impurities and forced degradants of Efavirenz in bulk drugs. Efavirenz was subjected to acid, alkaline hydrolysis, H2O2 oxidation, photolysis, and thermal stress. Significant degradation was observed during alkaline hydrolysis, and the degradants were isolated on a mass‐based purification system and characterized by high‐resolution mass spectrometry, positive electrospray ionization tandem mass spectrometry, and 1H and 13C NMR spectroscopy. Accurate mass measurement and NMR spectroscopy revealed the possible structure of process‐related impurities and degradant under stress conditions. The acceptable separation was accomplished on Waters bondapak C18 column (250 mm × 4.6 mm; 5 μm), using 5 mM ammonium acetate and acetonitrile as a mobile phase in a gradient elution mode at a flow rate of 1.0 mL/min. The eluents were monitored by diode array detector at 247 nm and quantitation limits were obtained in the range of 0.1–2.5 μg/mL for Efavirenz, degradants, and process‐related impurities. The liquid chromatography method was validated with respect to accuracy, precision, linearity, robustness, and limits of detection and quantification as per International Conference on Harmonization guidelines. 相似文献
72.
An improved and practical synthesis of enzalutamide was accomplished in five steps. Starting from 4-bromo-2-fluoro-benzonic acid, a methyl esterification, Ullmann ligation, methyl esterification, ring closing reaction and final methyl amidation provided the target in 35% total yield with 99.8% purity. Five identified impurities were also synthesized. This efficient and economical procedure avoids the use of highly toxic reagents and multiple recrystallization operations, which is suitable for further industrialization. 相似文献
73.
ICP-A ES法测定中国不同产地绒柄牛肝菌中矿质元素含量 总被引:2,自引:0,他引:2
采用微波消解处理样品,以电感耦合等离子体发射光谱法(IC P-A ES )测定了采自云南省不同地点的绒柄牛肝菌菌盖和菌柄中的12种矿物质元素(P ,Na ,Ca ,Cu ,Fe ,Mg ,Zn ,As ,Cd ,Co ,Cr ,Ni)含量。结果显示:绒柄牛肝菌中P ,Ca ,Mg ,Fe ,Zn ,Cu的含量较高,其中菌盖中的P ,Mg ,Zn ,Cd较高,而菌柄中的Ca ,Co ,Ni较高;聚类分析结果显示,采用普洱地区的样品与其他地区的样品差异较大;主成分分析结果显示,前三个主成分的累计贡献率为77%,其中第一主成分中的P ,Ca ,Cu ,Fe ,Mg ,As ,第二主成分中的Ni ,Na以及第三主成分中的Cd和Zn对区分不同地点的样品贡献较大。结果表明采自不同生境地的食用菌元素含量差异较大。 相似文献
74.
给出强Z-连续domain和Z-代数domain的一个刻画及一个范畴性质--余反射性质. 相似文献
75.
A simple and sensitive high performance liquid chromatography (HPLC) method was developed to determine residual Pluronic F-68 (PF-68) in in-process samples of monoclonal antibody (MAb) preparations. The method permits the direct injection of proteinaceous samples after simple sample dilution and is able to quantitate as low as 50 mg/L of PF-68 in the presence of up to approximately 30 g/L of protein. The PF-68 molecule was separated on a restricted access reversed phase column using a step gradient and then measured by an evaporative light scattering detector (ELSD). The method was successfully applied to demonstrate PF-68 clearance in MAb purification processes. A modified colorimetric method using liquid-liquid extraction and cobalt thiocyanate to derivatize PF-68 is also described. The results obtained by both the HPLC and colorimetric methods were compared. In addition to its ease of use and simplicity, the HPLC method had better accuracy and higher throughput than the colorimetric method. 相似文献
76.
M. Hofheinz X. Jehl M. Sanquer G. Molas M. Vinet S. Deleonibus 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(3):299-307
We study anomalies in the Coulomb blockade spectrum of a quantum dot
formed in a silicon nanowire. These anomalies are attributed to electrostatic
interaction with charge traps in the device. A simple model reproduces these
anomalies accurately and we show how the capacitance matrices of the traps can
be obtained from the shape of the anomalies. From these capacitance matrices
we deduce that the traps are located near or inside the wire. Based on the
occurrence of the anomalies in wires with different doping levels we infer
that most of the traps are arsenic dopant states. In some cases the anomalies
are accompanied by a random telegraph signal which allows time resolved
monitoring of the occupation of the trap. The spin of the trap states is
determined via the Zeeman shift. 相似文献
77.
78.
ICP-AES测定米中多种微量元素 总被引:1,自引:0,他引:1
以全谱直读光谱法测定了米中11种微量元素。对米的消化方法、元素分析谱线的选择、背景校正、仪器分析参数等因素进行了研究,综合确定了最佳试验条件。试验表明测定元素的回收率在96%—109%之间。 相似文献
79.
文中叙述了HL-1M托卡马克硼化真空紫外光谱区杂质辐射的观测结果。分析得出:硼化有效地控制等离子体中的杂质,其中,氧杂质减少约65%,碳杂质减少约60%,金属杂质减少约85%。 相似文献
80.
A finite element method for solution of the stream function formulation of Stokes flow is developed. The method involves complete cubic non-conforming (C0) triangular Hermite elements. This element fails the patch test. To correct the element and produce a convergent method we employ a penalty method to weakly enforce the desired continuity constraint on the normal derivative across the inter-element boundaries. Successful use of the method is demonstrated to require reduced integration of the inter-element penalty with a 1-point Gauss rule. Error estimates relate the optimal choice of penalty parameter to mesh size and are corroborated by numerical convergence studies. The need for reduced integration is interpreted using rank relations for an associated hybrid method. 相似文献