Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Development and validation of a chromatographic method for determining Clematichinenoside AR and related impurities
Yang Zhou, Yue Guan, Ji Shi, Xiaolin Zhang, Lan Yao, Lifang Liu
Chemistry Central Journal , 2012, DOI: 10.1186/1752-153x-6-150
Abstract: A simple and stability indicating RP-HPLC method was developed and validated for determining the purity of clematichinenoside AR (AR), a natural product from the roots of Clematis manshurica Rupr. (Ranunculaceae) with the potential of treating rheumatoid arthritis. Five impurities were characterized, and impurity 2 (Clematomandshurica saponin F) is a new triterpenoid saponin isolated from this product. Optimum separation for clematichinenoside AR and five related impurities was carried out on an Agilent octadecylsilane bonded silica gel column (TC-C18, 4.6 mm ×150 mm, 5 μm) using a gradient HPLC method. The validation results showed good sensitivity, specificity, linearity(r2>0.9992) precision(RSD<1.63%), accuracy(recoveries in the range of 95.60%-104.76%) and robustness. Three AR bulk samples containing all the impurities were examined by two methods, and the stability of correction factors for the determination of related impurities was discussed. The proposed stability-indicating method was suitable for the quality control of this natural product.Five related impurities of clematichinenoside AR were characterized, including a new triterpenoid saponins firstly found in clematichinenoside AR bulk samples. In the simple chromatographic method for determining clematichinenoside AR and its related impurities in bulk samples, the correction factor was better for the quality control in the relative stable concentrations.Radix et Rhizoma Clematidis (Wei-Ling-Xian) has been used as an anti-inflammatory, antitumor, and analgesic agent in traditional Chinese medicine (TCM) with a long history [1,2]. Triterpenoid saponins are considered to be the main bioactive constituents in the root extracts of clematis species, and recent pharmacological studies revealed that some triterpenoid saponins have significant anti-inflammatory, antitumor and analgesic activities [3-7]. Clematichinenoside AR, 3-O-β-[(O-α-L-rhamnopyranosyl-(1→6)-O-β-D-glucopyranosyl-(1→4)-O-β-D-glu-copyranosyl-(1
涡流波痕  [PDF]
海洋科学 , 1987,
Abstract: 本文介绍一种新的波痕类型——涡流波痕,它由若干列放射状排列的波痕组成一个小波痕体系。单列波痕脊的中段呈弧形前凸。笔者将涡流波痕的形态特征与涡流的运动特征相比较,探讨了形成涡流波痕的水动力条件。笔者在阐明涡流波痕产地地理背景的基础上,指出大潮差沙滩的后滨是发育涡流波痕的理想环境。
Physicochemical factors governing the partition of pramipexole and its five impurities in microemulsion liquid chromatographic systems
Vemi?, Ana M.;Malenovi?, An?elija M.;Raki?, Tijana M.;Kosti?, Na?a M.;Jan?i?-Stojanovi?, Biljana S.;Ivanovi?, Darko P.;Medenica, Mirjana B.;
Journal of the Brazilian Chemical Society , 2012, DOI: 10.1590/S0103-50532012005000079
Abstract: microemulsions when used as mobile phases represent a very powerful chromatographic tool due to their polyphase structure. the aim of this study was to investigate the influence of the mobile phase composition and resulting microemulsion droplet's properties, as well as the stationary phase lipophilicity on the chromatographic behavior of pramipexole and its five impurities. investigation was carried out according to the experimental plan defined by a full factorial design 24 with four central point replications. while the most affected by column characteristics was the last eluting, most lipophilic substance, the composition and characteristics of microemulsion droplets were equally important, so the partition system microemulsion droplets/stationary phase proved to be the most significant. stationary phase lipophilicity did not affect the most hydrophilic component and only the partition system microemulsion droplets/bulk of the eluent impacted its behavior. for the separation of the critical pair, almost equal effects of the microemulsion droplets/stationary phase and bulk of the eluent/stationary phase partition systems were noted.
Development of validated stability-indicating chromatographic method for the determination of fexofenadine hydrochloride and its related impurities in pharmaceutical tablets
Hadir M Maher, Maha A Sultan, Ileana V Olah
Chemistry Central Journal , 2011, DOI: 10.1186/1752-153x-5-76
Abstract: Fexofenadine, α, α-dimethyl-4-[1-hydroxy-4-[4-(hydroxydiphenyl-methyl)-1-piperidinyl] butyl]-benzene acetic acid [1] (Figure 1) is the active carboxylic acid analogue of the antihistamine terfenadine. It shares the histamine H1 receptor antagonist and non-sedative properties of the parent compound. This could be attributed to its capability to exist in zwitter-ionic form so it cannot pass through blood-brain barrier and therefore does not cause sedation [2,3]. Fexofenadine is a second generation antihistamine drug useful to available treatments of allergic diseases with a wide margin of safety [4,5]. FEX displays some anti-inflammatory properties and it has also another advantage as it lacks the cardiotoxic side effects (fatal arrhythmia) associated with terfenadine [2,3]. FEX is rapidly absorbed with a long duration of action, making it suitable for once daily administration. Thus, it fulfils the essential and desirable characteristics of an ideal antihistamine, being responsible for the improvement in quality of life of the patients with allergic diseases [4,6].There are several reports on liquid chromatographic determination of FEX in biological fluids. Among which are those using LC-MS/MS [7], ultraviolet detection [8] and fluorescence detection [9]. Few methods reported the quantitation of FEX in pharmaceutical dosage forms using spectrophotometric methods [10], LC methods with ultraviolet detection [11-13], and capillary electrophoresis [14,15].It is reported in the BP that four main impurities may be encountered along with FEX (para isomer). These impurities are; impurity A (keto fexofenadine), impurity B (meta-isomer of FEX), impurity C (methyl ester of fexofenadine) and D (methyl ester of keto fexofenadine), Figure 1[16]. The BP describes two separate HPLC methods for the determination of FEX and its four related impurities. The first one utilizes β-cyclodextrin modified silica (silica gel BC for chiral chromatography R1) to test for impurity B while the ot
Acrylamide and Its Presence in Foods  [cached]
Alper Karagoz
TAF Preventive Medicine Bulletin , 2009,
Abstract: Acrylamide is chemical matter which forms spontaneously as frying or cooking heat treatment enforced in foods. Though the said chemical is widely found in the fried or oven-cooked foods, it can also exist in the grilled foods prepared at homes or at large restaurants. However, no acrylamide has been found in the raw or boiled foods. Based on the studies made on acrylamide, and its observed biological effects, that chemical is suspected to be a human carcinogen. Neural destructions have been observed on the individuals who are exposed to this chemical. As yet, there isn t any direct evidence about carcinogenic effects of acrylamide for human. In conclusion, we can say that acrylamide creates a risk for human health only in the cases of long term exposure to it. [TAF Prev Med Bull. 2009; 8(2): 187-192]
Application of solid phase extraction disk in the determination of acrylamide in tap water

ZHANG Bo,QI Yue,GAO Henan,BAO James Jianmin,

色谱 , 2010,
Abstract: A simple and fast method of solid phase extraction (SPE) disk for the determination of trace acrylamide was developed. Using this new technique along with high performance liquid chromatography (HPLC) and ultraviolet spectroscopy (UV) detection, the feasibility of SPE disk method for rapid enrichment was demonstrated in the determination of trace acrylamide in 500 mL tap water. Active carbon was chosen as the adsorbent to be incorporated into the SPE disk as it gave the best adsorption efficiency. Experimental parameters including solvent, elution volume, elution rate, breakthrough volume were optimized to give the highest efficiency of extraction. Under proper chromatographic conditions, acrylamide was easily separated from other impurities. A linear relationship between peak area and mass concentration in the range 0.05~0.5mg/L of acrylamide was established with a correlation coefficient of 0.998. The limit of detection was 20 ng/L. The recoveries for acrylamide with different concentrations and volumes ranged from 94.12% to 100.2%. The relative standard deviations (RSDs) were 2.09%~4.51% (n=3). The recovery for acrylamide spiked into a tap water sample was 79.96%. The method is simple, fast, sensitive and suitable for the determination of acrylamide in tap water.
人牙咬痕模拟系统的建立及应用  [PDF]
复旦学报(医学版) , 2009,
Abstract: 目的建立人牙咬痕模拟系统并对其进行效果评价。方法自制人牙咬痕模拟系统,运用该系统在活体乳猪腹部形成咬痕,记录咬痕并进行效果评价。结果本研究成功建立了人牙咬痕模拟系统,应用30kgN的力加载于乳猪腹部皮肤所形成的咬痕形态较清晰,持续时间较长。结论人牙咬痕模拟系统的建立为后续的咬痕实验室研究及咬痕的同一认定提供了条件。
Neurotoxicity of Acrylamide in Exposed Workers  [PDF]
Manuela Pennisi,Giulia Malaguarnera,Valentina Puglisi,Luisa Vinciguerra,Marco Vacante,Mariano Malaguarnera
International Journal of Environmental Research and Public Health , 2013, DOI: 10.3390/ijerph10093843
Abstract: Acrylamide (ACR) is a water-soluble chemical used in different industrial and laboratory processes. ACR monomer is neurotoxic in humans and laboratory animals. Subchronic exposure to this chemical causes neuropathies, hands and feet numbness, gait abnormalities, muscle weakness, ataxia, skin and in some cases, cerebellar alterations. ACR neurotoxicity involves mostly the peripheral but also the central nervous system, because of damage to the nerve terminal through membrane fusion mechanisms and tubulovescicular alterations. Nevertheless, the exact action mechanism is not completely elucidated. In this paper we have reviewed the current literature on its neurotoxicity connected to work-related ACR exposure. We have analyzed not only the different pathogenetic hypotheses focusing on possible neuropathological targets, but also the critical behavior of ACR poisoning. In addition we have evaluated the ACR-exposed workers case studies. Despite all the amount of work which have being carried out on this topic more studies are necessary to fully understand the pathogenetic mechanisms, in order to propose suitable therapies.
化石波痕和现代波痕的对比研究——以大连震旦系石英岩波痕为例  [PDF]
沉积学报 , 1990,
Abstract: 研究波痕的重要意义,在于鉴定地层是否倒转,以确定区域地层层序。大连白云山发现在同一石英岩层内,正倒波痕共存,莫衷一是。根据北戴河海滩现代波痕的观察,即棱角明显正位分明已成型的涨潮痕,但在退潮时,因水动力条件和地形关系可以被改造,从而造成混淆。本文提出了鉴定方法。
拉丁方合痕分类的快速算法  [PDF]
北京邮电大学学报 , 2001,
Abstract: 提出了一种拉丁方合痕分类的快速算法,该算法结构简单,复杂度低.利用该算法,对n阶拉丁方(n<9)进行了合痕分类.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.