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Important improvements have recently been made on the elution by characteristic point (ECP) method to increase the accuracy of the determined adsorption isotherms. However, the method has so far been limited/used for only type I adsorption isotherms (e.g. Langmuir, Tóth, bi-Langmuir). In this study, general strategies are developed to expand the ECP method for the determination of more complex adsorption isotherms including such containing inflection points. We will exemplify the methodology with type II, type III and type V isotherms. Guidelines are given for how to determine such isotherms using the ECP method and for the experimental considerations that must be taken into account or that may be eliminated in the particular case. 相似文献
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Ablajan K 《Journal of mass spectrometry : JMS》2011,46(1):77-84
Isoflavone mono‐O‐glycosides were investigated by electrospray ionization tandem mass spectrometry with a quadrupole linear ion trap mass spectrometer in negative ion mode. Isoflavonoids having different positions of glycosylation or methylation were differentiated according to the relative abundances of Y0? and [Y0? H]?? ions generated from the [M ? H]? ion. It is found that the site of glycosyl or methyl group significantly affects relative abundances of the Y0? and [Y0? H]?? ions. In addition, the characteristic ion [Y0? 2H]? was observed in the product ion spectrum of genistein 7‐O‐β‐D ‐glucoside and was also detected, together with the [Y0? CH3]?? and [Y0? H ? CH3]? ions in the product ion spectra of glycitin and 6‐methoxy genistein 7‐O‐β‐D ‐glucoside. The structures of isoflavonoids can be characterized and identified according to the formation of these diagnostic ions. The results obtained from this investigation can promote the rapid identification of isoflavonoids in crude plant extracts. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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以市场上销售的国内改色紫红色圆刻面型钻石为研究对象,通过对其光谱学特征进行分析,确定了此类紫红色改色处理钻石的鉴定。样品颜色呈现不同饱和度的紫红色,净水称重法测试比重为3.52,放大观察,样品DR-2与DR-3的部分刻面光泽较弱,显示了未被重新抛光的严重烧蚀区域,石墨化沿内应力断裂明显,其表面可能经过高温高压处理。365nm长波紫外下,均呈现蓝色、橙红色、黄色和绿色混合的白垩状荧光外观,无磷光现象,而天然紫红色钻石为蓝色荧光或无荧光。宽频诱导发光图像仪GV5000深紫外下均呈现橙红色和蓝色混合荧光,无磷光现象。红外光谱中红外区均显示集合体氮相关的A中心和B中心,归类为IaAB型,且具有H1a辐照退火相关的特征峰,红外光谱近红外区均显示H1b,H1c辐照退火相关的特征峰与H2中心的特征峰。紫外可见近红外分光光度计均显示明显的NV-中心,H2中心和806 nm吸收峰,400~460和570 nm宽带处反射率的变化分别与N3中心和NV0中心相关,明显的NV-中心在天然紫红色钻石中极少发现,H2中心指示可能经过高温高压处理,可见光范围内对红光和蓝光的吸收较弱,所以呈现为紫红色外观。三维荧光光谱和光致发光光谱均显示出N3,H3,H4,NV0, NV-相关的发光中心,N3贡献蓝色荧光,H3和H4贡献黄绿色荧光,NV0与NV-贡献橙红色荧光。综合分析,三颗样品均为天然成因的钻石,后期经过高温高压,辐照,退火等多重处理,其紫红色主要由N3中心,NV0中心与NV-中心共同贡献。 相似文献
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Yaxian Zhu Lingyi Zhang Junhong Qian Fangyuan Gao Fei Ma Weibing Zhang 《Electrophoresis》2012,33(19-20):3028-3035
A continuous 2D ion exchange/RP CEC system was constructed in this report and retention characteristics of weak monoprotic acids in the column were investigated theoretically. The transport equations were deduced for predicting migration behavior of weak monoportic acids based on mixing model combining ion exchange, RP, and electrophoretic separation mechanism. The influences of separation voltage, length of capillary, pH value, and ionic strength of buffer and concentration of organic modifier in mobile phase on the separation were well described by the equations. It was verified that the migration rate of solute was linearly related to voltage in the case of lower voltage, decreased with the increase of the first‐dimensional length, and . The retention time of solute increased with enhancing ionic strength and concentration of organic modifier. These theoretical results were all demonstrated by the relevant experiments. The relevant application was performed for the aqueous extract of Rhizoma gastrodiae, showing the obvious potential in method development for the analysis of complex samples. 相似文献