Use of pervaporation for separating azeotropic mixtures using two different hollow fiber membranes

The performance of a “two-membrane column” was demonstrated for the separation of water-ethanol and water-isopropanol azeotropic mixtures. The cellulose acetate and silicone rubber membranes which were employed for the strippers showed opposite permselectivity towards each component of the mixtures. The two strippers were connected together with liquid pumps installed between them. A great increase in overall separation factor (over 100) was obtained. The degree of separation was dependent upon the ratio of feed to reject rate. Azeotropic mixtures were successfully separated by using the two-membrane column. This column is expected to provide us with an energy-saving, high purity separation process     

Use of high-speed liquid chromatography for separating the gibberellins and compounds related to them

Known methods of obtaining 4-bromophenacyl esters of the gibberellins are considered. A convenient method of obtaining 4-bromophenacyl esters of gibberellins, which are readily recorded by the UV detector of a liquid chromatograph, is described. The chromatographic separation has been performed of two model mixtures of esters of different polarities on fine-grained silica gel.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 228–231, March–April, 1980.     

Use of sephadex in the analysis of some flavonoids

Chemistry of Natural Compounds - The conditions of gel filtration, through Sephadex of 14 different flavonoids have been studied. It has been shown that the structure of the flavonoid compound...     

Use of sephadex in the analysis of some flavonoids

Conclusions The conditions of gel filtration, through Sephadex of 14 different flavonoids have been studied. It has been shown that the structure of the flavonoid compound affects the filtration process.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 4, pp. 415–417, 1970     

Use of zirconium(IV) and antimony(III) for structural investigation of flavonoids

Summary The absorption spectra (in the visible and ultraviolet) of the complexes formed in absolute methanol between Zr⁴⁺, V⁴⁺, Y³⁺ and Sb³⁺ with 3-hydroxyflavone, apigenin, hesperidin, naringenin, morin, kaempferol, quercetin, rutin and myricetin have been studied. Zr⁴⁺ and Sb³⁺ form complexes that are stable in acid medium. The stoichiometry of the vairous Zr⁴⁺-flavonoid complexes formed in methanol and methanol/HClO₄ media has been determined by the molar ratio method. The preferred sites for complex formation of flavonoids with Zr⁴⁺ are postulated. Zr⁴⁺ forms chelates with the 3-hydroxy-4-keto and 5-hydroxy-4-keto systems simultaneously. Sb³⁺ forms complexes only with the 3,5-dihydroxy system in flavonoids. The results permit estimation of the relative order of chelating power of each type of binding site and are useful in elucidation of the structure of the flavonoids.

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Verwendung von Zirkonium(III) und Antimon(III) für die Erforschung der Flavonoide

Zusammenfassung Die Absorptions-Spektren (im sichtbaren und UV-Bereich) der in absolutem Methanol hergestellten Komplexe von Zr⁴⁺, V⁴⁺, Y³⁺ und Sb³⁺ mit 3-Hydroxyflavon, Apigenin, Hesperidin, Naringenin, Morin, Kaempferol, Quercetin, Rutin und Myricetin wurden untersucht. Zr⁴⁺ und Sb³⁺ bilden in saurem Milieu beständige Komplexe. Die Stöchiometrie der verschiedenen Zr⁴⁺-Flavonoid-Komplexe, die in Methanol bzw. Methanol/ HClO₄ hergestellt wurden, wurde durch Bestimmung der Molarverhältnisse ermittelt. Die für die Komplexbildung bevorzugten Stellen (im Molekül) wurden angegeben. Zr⁴⁺ bildet Chelate mit der 3-Hydroxy-4-keto- und mit der 5-Hydroxy~4-ketogruppe. Sb³⁺ bildet solche Komplexe nur mit der 3,5-Dihydroxy-4-keto-Gruppe in Flavonoiden. Die Untersuchungsergebnisse ermöglichen die Abschätzung der Komplexbildungsfähigkeit der verschiedenen Gruppierungen und sind für die Strukturaufklärung von Nutzen.

     

Use of on-line liquid chromatography-nuclear magnetic resonance spectroscopy for the rapid investigation of flavonoids from Sorocea bomplandii

A HPLC method, using photochemically-induced fluorescence detection, is described for the separation and determination of four phenylurea herbicides including diuron, isoproturon, linuron and neburon. A post-column photoreactor, consisting of a reactor knitted around a 4 W xenon lamp, has been included between the column and the detector, in order to transform the non-fluorescent herbicides into fluorophors. The influence of mobile phase composition, flow-rate, pH, and buffer concentration has been studied. An acetonitrile–buffer solution of potassium phosphate dibasic of pH 7 and 0.01 M concentration (60:40, v/v), was selected as optimum. For the fluorimetric detection, optimal excitation/emission wavelengths 324/403, 301/433, 335/411 and 326/385 nm were selected for the determination of diuron, isoproturon, linuron and neburon, respectively. The detection limits ranged between 0.07 and 0.46 μg/ml, according to the compound.     

Use of diluted anion-exchange and hydrophobic properties in separating synthetic single-stranded oligodeoxyribonucleotides on mixed-ligand stationary phases

Summary Mixed-ligand or “mixed-interaction” stationary phases are composed of bonded silanes possessing both ionic and hydrophobic character. The complex retention properties exhibited by these phases have been particularly useful in separating large biomolecules, such as synthetic single-stranded oligodeoxyribonucleotides. By isolating the individual properties of separate ligands present in mixed-ligand stationary phases a better understanding of the heterogeneous surface was sought. Specifically a dilute anion-exchange mixed-ligand phase of 5% surface coverage showed dramatically different selectivity for oligomers compared to hydrophobic stationary phases. Of particular interest was the increased selectivity observed in separating oligonucleotides differing on the 3′ end over conventional reversed-phases supports.     

生物功能化中空纳米二氧化硅微球的构建及其对蛋白质的分离纯化

本文作者通过水热法合成了中空SiO_2-SH纳米微球,然后直接用其吸附Ni~(2+),从而形成SiO_2-SH-Ni~(2+)复合材料,以此材料为载体,可以将以组氨酸为标签的(His-tagged)的融合蛋白直接从细胞裂解液中进行分离纯化,实验结果表明,该微球适合于His-tagged融合蛋白的分离纯化.     

Analytical methods for separating and isolating magnetic nanoparticles

Despite the large body of literature describing the synthesis of magnetic nanoparticles, few analytical tools are commonly used for their purification and analysis. Due to their unique physical and chemical properties, magnetic nanoparticles are appealing candidates for biomedical applications and analytical separations. Yet in the absence of methods for assessing and assuring their purity, the ultimate use of magnetic particles and heterostructures is likely to be limited. In this review, we summarize the separation techniques that have been initially used for this purpose. For magnetic nanoparticles, it is the use of an applied magnetic flux or field gradient that enables separations. Flow based techniques are combined with applied magnetic fields to give methods such as magnetic field flow fractionation and high gradient magnetic separation. Additional techniques have been explored for manipulating particles in microfluidic channels and in mesoporous membranes. Further development of these and new analytical tools for separation and analysis of colloidal particles is critically important to enable the practical use of these, particularly for medicinal purposes.     

Porphyrin hetero-dimer as charge separating system for photocurrent generation

Introducing a porphyrin bearing electron acceptor onto a self-assembled monolayer (SAM) using a supramolecular method to form a hetero-dimer increased the photocurrent value compared with using porphyrin without an electron acceptor.     

Bipolar reverse osmosis membrane for separating mono-and divalent ions

Bipolar reverse osmosis membranes that have both negatively and positively charged layers have been prepared to enhance the selectivity towards mono- and divalent ions in respect of both cations and anions. Positively charged layers are formed on low pressure reverse osmosis membranes having negative charge (NTR-7410 and 7450) by an adsorption method using polyethyleneimine (PEI) or a quaternary ammonium polyelectrolyte (QAP). These layers attach to the membrane's dense layer, which is made of sulfonated polyether sulfone. The selectivity of mono- and divalent ions is proven by experimental results for single electrolytes (NaCl, Na₂SO₄ and MgCl₂). Although negatively charged membranes repulse divalent anions more strongly than cations and monovalent anions, bipolar reverse osmosis membranes reject both divalent cations and divalent anions better than monovalent ions. An optimal preparation method for bipolar membranes showing selectivity towards mono- and divalent ions were developed. The bipolar membranes showed good ion selectivity for artificial sea water.     

Liquid chromatography on unmodified and modified spheron gels I. Nucleosides,bases and related compounds

Summary The ethylene glycol methacrylate gel Spheron and ion exchangers produced by the chemical modification of this gel (such as the cation exchanger Spheron S and anion exchanger Spheron DEAE) are compared with octadecylsilica as column packing materials for reversedphase chromatography of nucleic acid constituents and related compounds. The different separation selectivities of the individual materials can be utilized for the chromatographic separation of these compounds.     

Use of expanded bed adsorption to purify flavonoids from Ginkgo biloba L.

Three techniques (liquid–liquid extraction, packed bed adsorption and expanded bed adsorption) have been compared for the purification of flavonoids from the leaves of Ginkgo biloba L. A crude Ginkgo extract was obtained by refluxing with ethanol for 3 h. The yield of flavonoids achieved by this crude extraction was about 19% (w/w) and the purity of flavonoids in the concentrated extract was between 1.9 and 2.3% (w/w). The crude extract was then dissolved in deionized water and centrifuged where necessary to prepare clarified feedstock for further purification. For the method using liquid–liquid extraction with ethyl acetate, the purity, concentration ratio and yield of flavonoids were 25.4–31.0%, 16–18 and >98%, respectively. For the method using packed bed adsorption, Amberlite XAD7HP was selected as the adsorbent and clarified extract was used as the feedstock. The dynamic adsorption breakthrough curves and elution profiles were measured. For a feedstock containing flavonoids at a concentration of 0.25 mg/mL, the appropriate loading volume to reach a 5% breakthrough point during the adsorption stage was estimated to be 550–600 mL for a packed bed of volume 53 mL and a flow rate of 183 cm/h. The results from the elution stage indicated that the majority of impurities were eluted by ethanol concentrations of 40% (v/v) or below and efficient separation of flavonoids from the impurities could be achieved by elution of the flavonoids with 50–80% ethanol reaching an average purity of ∼25%. The recovery yield of flavonoids using the packed bed purification method was about 60% of the flavonoids present in the clarified feedstock (corresponding to around 30% for the total flavonoids in the unclarified crude extract). For the method using expanded bed adsorption also conducted with Amberlite XAD7HP as the adsorbent, the optimal operation conditions scouted during the packed bed experiments were used but unclarified crude extract could be loaded directly into the column. For an expanded bed with a settled bed height of 30 cm, the loss of flavonoids in the column flow-through was about 30%. The two-step elution protocol again proved to be effective in separating the adsorbed impurities and flavonoids. More than 96% of the bound impurities were completely removed by 40% ethanol in the first elution stage and less than 4% remained in the final product eluted by 90% ethanol in the second elution stage. Also, ∼74% of the adsorbed flavonoids on column (corresponding to 51% of the total flavonoids in the unclarified feedstock) were recovered in the product. In addition to higher recovery yield, the average process time to obtain the same amount of product was decreased in the expanded bed adsorption (EBA) process. The results suggest that the adoption of EBA procedures can greatly simplify the process flow sheet and in addition reduce the cost and time to purify flavonoids from Ginkgo biloba. These results clearly demonstrate the potential for the use of EBA to purify pharmaceuticals from plant sources.     

生产银杏黄酮的模拟移动床色谱工艺

世界各国银杏黄酮类药品的标度为总黄酮含量24％,生产工艺主要是浸取。现在国内有厂家提出制备高纯度银杏黄酮产品——总黄酮含量44％,生产工艺主要包括浸取和提纯两步,提纯主要采用树脂柱层析法。本文用模拟移动床色谱(Sinulated Moving Bed Chromatography,简称SMBC)提纯生产工艺,所得黄酮纯度可达90％以上。     

Design of a production gas chromatograph for separating heat-sensitive materials

Summary A rational design procedure for production and preparative chromatography has previously been devised. Here the procedure is applied to designing a pilot scale production gas chromatograph for separating two heatsensitive essential oil mixtures: geraniol/nerol and -/-pinenes. Analytical scale experiments provide some of the data required. A critical feature of the design is that these materials degrade at temperatures well below their boiling points. The design study leads, first, to selection of carrier gas, stationary phase and solid support materials, and then to quantitative determination of column temperature, evaporator temperature, feed concentration in the carrier gas, column diameter, particle size of support, carrier velocity, ratio of recycled to inject feed, injection time, column length, and liquid phase loading.Presented at the 14th International Symposium on Chromatography London, September, 1982.     

Chemistry of modified flavonoids 17. Imidazole analogs of flavonoids

Summary Imidazole analogs of chalcones were synthesized by the reaction of 1-methyl-2 formyl-5-chloroimidazole with o-hydroxyacetophenones. Isomerization and oxidative cyclization of chalcones yielded imidazole analogs of flavonones and flavones. These compounds were used in the synthesis of pyrazolines, pyrazoles, and isoxazoles.Taras Shevchenko Kiev University, Kiev 252017. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1063-1070, August, 1994.For Communication 16 see [1].     

Analytical separation and detection methods for flavonoids

Flavonoids receive considerable attention in the literature, specifically because of their biological and physiological importance. This review focuses on separation and detection methods for flavonoids and their application to plants, food, drinks and biological fluids. The topics that will be discussed are sample treatment, column liquid chromatography (LC), but also methods such as gas chromatography (GC), capillary electrophoresis (CE) and thin-layer chromatography (TLC), various detection methods and structural characterization. Because of the increasing interest in structure elucidation of flavonoids, special attention will be devoted to the use of tandem-mass spectrometric (MS/MS) techniques for the characterization of several important sub-classes, and to the potential of combined diode-array UV (DAD UV), tandem-MS and nuclear magnetic resonance (NMR) detection for unambiguous identification. Emphasis will be on recent developments and trends.