Solid phase extraction of lanthanum on modified low-polar sorbents

The preconcentration of lanthanum has been studied on low-polar sorbents modified with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one, including hexadecylsilica, hyper-crosslinked polystyrene, polyvinylidene difluoride F2M, and activated carbon. The coefficients of reagent and the lanthanum distribution have been calculated under dynamic conditions. The leaching of the attached reagent from the sorbent surface has been investigated. The recovery of lanthanum with modified and nonmodified sorbents has been compared. The efficiency of lanthanum desorption with nitric acid and ethanol has been studied.     

Synthesis of new 1,2,4-triazolines and 1,3,4-thiadiazolines from bithioureas

2,4-Disubstituted thiosemicarbazides 1 react with acyl isothiocyanates to give bithioureas 2 , which by the action of sodium ethanolate cyclize to 1,2,4-triazoline-3-thiones 3 and 5 , respectively. Treatment of 2 with methyl iodide yields 1,3,4-thiadiazoline-2-imines 8 isomeric with 3 . Compound 8d undergoes a thermal induced DIMROTH rearrangement to give 3d in good yield.     

SYNTHESIS OF CATALYSIS BY THE FUNCTIONALIZATION OF SILICA AND ITS APPLICATIONS

Hybrid organic-inorganic silica materials containing organic functional groups have been preparedby the reaction of activated silica with a silane coupling reagent such as N-(2-aminoethyl)3-aminopropyltrimethoxysilane. The hybrid silica was further modified by organic compounds having abifunctional group. These modified hybrid silicas were used as catalysts for various nucleophilic reactions.And also, these were complexed with metallic ions for use as catalysts for oxygen oxidation of hydrocarbons.     

Studies towards the synthesis of epothilone A via organoboranes

Studies towards the synthesis of epothilone A via organoboranes have been described. A modified procedure for the large-scale preparation of B-gamma,gamma-dimethylallyldiisopinocampheylborane from prenyl alcohol has been developed. This reagent, upon reaction with various aldehydes, provides the corresponding alpha,alpha-dimethylhomoallylic alcohols in high enantioselectivities. The application of this reagent for the synthesis of the C1-C6 subunit of epothilone has been demonstrated. Alternatively, inter- and intramolecular asymmetric reduction protocols have also been utilized for the synthesis of the C1-C6 subunit of epothilone A. The synthesis of the C7-C21 fragment of epothilone A involving asymmetric alkoxyallyl- and crotylboration using alpha-pinene-derived reagents has also been described.     

C_8芳烃异构体+异丙醇或叔丁醇体系的恒压汽液平衡

这是为了较好地解决高效分离混合二甲苯所进行的一项基础性研究。准确测定了 0 .0 999MPa压力下邻、间、对二甲苯或乙苯 +异丙醇或叔丁醇八个体系的恒压汽液平衡数据 ,计算了该压力下八个体系中二组分的活度系数 ,作出了各体系的汽液平衡曲线及活度系数曲线 ,并讨论所呈现的规律。     

分光光度法测定有机磷的研究

本文对测定有机磷的一种方法作了研究。考察了温度、时间、磷试剂用量等影响因素。并用此法对淀粉含磷量进行测定。结果表明该法对淀粉有机磷的测定是准确的。     

Creation of hoop- and bowl-shaped benzenoid systems by selective detraction of [60]fullerene conjugation. [10]cyclophenacene and fused corannulene derivatives

Selective penta-addition of a methylcopper reagent followed by addition of a phenylcopper reagent to a suitably modified synthetic intermediate results in creation of 40pi-electron systems-hoop- and bowl-shaped cyclic benzenoid compounds, [10]cyclophenacene, and dibenzo-fused corannulene derivatives. The 40pi-electron cyclophenacene derivatives have been found to be chemically stable, yellow-colored, luminescent (560 nm), and EPR-silent. X-ray crystallographic analysis provided precision structural data sets. The dibenzo-fused corannulene derivatives exhibit blue-green (460 nm) to red (649 nm) fluorescence.     

Characterization of the heterogeneity of polyethylene glycol-modified superoxide dismutase by chromatographic and electrophoretic techniques.

Covalent attachment of polyethylene glycol (PEG) chains to the enzyme Cu,Zn-superoxide dismutase (SOD) produces a heterogeneous mixture of modified protein species. The heterogeneity of the product (PEG-SOD) derives from a variable stoichiometric combination of PEG with individual SOD molecules in addition to the polydispersity of the PEG reagent. Characterization of PEG-SOD presents significant challenges due in part to this heterogeneity in addition to the hybrid nature of the modified enzyme. The application of classical methods of protein characterization is not always successful for these PEG-proteins requiring the development of alternative or modified procedures. A series of chromatographic techniques including reversed-phase, ion-exchange, size-exclusion, and hydrophobic interaction high-performance liquid chromatography along with electrophoretic techniques including isoelectric focusing, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and capillary zone electrophoresis have been developed for assessing the degree of heterogeneity of PEG-SOD samples which encompass a range of different stoichiometries. Examples will be given demonstrating the application of these techniques to characterize PEG-SOD samples of different composition produced during the course of the reaction between SOD and an activated PEG reagent.     

Carbon,natural and synthetic sorbents for decontamination of objects of ecosystems from pathogenic microflora

Physico-chemical characteristics and sorption activity of carbon, organosilica sorbents and their modified forms towards proteins, possessing specific activity, and cholerae vibrio have been studied. It was found, that carbon materials modified by copper (II) effectively extracts cholerae vibrio (100%) and may be recommended for disinfection of drinking water. Sorption capacity of organosilica sorbents and their modified by copper (II) forms towards pathogenic microflora (E.coli, St.aureus, Ps.aeruginosa) depending on the composition of the sorbents, concentration of the modified reagent, pH of medium have been evaluated. The rows of the increase of sorption of pathogenic microorganisms by synthetic sorbents in water-salt solutions were established: Al(III)<Zn(II)<Cu (II). It was shown that inhibiting effect of modified synthetic organosilica and natural sorbents towards such pathogenic microorganisms as E-coli, St.aureus Ps.aeruginosa and fungus Bacillus pyocyaneus accordingly is equal 80–98%.     

Spectrophotometric evaluation of interferences in three iron reactions for the determination of serum total cholesterol

A spectrophotometric and chemical evaluation of reported interferences for three iron reactions for the determinations of serum cholesterol has been presented. It has been shown that all three reactions are affected by various interfering substances, such as 2-thiouracil, nitrate, azide, bromide, diethylstilbesterol, and steroids. Spectral differences between the reactions are probably due to solvent and anion effects.The incorporation of uranyl acetate as a precipitating agent into the ferric acetate-uranyl acetate procedure did not make the results obtained comparable with the Abell-type extract of a very icteric serum. Incorporation of ferrous sulfate does not noticeably affect the intensity or stability of color development with standards.As proposed, the ferric acetate-uranyl acetate procedure for the determination of cholesterol represents a modified iron reagent, but the reaction mechanism and the procedure described for it is neither new nor direct. The use of the ferric acetate reagent for serum cholesterol as opposed to ferric chloride, ferric ammonium chloride, or ferric perchlorate appears to have no real advantages as a color reaction. In fact the reaction is less sensitive while reagent preparation is more tedious, time consuming, and expensive than the ferric chloride procedure. Although no quantitative studies were performed, the only effects that chloride had on the reactions were in the region of 400 nm, a wavelength sufficiently far enough away from the 560-nm peak that it did not affect determinations. The concept that the ferric acetate-uranyl acetate reagent contains only acetate and sulfate anions is nullified as soon as one adds serum to the reagents.     

On the detection of aluminium by means of aluminon

The well-known reaction of aluminium with aluminon has been modified in such a way as to make it specific for this element. This has been accomplished by adding sulphurous acid beforehand and ethanol and hydrochloric acid afterwards. Thc first reagent prevents the interference of chromium, indium, gallium, and titranium; the second those of beryllium, scandium, zirconium and small amounts of ferric iron.     

New procedure of silica gel surface modification preparation of gaseous standard mixtures for calibration purposes

The new type of silica gel surface modification with using the trimethylamine as a reagent is described. The samples of chemically modified silica gel have been used for generation of gaseous standard mixtures (methyl chloride as a measurand) using the technique of thermal decomposition of the surface compound. The main aim of the research was to check the suitability of the new type of silica gel surface modification for obtaining methyl chloride as a measurand of gaseous standard mixture. The gaseous standard mixture obtained with using this technique was used for calibration of a thermal desorber-gas chromatography-flame ionization detector (TD-GC-FID) system. The homogeneity of coverage of silica gel surface with the immobilized compound has been evaluated. The full uncertainty budget of determination of liberated amount of methyl chloride has been calculated. The average amount of methyl chloride liberated from the unit sample of chemically modified silica gel is 3.59 +/- 0.13 mg g(-1). The influence of the modification way on the amount of liberated analyte has also been determined.     

A modified silver staining protocol for visualization of proteins compatible with matrix-assisted laser desorption/ionization and electrospray ionization-mass spectrometry

The growing availability of genomic sequence information, together with improvements in analytical methodology, have enabled high throughput, high sensitivity protein identification. Silver staining remains the most sensitive method for visualization of proteins separated by two-dimensional gel electrophoresis (2-D PAGE). Several silver staining protocols have been developed which offer improved compatibility with subsequent mass spectrometric analysis. We describe a modified silver staining method that is available as a commercial kit (Silver Stain PlusOne; Amersham Pharmacia Biotech, Amersham, UK). The 2-D patterns abtained with this modified protocol are comparable to those from other silver staining methods. Omitting the sensitizing reagent allows higher loading without saturation, which facilitates protein identification and quantitation. We show that tryptic digests of proteins visualized by the modified stain afford excellent mass spectra by both matrix-assisted laser desorption/ionization and tandem electrospray ionization. We conclude that the modified silver staining protocol is highly compatible with subsequent mass spectrometric analysis.     

Synthesis of trifluoroacetyl derivatives of oligopeptides forming analogs of the phosphorylatable section 33–40 of histone H1

A number of peptide fragments forming analogs of section 33–40 of histone H1, including the phosphorylatable serine-37 residue have been synthesized by the carbodiimide and modified azide methods. The specific introduction of trifluoroacetyl labels at the free α-amino groups of the peptides has been effected under conditions in which the other side chains were blocked by benzyloxycarbonyl (Z) protection. Thioethyl trifluoroacetate was used as the trifluoroacetylating reagent. The Z groups were removed from the final products by the action of HBr in absolute CF₃COOH.     

Retention behavior of aromatic hydrocarbons and dansylamino acids in reversed-phase liquid chromatography with cation-exchange-induced stationary phases

The retention behavior of aromatic hydrocarbons and dansylamino acids on cation-exchangers modified with alkylammonium ions has been examined by microcolumn liquid chromatography. Several parameters affected the retention of analytes, involving concentration of the modifier in the mobile phase, its alkyl chain length and mobile phase composition. Stationary phases modified with a reagent having longer alkyl chains achieved better column efficiency.     

Electrografting: a powerful method for surface modification

Electrografting refers to the electrochemical reaction that permits organic layers to be attached to solid conducting substrates. This definition can be extended to reactions involving an electron transfer between the substrate to be modified and the reagent, but also to examples where a reducing or oxidizing reagent is added to produce the reactive species. These methods are interesting as they provide a real bond between the surface and the organic layer. Electrografting applies to a variety of substrates including carbon, metals and their oxides, but also dielectrics such as polymers. Since the 1980s several methods have been developed, either by reduction or oxidation, and some of them have reached an industrial stage. This critical review describes the methods that are used for electrografting, their mechanism, the formation and growth of the layers as well as their applications (742 references).     

NMR kinetic studies on the decomposition of beta-amidozinc reagents: optimization of palladium-catalyzed cross-coupling with acid chlorides

The decomposition of beta-amidozinc reagent 4 by beta-elimination has been shown to be a unimolecular process in both THF and DMF as solvent, with relative rates of 4:1 at room temperature, and activation parameters have been determined. These results indicate the beta-elimination is a syn-process. NMR experiments reveal that as little as 2 equiv of DMF can have a significant stabilizing influence on reagent 4. Use of a mixture of DMA and toluene as the bulk solvent, in place of DMF, has allowed successful palladium-catalyzed cross-coupling reactions of both 4 and the homologous reagent 5 with acid chlorides to yield unsymmetrical ketones (nine examples).     

Modification of interlayer space of kanemite with trimethylsilyl groups: structure and adsorption properties

Interlayer hydroxyl groups of layered silicate kanemite have been modified with trimethylsilyl groups by the reaction between the hydroxyl groups and trimethylchlorosilane. Expansion of the interlayer space by intercalation of dimethyldialkylammonium ions into the silicate layers enables the silylating reagent to access the hydroxyl groups. An increase in specific surface areas was observed with increasing concentration of trimethylsilyl groups. This result suggests that the interlayer space of kanemite can be used as an effective molecular adsorption space by weakening the interaction between the interlayer hydrogen bonds of hydroxyl groups. The modification of kanemite with trimethylsilyl groups restricted the adsorption of water below a monolayer capacity and was favorable for benzene adsorption.     

Application of a modified simplex method to the multivariable optimization of a new FIA system for the determination of osmium

A methodology based on the coupling of experimental design and a modified simplex method is proposed for the optimization of a new flow injection-kinetic system for the spectrophotometric determination of Os (IV) with m-acetylchlorophosphonazo, which has for the first time been used as chromogenic reagent in the quantitative analysis of this element. An orthogonal array design is utilized to design the experimental protocol, in which six variables are varied simultaneously, and obtain the initial simplex using 25 experiments. A modified simplex method is applied to continuously optimize the data of the orthogonal array design; the search for optimum conditions of 6 variables using the modified simplex method required only 25 experiments. The efficiency and simplicity of the coupling of the experimental design and the modified simplex method are attractive for the development of new analytical methods. The method has been applied to the determination of Os (IV) in a refined ore as well as in a secondary alloy and provided satisfactory results.     

Application of a modified simplex method to the multivariable optimization of a new FIA system for the determination of osmium

A methodology based on the coupling of experimental design and a modified simplex method is proposed for the optimization of a new flow injection-kinetic system for the spectrophotometric determination of Os (IV) with m-acetylchlorophosphonazo, which has for the first time been used as chromogenic reagent in the quantitative analysis of this element. An orthogonal array design is utilized to design the experimental protocol, in which six variables are varied simultaneously, and obtain the initial simplex using 25 experiments. A modified simplex method is applied to continuously optimize the data of the orthogonal array design; the search for optimum conditions of ¶6 variables using the modified simplex method required only 25 experiments. The efficiency and simplicity of the coupling of the experimental design and the modified simplex method are attractive for the development of new analytical methods. The method has been applied to the determination of Os (IV) in a refined ore as well as in a secondary alloy and provided satisfactory results.