A NEW METHOD FOR ESTIMATION OF WEIGHT-AVERAGE MOLECULAR WEIGHT OF POLYMER FROM THE INTRINSIC VISCOSITY AND CHROMATOGRAM

A new method is proposed for estimation of weight-average molecular weight from the intrinsicviscosity and GPC chromatogram of a polymer sample for which Mark-Houwink coefficients are notknown. The method bases on an approximate relationship between GPC data and the intrinsicviscosity of the sample. Reliability of this method was tested by comparing with the universalcalibration method which requires known Mark-Houwink coefficients for seven samples havingdifferent molecular weight distributions. Results obtained by the new method are in excellent agree-ment with those by the universal calibration method.     

A convenient one-step preparation of diaminonitrile compounds

A new method for preparation of diaminonitrile compounds is reported.In this method primary aliphatic diamine compounds were condensed with two equivalents of benzaldehyde and sodium cyanide in presence of an aqueous solution of sodium hydrogensulfite under mild conditions.This method provides an efficient,convenient and practical method for the syntheses of diaminonitrile compounds and the products are easily isolated.The prepared new compounds were characterized by elemental analysis,IR,NMR spectroscop...     

Determination of Size Distribution of Nano-particles by Capillary Zone Electrophoresis

A new method was developed for the determination of the size distribution of nano-particles by capillary zone electrophoresis (CZE). Scattering effect of nanoparticles was studied. This method for the determination of size distribution was statistical.     

Optimization of the separation of a mixture of unknown composition by reversed-phase HPLC

A method is presented for the computer-assisted optimization of mobile phaseselection for the separation of a synthetic intermediate of unknown composition by reversed-phase HPLC.The method is based on recognition of the order of the peaks by comparisonof peak area ratio and followed by the BSOS-L(Binary Solvent Optimization System forHPLC)method.Excellent agreement was obtained between predicted data and experimentalresults.     

Studies on Thermokinetics——Thermokinetic Method for Second Order Reactions

On the theoretical basis of thermokinetics,the dimensionless parameter method for second-order reactions is suggested in this paper.Through thermokinetic studies of two reaction systems,the fundamental equations of thermokinetic method for second-order reactions were verified.     

Syntheses of Iso-Condensed Heteroaromatic Pyrroles and the Application to the Total Synthese of Natural Products

A novel method, namely the intramolecular 1,3-dipolar cycloaddition and cycloreversion ofazido-alkylidene malonates, for the preparation of iso-condensed heteroaromatic pyrroles has beendeveloped. The application of this method for the synthesis of 2,4-dihydropyrrolo[3,4-b]indole ringsystem, as well as the application of this ring system for the total syntheses of ellipticine alkaloids arereported.     

Seed-mediated growth method for high-quality noble metal nanocrystals

This review highlights work from the authors’ laboratory on the recent development of seed-mediated growth method for noble metal nanocrystals. The seed-mediated growth method has become one of the most efficient and versatile methods for synthe-sizing high-quality noble metal nanocrystals. The seed-mediated growth method can separate the nucleation and growth stages of metal nanocrystals, and thus provide better control over the size, size distribution, and crystallographic evolution of metal nanocrystals. Because of its high controllability, the seed-mediated growth method is especially promising in providing mechanistic insights into the growth mechanisms of noble metal nanocrystals. In this review, the thermodynamic and kinetic parameters for the nucleation and growth of noble metal nanocrystals are systematically summarized. Mechanistic understanding of these parameters is provided. These studies provide useful guidelines for the rational design and synthesis of novel noble metal nanocrystals with high quality.     

SIMULTANEOUS DETERMINATION OF MULTICOMPONENT IN MIXED ACIDS BY MATHEMATICAL METHOD

A new method for the determination of components in mixed acids has beendeveloped.The mathematical model is obtained from samples of known composition and isthen used to predict the concentrations of components in unknown sample.The practicalutility of this method is demonstrated for simultaneous determination of two systems ofternary mixed acids and the results are satisfactory.     

Determination of Specific Refractive Index Increment （dn/dc）_μ at a Constant Chemical Potential,for Solutions of Polymer in Mixed Solvents by the GPC Method

A new chromatographic method is described for the determination of specific refractive index increment(dn/dc)μ at a constant chemical potential,for polymer/mixed solvent systems.In this method the(dn/dc)is obtained by measuring the areas of solvated-polymer peaks when the mixed solvent is used as an eluent.Values of(dn/dc)μ for the poly(dimethylsiloxane)(PDMS)-benzene-methanol system,determined by the proposed method are in good agreement with those determined by the conventional dialysis method.The new approach has the advantages of simplicity,fast speed,and high reproducibility.The experimental results for stearic acid-chloroform-methanol system show that this method can also be applied to nonpolymer/mixed solvent systems for the determination of(dn/dc)μ.     

流动相离子色谱法测定化肥催化剂中硫酸根

This paper describes a method for determination of sulfate in fertilizer catalyst by the use of an active aluminium oxide column for separation and mobile phase ion chromatography. The recoveries of this method were from 99.7% to 102.2%. The coefficient of variation ranged from 2.13% to 5.50%. The results are satisfactory. The method is reliable,simple, accurate and applicable to the determination of sulfate in fertilizer catalyst after a pretreatment by hydrochloric acid.     

Birefringence of highly oriented fibers

A spectrophotometric method was developed for measuring the birefringence of highly oriented synthetic fibers. This method surmounts the low birefringence limit of the standard quartz compensator method and the difficulties in interpretation of the photographic fringe method. A highly oriented aramid fiber gave birefringence values of 0.60–0.75 by this method, compared with 0.25 for polyester and 0.06 for nylon by other conventional methods. The operating principles and excellent results of this new method provide a basis for the extension of routine birefringence characterization to highly oriented fibers.     

Modeling of Mechanical Properties of Polymeric Systems with Branching/Crosslinking,Particularly Their Mechanical Resistence and Stability

A theoretical method for the estimation of mechanical characteristics of polymeric structures is proposed. This method uses the statistical polymer method for modeling branched/crosslinked structures. The proposed method is utilized for the estimation of mechanical resistance and stability of microporous polymeric materials. An engineering method for the evaluation of mechanical stability and resistance of polymeric materials is derived.     

The use of polyanions of hydrazines in the synthesis of heterocycles

A novel method for the synthesis of cyclic hydrazine derivatives is reported. The new method for the generation of nitrogen-containing heterocycles is based on a polyanion strategy. The described method provides a convenient access to cyclic hydrazine derivatives, which are extensively used in drug industry and agriculture. The advantages and limitations of the new method are also demonstrated.     

Kinetic analysis of nonisothermal solid-state reactions: determination of the kinetic parameters by means of a nonlinear regression method

A nonlinear regression method has been proposed for a simultaneous calculation of the activation energy, frequency factor, and reaction order from a single TG curve. This method was based on the new temperature integral approximation proposed in this paper and the Levenberg–Marquardt method. The newly proposed nonlinear regression method was applied for determining the kinetic parameters from two simulated TG curves. The results of the calculations were compared with values obtained by the traditional method. It can be concluded from this comparison that the new nonlinear regression method is more accurate than the traditional method for the determination of the kinetic parameters of solid-state heterogeneous reactions.     

A characterization of pairs of subspaces for quantum chemical applications of the Galerkin–Petrov method

A method is proposed for characterizing pairs of finite dimensional subspaces of the Hilbert space. The method might be helpful for the proper selection of coordinate and projective spaces leading to reliable realizations of the Galerkin–Petrov method for use in quantum chemistry. In order to illustrate the method some numerical results are presented.     

Evaluation of a dry, rehydratable film method for rapid enumeration of Staphylococcus aureus

Results with the new 3M Petrifilm Rapid S. aureus Count (RSA) Plate method were compared with those of the classical Baird-Parker agar (BPA) method for detection and enumeration of Staphylococcus aureus. Studies on 219 bacterial strains demonstrated that the Petrifilm RSA plate is more sensitive than and as specific as the classical BPA method for confirmed identification of S. aureus. Counts of colonies from 71 pure cultures, 61 naturally contaminated food samples, and more than 750 artificially inoculated food samples showed that the Petrifilm RSA method was as effective as the classical BPA method for identification and enumeration of S. aureus. The Petrifilm RSA method gave results in one-third the time required for the classical method.     

Disintegration test to measure lot-to-lot variations of vaginal tablets

Attempts were made to investigate the disintegration test for vaginal tablets. Disintegration tests were done for four different commercial vaginal tablets (three lots each) by the watch glass method and Japanese Pharmacopoeia (JP) disintegration method, and the resulting profiles were compared to those by the modified British Pharmacopoeia (BP) method on a point of lot-to-lot variation of the disintegration times. The disintegration time of every tablet by the modified BP method was longest, followed by the watch glass method, and finally by the JP disintegration method. The results for lot-to-lot differences in disintegration times by the modified BP method were similar to those by the watch glass method. However, such lot-to-lot differences as found by the modified BP method and watch glass method were not always observed by the JP disintegration method. It was concluded from these results that the modified BP method was most suitable for investigating lot-to-lot differences in the disintegration of vaginal tablets.     

pH计检定仪期间核查方法

介绍pH计检定仪的4种期间核查方法:传递比较法、多台对比法、留样测量法、实验室间比对法。传递比较法能直接反应pH计检定仪的变化,适用于已建立pH计检定仪检定装置的单位;多台对比法与留样测量法方便、快捷,可操作性强,适合大多数单位进行pH计检定仪的期间核查;实验室间比对法对设备要求较低,但需要协调的单位较多,周期较长,费用较高,实用性差。     

Evaluation of some methods of determination of starch for legislative purposes in the European Community.

A newly developed enzymic method for starch purity determination has been designed in response to the search by the European Community (EC) for a reliable and accurate official method for direct total starch measurement of high purity starches. This new method, the Birmingham method, utilizes a multi-enzyme regime, consisting of an (-amylase (E.C. 3.2.1.1), a glucoamylase (E.C. 3.2.1.2) and a pullulanase (E.C. 3.2.1.41), for the complete and specific hydrolysis of starch to glucose. Greater than 99.5 % conversion of most starches to glucose is achieved which is higher than that afforded by other enzymic methods being considered for adoption. In this communication the reliability and accuracy of this method are assessed and demonstrated. Also, some results during its development are presented. Advantages and drawbacks of the other methods for starch purity measurement being investigated/assessed for permanent adoption as an official method of the EC are also discussed.