摘要:

The approximations necessary to compare theory and performance in large-scale chromatographic columns are critically analyzed. The existence of carrier gas velocity gradients across the column cross section is the major cause of band-broadening and inefficiency in large-scale columns. Estimates of these radial velocity gradients based on existing particle size and velocity measurements are shown to be too inexact to test the presently accepted theory. A radial velocity profile, which has the major features of profiles measured in somewhat similar systems, is proposed. The need for accurate measurements of velocity profiles is emphasized.

ISSN:0037-2366    

DOI:10.1080/00372367108058951

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The frontal (multiple-input) approach is applied to countercurrent distribution. Equations are derived for calculating the number of tubes required for a given separation or for calculating the amount of solute emerging at the intersection of two solute profiles. In both cases ideal behavior is assumed. The applicability of these equations to preparative fractionations is evaluated and the utility of the frontal technique demonstrated.

ISSN:0037-2366    

DOI:10.1080/00372367108058952

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The permeability constants of oxygen and carbon dioxide through hydrated potassium acrylate-grafted polyethylene films increase rapidly as the degree of hydration of the films increases above about 28 wt %. Below about 28 wt %, the carbon dioxide permeability constant increases with the degree of hydration. In the case of oxygen, the opposite is true.

ISSN:0037-2366    

DOI:10.1080/00372367108058953

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Mixed solvents containing an organic extractant provide selective separations of metal ions on cation- and anion-exchange papers. The separations of scandium, hafnium plus zirconium, nickel, and thorium from complex mixtures are demonstrated. Various separations in dithizone and dimethyl-sulfoxide media are also reported. Results are often the same as those achieved on columns of resin with the same mobile phase.

ISSN:0037-2366    

DOI:10.1080/00372367108058954

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Gel permeation chromatograms are interpreted in terms ofV, the peak elution volume, which is characteristic for the size of the solute species. If solute association takes place,Vmay become extensively concentration dependent. To further the understanding of this effect a simple theory, which ignores axial diffusion, has been developed, the model for molecular association being a micellar surfactant in equilibrium with its monomer.

ISSN:0037-2366    

DOI:10.1080/00372367108058955

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

An equilibrium method for determining macromolecular association by gel permeation is described. A thermodynamic description of the simplest case, dimerization, is presented in terms of the equilibrium constant for association, and equilibrium partition coefficients for species present. The theoretical analysis yields an equation relating the equivalents of monomer in the external phase to total equivalents, from which the equilibrium constant for association may be obtained.

ISSN:0037-2366    

DOI:10.1080/00372367108058956

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The technique of gel filtration chromatography is described, with a guide to relevant literature on methods, theory, and applications, especially the use of GFC in analysis of molecular interactions, both macromolecular and small molecule-macromolecule aggregation.

ISSN:0037-2366    

DOI:10.1080/00372367108058957

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Most of the common GPC gels exhibit pore sizes which are too small to separate very extended molecules, e.g., native cellulose in solution. Several gel types were tested with vinyl polymers of molecular weights up to 107and with cellulose nitrate. Large pore size Styragel with acetone as solvent proved to be the most favorable gel system yielding effective separations for polymers with coil diameters in solution up to 4000 Å.

ISSN:0037-2366    

DOI:10.1080/00372367108058958

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

The calibration of gel permeation chromatograph (GPC) for a given polymer type is usually done by running well-characterized polymer samples of the same type. The available polystyrene and polyglycol standards with molecular weights below 5000 do not give parallel calibration curves, and the points for polystyrene are not on an extension of the higher-molecular-weight portion of the curve. In order to check the calibration in this low molecular-weight region and to establish an independent curve for polybutadiene, a polybutadiene sample prepared by a-methylstyrene tetramer-Na2initiation was chromatographed. In doing this, dual detection was used, consisting of a differential refractometer, and an ultraviolet absorption spectrophotometer.

ISSN:0037-2366    

DOI:10.1080/00372367108058959

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

An ultraviolet detector was added to the GPC making it possible to determine both molecular weight distribution and composition of butadiene-styrene copolymers as a function of molecular weight. After calibration, several types of commercial and experimental copolymers were analyzed. SBR was found to have a very uniform composition over most of the range of molecular weight. However, the styrene content decreased at the high end of the distribution. Representative samples of anionically polymerized copolymers were also examined. In general, the composition of these polymers varied more than SBR. Usually, the styrene content was high at low molecular weight and decreased as molecular weight increased. Several experimental copolymers that were first metalated and then grafted with styrene were studied. Incomplete grafting as well as the presence of low molecular weight homopolystyrene was readily detected. This appears to be a particularly sensitive method for studying composition of copolymers.

ISSN:0037-2366    

DOI:10.1080/00372367108058960

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor