摘要:

The concentration profiles and the concentration dependent diffusion coefficient, at steady-state liquid permeation, were investigated in plastic films by directly measuring the concentration profile. A stacked film packet was developed which permitted peeling of film sections and measuring incremental concentration of permeate. The membrane-permeate systems studied were: nylon 6-water, nylon 6-dioxane, cellulose acetate-water, and polyethylene-dioxane. Membrane thickness was varied from 2 to 53 mil and temperature from 35 to 75°C. Also, poylethylene-benzene and polyethylene–n.-hexane systems were studied at 17 mil and 35°C only.

ISSN:0037-2366    

DOI:10.1080/00372367008055530

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The validity of several local plate height equations is studied using programmed pressure gas chromatography. The appropriate numerical methods of calculation as well as the experimental results obtained are given. Comparison between calculated data and the experimental results shows that the theory cannot meet the programmed flow-rate requirements in its present state. The discrepancy between the calculations and the experiments comes from the fundamental basis of the theory.

ISSN:0037-2366    

DOI:10.1080/00372367008055531

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The cation exchange behavior of bismuth was studied on Dowex 50W-X8 with hydrochloric, sulfuric, nitric, and perchloric acids, with ammonium chloride and sodium nitrate as the eluting agents. The efficiency of eluants was evolved in terms of elution constant and volume distribution coefficient. Bismuth was separated from copper, cadmium, tin, aluminum, nickel, manganese, vanadium, magnesium, mercury, iron, zinc, silver, cobalty barium, and calcium by the gradient elution process. It was separated from lead, uranium, antimony, and strontium by selective elution with specific eluants. The oxyanions were separated from it by the selective sorption process. The method was found to be applicable to analysis of bismuth-based alloys.

ISSN:0037-2366    

DOI:10.1080/00372367008055532

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

We have developed an inexpensive device which, when used with a Technicon proportioning pump, will prepare reproducible density gradients of viscous solutions.

ISSN:0037-2366    

DOI:10.1080/00372367008055533

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Means are proposed for controlling retention and thus for instituting retention programming in exclusion chromatography. Control is to be gained by the addition of a high molecular weight polymer to the incoming solvent. Preliminary data confirm that such a polymer strongly affects retention.

ISSN:0037-2366    

DOI:10.1080/00372367008055534

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Overload phenomena in GPC are investigated with samples of narrow polystyrenes and short but efficient columns packed with Styragel. Viscous fingering is shown to be a leading cause of peak skewing and broadening. A correlation is proposed to define a safe operating range in terms of sample concentration, volume, and the average intrinsic viscosity of the solute polymer.

ISSN:0037-2366    

DOI:10.1080/00372367008055535

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Gel permeation chromatograms are usually subjected to mathematical analyses of varying degrees of complexity to obtain molecular weight distribution and analytical data. Hand reduction of the recorder output data is difficult and time consuming even on an occasional basis. This paper describes in detail the modifications necessary to adapt the Waters Gel Permeation Chromatograph Model 200 for on-line data acquisition by a computer equipped with an analog to digital converter (IBM 1800). Since the operation is done in the background mode, time sharing with several other users or instruments is possible. Modifications to the auto injection unit are also described. This system has proven to remove all of the usual hand data reduction steps and to be extremely flexible for nonroutine analyses.

ISSN:0037-2366    

DOI:10.1080/00372367008055536

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

High resolution in gel permeation chromatography has been accomplished by use of long columns, since commercial rigid gels afford relatively fixed capacity ratios and since plate numbers of equivalent columns are additive. To overcome the high cost and high pressure requirement of long columns often required to resolve discrete species, high resolution gel permeation chromatography may be attained in commercial GPC equipment by recycle operation through the reciprocating pump, GPC column, and detector. However, peak width increases with the number of cycles (μ). Since the contained volume of the closed recycle system is constant, asvincreases the peak width (W) of the distribution will eventually exceed the volume of the system and peak overlap will occur. This presentation considers the increase inWand provides a method of “flush and draw off” to prevent sample overlap. Analytical and preparative scale separations were investigated, using both small and macromolecules. The effects of sample load and flow rate on-resolution with recycle operation were investigated.

ISSN:0037-2366    

DOI:10.1080/00372367008055537

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A systematic study of the major factors influencing fast analysis by gel permeation chromatography is presented. The study included the effects of (a) solvent flow rate [1–35 ml/min], (b) sample concentration [0.05–0.5%], (c) sample molecular weight [41–411,000 mol wt] and (d) particle size of column packing [10–42μ]. The effect of the operating temperature at the high flow rates was also investigated.

ISSN:0037-2366    

DOI:10.1080/00372367008055538

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

High loads on GPC columns usually lead to poor efficiency because of steep viscosity gradients. A great difference in density between solution and solvent can also cause excessive band broadening. However, under certain conditions good separations are achieved with loads of 150 mg/100 cc column volume and higher. Two mechanisms are proposed to explain this phenomenon. Secondary exclusion is caused by obstruction of pores to larger molecules by the more rapidly diffusing small molecules. It takes place predominantly with molecules of less than 2000 molecular weight in small pore gels. Incompatibility is caused by repulsive interaction between solute molecules and the polystyrene gel. It is observed with solutes which are chemically quite different from polystyrene, e.g., with polyvinyl acetate, and in a low to intermediate molecular weight range.

ISSN:0037-2366    

DOI:10.1080/00372367008055539

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor