摘要:

AbstractThe early history of the author's contributions to the origin and development of gel permeation chromatography is recounted. Previous experiences with chromatography and with polymer characterization were of value at the inception. Early problems involved the control of gel structure and particle size, column‐packing techniques, design, and test methods for the instrumentation. Aid from co‐workers is acknowled

ISSN:0449-2994    

DOI:10.1002/polc.5070210103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractAn equation describing the relationship between the GPC determined breadth of the molecular weight distribution, (σn/Mn)G, the true breadth of the distribution,σn/Mn, zone spreading or tailing ΔVe, and the separability employed,K(M), has been derived:.HereK(M) is the absolute value of the derivativedVe/dM, in whichVeis elution volume andMis molecular weight. The validity of this equation was established through GPC fractionations of blends of narrow molecular weight distribution polystyrenes. Application of the equation to experimental data shows that ΔVeincreases with increasingM. The equation indicates that GPC molecular weight data are less in error with polymers of broader molecular weight distributions and with larger values ofK(M). The importance of the experimental variableK(M) is that it defines the degree of fractionation, higher values ofK(M) denoting more complete fractionat

ISSN:0449-2994    

DOI:10.1002/polc.5070210104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractFormulas are developed for describing resolution in gel permeation chromatography (GPC) in polymer analysis. Simple caluclations permit easy determination of the effect of variables on the resolution. Through the use of two characterized polymer samples the specific resolutionRscan be calculated. From the specific resolution the percent of fractionation between any two or more populations can be predicted or, conversely, a GPC curve can be analyzed for the component molecular weights and molecular weight distributions MWD and then the per cent fractionation between the components calculated. This is especially useful in preparatory scale separations and purifications. The principle of the constancy of width divided by polydispersity,W/dis developed and used to demonstrate a very simple method of determining the polydispersity of a sample.

ISSN:0449-2994    

DOI:10.1002/polc.5070210105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractA new method of solving Tung's diffusion equation for gel permeation chromatography is presented. The method is based on the Fourier transform method for solving integral equations. Three examples (narrow, bimodal, and broad distributions) are used for illustrating the method of solution. A simple means of estimating the resolution factorhfor a multicolumn system, based on a knowledge of the resolution factorsh, for the individual columns and the gel permeation chromatograph piping system, is described and tested.

ISSN:0449-2994    

DOI:10.1002/polc.5070210106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractThe resolution power of gel permeation chromatography (GPC) columns and their combinations is tested as a function of the pore sizes of the gels and as a function of the elution velocity. The efficiency of GPC is characterized by the ratioUG/UT, whereUGis the experimental, andUTthe theoretical, inhomogeneity. The latter quantity is obtained from absolute measurements ofMw, andMn. The ratio passes through a minimum for a series of columns with increasing pore sizes. The minimum occurs at that column or column set which is best suited to resolving a given polymer.UG/UTfor any column decreases with decreasing elution velocity. At a certain velocityUG/UTbecomes 1. This velocity is usually smaller thanv= 1 ml./min., but for some columns appreciably greater. Columns with lowUG/UTvalues allow an unexpectedly good separation of mixtures of two polymers withMw/Mn= 2 andMw(I)/Mw(II) = 2. A compression effect toward the peaks of the two components is observed.

ISSN:0449-2994    

DOI:10.1002/polc.5070210107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractVarious gel permeation chromatography (GPC) factors affecting chromatogram interpretation have been studied. These include the variation of refractive index with polymer concentration and molecule size, the concentration effect, calibration curve selection, and column deterioration. Several assumptions inherent in GPC interpretation were found to be valid with reasonable limitations. The area under the GPC trace was found to be directly proportional to the weight of dissolved polymer, and the advantages of a method of calculating molecular weight averages by means of area rather than the conventional count height technique have been demonstrated. A synthetic broad distribution standard, composed of a wide molecular‐size range of narrow‐distribution standards, has been proposed for the diagnosis of the condition of GPC column syst

ISSN:0449-2994    

DOI:10.1002/polc.5070210108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractIn this paper we present a rigorous argument for the validity of a new technique for obtaining greatly increased resolution of the chromatograms of a gel permeation chromatograph. The method is phenomenological in that no assumptions are made about the separationprocess, although certain simple assumptions are made about the characteristics of this process. Instead, the method makes use of the observable behavior of narrow polymer fractions of presumably known composition. From a pragmatic point of view, this is an important aspect of the method, since the results predicted by the method depend only upon what the chromatograph is observed to do, and not upon what it is assumed to do. This method has been implemented in FORTRAN IV for the IBM 7094 computer.

ISSN:0449-2994    

DOI:10.1002/polc.5070210109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractThis paper reports a preliminary evaluation of four methods of correcting for imperfect resolution in gel permeation chromatography. These are methods of Tung, Smith, Hess and Kratz, and Pickett. To evaluate the methods over a range of resolutions, many broad‐ and narrow‐distribution polystyrene samples covering the molecular weight range 1000–500,000 were analyzed with three different column combinations having residence times from 20 to 150 min. The results show the increasing importance of the resolution correction with increasing molecular weight and decreasing residence times. For Tung's method the correction to molecular weight averages ranged from about 4% for 150 min. of residence time to about 12% for 20 min. Residence times as short as 10 or 15 min. should be possible without serious loss of accuracy. Inconsistencies in the high molecular weight results for the methods of Tung and Smith indicate inadequacies in the assumed chromatogram shapes for single molecular species, due to effects of column overloading and species interaction. These effects can be reduced by decreasing the sample concentration. When these effects are not prominent, the methods of Tung and Smith appear to be adequate. Smith's modified method permits the use of various chromatogram shapes for single species to account for overloading and interaction. Computational difficulties at present limit the use of the method of Hess and Kratz. Pickett's method looks promising, especially if concentration dependence can be included in the chromatograms representing the single species. Further evaluation needs to be done to determine which method best handles the region where overloading and species interaction

ISSN:0449-2994    

DOI:10.1002/polc.5070210110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractAlthough gel permeation chromatography (GPC) was developed primarily for measuring the molecular size distribution of polymers, it has been extremely useful for analyzing materials of intermediate and low molecular weight. It is also in this range that properties of compounds other than molecular size appear to have the greatest effect on the elution characteristics of solutes. Therefore, in order to increase the effectiveness of GPC as an analytical tool, the elution behavior of about 100 model compounds was studied and this information used to assist in the interpretation of chromatograms.

ISSN:0449-2994    

DOI:10.1002/polc.5070210111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractSpherical porous silica beads, a new material manufactured by Péchiney‐Saint‐Gobain, has been studied as a packing material for gel permeation chromatography columns. By choosing an appropriate pore size distribution, supports of good selectivity have been obtained. Universal calibration curves have been determined by plotting retention volumes for various polymer standards [polystyrene, poly(vinyl chloride), and dextran] against the logarithm of the productMw[n]. The nature of the polymer and the solvent (tetrahydrofuran or water) does not appear to affect much the calibration curve for a given support. Column efficiency was evaluated by measuring zone spreading as a function of column length, flow rate, and average particle diameter. The experimental results show that reproducible, uniform, and inherently efficient columns of good selectivity can be prepared with silica beads of average diameter, larger than 100 μ. In view of the observed decrease of efficiency loss at higher flow rates and of the relatively low pressure drop, porous silica beads appear to be a promising packing material for high‐speed analytical gel permeation chromat

ISSN:0449-2994    

DOI:10.1002/polc.5070210112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY