Nonstandard Methods Based on Size Exclusion Chromatography Principles

Belen'kii, B.G.; Gankina, E.S.; Kasalainen, G. E.; Tennikov, M.B.

doi:10.1021/bk-1996-0635.ch016

Cited by 21 publications

(27 citation statements)

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“…The column 250 x 4 mm was packed with Nucleosil (bare silica gel), pore size 12 nm, particle 3 x 250 x 4 mm was applied. The detector signal was collected on-line by using a PC and Waters Baseline data acquisition system (Milford, MA, U.S.A.).…”

Section: Methodsmentioning

confidence: 99%

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Separation of Poly(methyl methacrylate)s According to Their Tacticity II. Chromatographic Investigations of Poly(methyl methacrylate)s with Different Tacticity at the Critical Adsorption Point

Berek

Jančo

Hatäda

et al. 1997

Polym J

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ABSTRACT:The poly(methyl methacrylate)s (PMMAs) differing in their tacticity were investigated by liquid chromatography at the critical adsorption point (LC CAP). The set of chromatographic conditions (eluent composition determining its adsorption strength, column packing nature and temperature) was identified for given highly stereoregular PMMAs, under which the exclusion of polymer chain from the pores (entropic effect) was just compensated by the adsorption of the polymer chain on the column packing surface (enthalpic effect). The result was that no separation according to the solute molar mass took place. Using bare silica gel column packing and tetrahydrofuran (THF)/n-hexane mixture as eluent at 30°C, syndiotactic (st-) PMMAs were more readily adsorbed on the column packing surface than isotactic (it-) PMMAs. The critical adsorption point (CAP) for st-PMMAs was reached with the eluent composition THF/n-hexane (83.2/16.8, w/w). Under the same conditions, however, it-PMMAs were eluted in the size exclusion chromatography (SEC) mode and the separation was achieved for mixtures of it-PMMA and st-PMMA of lower molar mass. With the same bare silica gel as the stationary phase and chloroform (CHC13)/ethanol or CHCl3/THF mixtures as eluents at 30°C, st-PMMAs were less adsorbed on column packing and they eluted in the SEC mode while the CAP was reached for it-PMMAs, i.e., CHC13/ethanol (97.2/2.8, w/w) or CHCl3/THF (87.7/12.3, w/w). By using latter non-aggregating mixed eluents containing chloroform, the satisfactory separation ofst-plus it-PMMA mixtures were achieved even for polymers with molar masses exceeding IOOOOOgmol-1 . The results indicate the potential of liquid chromatographic procedures that combine exclusion and adsorption mechanisms in separation of macromolecules according to their stereoregularity. Further, the advantages of the LC CAP mixed eluents is demonstrated that are composed solely of the solvents for polymers under study.KEY WORDS Poly(methyl methacrylate) / Tacticity / Isotactic Poly(methyl methacrylate) / Syndiotactic Poly(methyl methacrylate) / Liquid Chromatography at Critical Adsorption Point / Separation /

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Section: Methodsmentioning

confidence: 99%

“…3 LC CAP presents a combination of size exclusion (entropic) separation mechanism with adsorption (enthalpic) separation mechanism. A set of the chromatographic conIn the present work we have tested the potentiality of the LC CAP in separation ofpoly(methyl methacrylate)s (PMMAs) with different tacticity.…”

mentioning

confidence: 99%

Separation of Poly(methyl methacrylate)s According to Their Tacticity II. Chromatographic Investigations of Poly(methyl methacrylate)s with Different Tacticity at the Critical Adsorption Point

Berek

Jančo

Hatäda

et al. 1997

Polym J

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“…The distribution coefficient K d is unity, regardless of the size of the macromolecules, and all macromolecules of equal chemical structure elute from the chromatographic column in one peak. To describe this phenomenon the term "chromatographic invisibility" is used, meaning that the chromatographic behavior is not directed by the size but by the inhomogeneities (chemical structure) of the macromolecules [96][97][98][99][100][101][102][103].…”

Section: Coupling Of Liquid Chromatography At the Critical Point Of Amentioning

confidence: 99%

Hyphenated Techniques in Liquid Chromatography of Polymers

Pasch

2000

New Developments in Polymer Analytics I

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Complex polymers are distributed in more than one direction of molecular heterogeneity. In addition to the molar mass distribution, they are frequently distributed with respect to chemical composition, functionality, and molecular architecture. For the characterization of the different types of molecular heterogeneity it is necessary to use a wide range of analytical techniques. Preferably, these techniques should be selective towards a specific type of heterogeneity. The combination of two selective analytical techniques is assumed to yield two-dimensional information on the molecular heterogeneity.The present review presents the principle ideas of combining different analytical techniques in two-dimensional analysis schemes. Most promising protocols for hyphenated techniques refer to the combination of two different chromatographic methods and the combination of chromatography and spectroscopy. This review will discuss the basic principles of two-dimensional chromatography and the hyphenation of liquid chromatography with selective detectors.

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“…Russian scientists using TLC [1][2][3] and later LC [4,5] have been the first experimentally identify critical conditions. At the critical conditions polymers of a given kind are eluted independently from their molar mass (for example, Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Pioneers of the critical conditions have recognized the universal character of this phenomenon in chromatography of polymers and they have experimentally demonstrated that critical conditions represent a natural connection between the [6] adsorption and exclusion modes of polymer separation [1,2,4,5]. They have found its "critical" sensitivity to variation of experimental variables, such as mobile phase composition, temperature, pressure and column packing as well as to chemical differences of macromolecules [1][2][3][4][5]7]. Scientists from St. Petersburg have also elucidated the theoretical foundation of critical phenomenon [5,[8][9][10][11] for review see [12].…”

Section: Introductionmentioning

confidence: 99%

Liquid Chromatography under Critical and Limiting Conditions: A Survey of Experimental Systems for Synthetic Polymers

Macko

Hunkeler

2003

Liquid Chromatography / FTIR Microspectroscopy / Microwave Assisted Synthesis

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At the interface between the entropic size exclusion separation and the enthalpydominated liquid adsorption chromatography it is possible, experimentally, to identify conditions where polymer samples elute independent of their molar mass. These "critical conditions" function according to theory by compensating the entropy and enthalpy of the separation. For a series of common and specialty polymers, the mobile phase compositions and temperature which provide the molar mass independent elution behavior, for a given stationary phase, have been extracted from literature and summarized herein. This collection may help to select, or forecast, suitable LC systems, when an application of liquid chromatography under critical conditions for a polymer is required. Correlations between properties of solvents, sorbents and polymers, such as solubility parameters, eluotropic strength and Mark-Houwink constants have been extracted from the collected data. Specifically, solubity parameters of critical mobile phases corresponding to a pair polymer-sorbent are in a majority of cases very similar. The elution strength of the first component of a critical binary eluent correlates linearly with the volume percent of the second component, especially, when an identical silica gel is applied. However, the critical conditions are independent of the thermodynamic quality of the solvent. Under limiting conditions, the mobile phase may be even a precipitant or a strong adsorption promoting liquid for an injected polymer. Possibilities for increase of the upper molar mass separation limit are outlined and influence of sample solvent on elution behavior is described. Applications of liquid chromatography under conditions of enthalpy-entropy compensation for separation of homo-and copolymers are also, briefly, summarized.

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Nonstandard Methods Based on Size Exclusion Chromatography Principles

Cited by 21 publications

References 0 publications

Separation of Poly(methyl methacrylate)s According to Their Tacticity II. Chromatographic Investigations of Poly(methyl methacrylate)s with Different Tacticity at the Critical Adsorption Point

Separation of Poly(methyl methacrylate)s According to Their Tacticity II. Chromatographic Investigations of Poly(methyl methacrylate)s with Different Tacticity at the Critical Adsorption Point

Hyphenated Techniques in Liquid Chromatography of Polymers

Liquid Chromatography under Critical and Limiting Conditions: A Survey of Experimental Systems for Synthetic Polymers

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