Cross-fractionation, chromatographic

Fig. 39. Cross-fractionation chromatograph of an ethylene-propylene sample. Reprinted From Ref. 86. Copyright (2001), with permission from Elsevier.

Glockner G (1991) Gradient HPLC of copolymers and chromatographic cross-fraction. Springer, Berlin Heidelberg New York... 

G. GlOckner, Gradient HPLC of Copolymers and Chromatographic Cross-fractionation, Springer-Verlag, Heidelberg (1991). 

Glockner, G. (1991). Gradient HPLC and Chromatographic Cross-Fractionation. Springer, Berlin, Heidelberg, New York. 

Multi-dimensional Chromatography. Multi-dimensional chromatography is the term used to describe a variety of methods where fractions from one chromatographic system are each transferred to another for further separation. Combinations of SEC with thin-layer chrcmatography have been shown to enable separation of copolymers by composition in a "cross-fractionation". OC utilizes a combination of two SECs in a cross-fractionation approach. 

Fig. 30. Chromatographic cross-fractionation of300 mg poly(styrene-6-methyl methacrylate) with 47 wt % styrene. SEC curves of the fractions obtained by column adsorption chromatography. The large SEC curve is from the non-fractionated sample. (From Ref.1321 with permission)...

Recently, chromatographic cross-fractionation of random poly(styrene-co-ethyl methacrylate) samples was carried out by the combination of SEC and TLC. The use of chromarods together with a flame ionization detector allowed the quantitative... 

Fig. 31. Chromatographic cross-fractionation of 0.87 mg poly(styrene-co-acrylonitrile). The sample was a mixture of 59.3 % copolymer with 16.1% AN and 40.7 % of another copolymer with 30 % AN. The latter produced the band at 15-20 min elution time, the former the band at about 9 min. SEC slices of 0.5 ml each as indicated in the upper right part of the figure. They were used without any additional treatment for the second separation. The molar mass data indicated refer to the shaded SEC slices1391.

Glockner, G., van den Berg, J. H. M., Meijerink, N. L., Scholte, T. G. Characterization of copolymers chromatographic cross-fractionation analysis of styrene-acrylonitrile copolymers , in Kleintjens, L., Lemstra, P. (ed) Integration of Fundamental Polymer Science and Technology , Elsevier Applied Science Publ., Barking, UK (1986), p. 85... 

Although this method is very time consuming, it can, in principle, be regarded as an alternative to the chromatographic cross fractionation to characterize copolymers and other complicated polyelectrolyte structures. 

By the use of different modes of liquid chromatography it is possible to separate polymers selectively with respect to hydrodynamic volume (molar mass), chemical composition or functionality. Using these techniques and combining them with each other or with a selective detector, two-dimensional information on different aspects of molecular heterogeneity can be obtained. If, for example, two different chromatographic techniques are combined in a cross-fractionation mode, information on CCD and MMD can be obtained. Literally, the term chromatographic cross-fractionation refers to any combination of chromato-... 

Balke ST, Patel RD (1983) Orthogonal chromatography. Polymer cross-fractionation by coupled gel permeation chromatographs. In Craver CD (ed) Polymer characterization. Adv Chem Ser 203, American Chemical Society, Washington, DC... 

This book covers some of the significant advances in hyphenated chromatographic separation methods for polymer characterization. Chromatographic separation techniques in this volume include size-exclusion chromatography, liquid chromatography, and field flow fractionation methods that are used in conjunction with information-rich detectors such as molecular size-sensitive or compositional-sensitive detectors or coupled in cross-fractionation modes. 

The method traditionally used for measuring the Bivariate Distribution is the "Chromatographic Cross Fractionation" (also referred to as "Two-dimensional Chromatography" or "Orthogonal Chromatography"). Macromolecules having different composition are separated in a silica column, and an SEC column is then used to elute chains having different sizes. ... 

Combination with other liquid chromatographic techniques is also reported by several workers. Orthogonal coupling of an SEC system to another high-performance liquid chromatography (HPLC) system K, Kj to achieve a desired cross-fractionation was proposed. It was an SEC-SEC mode, using the same polystyrene column, but the mobile phase in the first system was chosen to accomplish only a hydrodynamic volume separation, and the mobile phase in the second system was chosen so as to be a thermodynamically poorer solvent for one of the monomer types in the copolymer, in order to fractionate by composition under adsorption or partition modes as well as size exclusion. 

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