Retention mechanism of poly(ethylene oxide) in reversed-phase and normal-phase liquid chromatography

Cho, Dong−Hyun; Park, Soo‐Jin; Hong, Jeongmin; Chang, Taihyun

doi:10.1016/s0021-9673(02)01953-2

Cited by 62 publications

(46 citation statements)

References 38 publications

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“…In these cases, ÁH ad and ÁS ad must be positive and 0 < ÁH ad < TÁS ad from eq 5, though these were not observed directly. The similar result was observed in the RP-mode separation for PEO in the aqueous eluents by Cho et al 4 They obtained ÁH ad > 0 and ÁS…”

Section: Direction Of Temperature Gradient In Np-tgicsupporting

confidence: 87%

“…In the RP-mode, PEO samples in the aqueous eluents were separated with a negative temperature gradient. [2][3][4] In the NP-mode, PS samples in the organic eluents were separated with a negative temperature gradient, as reported in our previous paper. 6 In the present case, PMMA in System II was also separated with a negative temperature gradient.…”

Section: Direction Of Temperature Gradient In Np-tgicmentioning

confidence: 99%

“…The exception reported so far was a case where poly(ethylene oxide) (PEO) was fractionated using C18 bonded silica column and a mixture of acetonitrile and water by negative temperature gradient. [2][3][4] On the other hand, the results in the normal-phase mode TGIC (NP-TGIC) reported are not so many. However both temperature gradients were reported in NP-TGIC.…”

mentioning

confidence: 99%

“…However both temperature gradients were reported in NP-TGIC. That is, polystyrene (PS), 5,6 polyisoprene (PI), 5 PEO 4 and poly(2-vinylpyridine) (P2VP) 7 were separated by the positive temperature gradient, whereas PS samples were separated also by the negative temperature gradient using the respective columns of bare silica and NH 2 -modified silica packing materials and the eluent mixtures of chloroform and n-hexane (nHx) at the respective compositions in our previous work. 6 It was reported that the positive temperature dependencies of the retention were obtained for PS 8 and poly(styrene-co-methyl methacrylate) [P(S-co-MMA)] 9 in common organic eluents and also poly(ethylene glycol) in aqueous eluents.…”

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confidence: 99%

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Direction of Temperature Gradient and Retention Mechanism in Normal-Phase Temperature Gradient Interaction Chromatography for Poly(methyl methacrylate) Fractionation

Matsumoto

Kawai

Teramachi

2007

Polym J

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ABSTRACT:Temperature gradient interaction chromatography (TGIC) is a powerful technique for molecular characterization of polymers, in which the interaction strength is controlled by varying the column temperature. In the present paper, the direction of temperature gradient for normal-phase mode TGIC in poly(methyl methacrylate) (PMMA) fractionation was studied by using System I (column: cyano-modified silica == eluent: 1,4-dioxane/n-hexane) and System II (bare silica == 1,4-dioxane/CH 2 Cl 2 ), respectively. It was found that PMMA samples were separated by positive and negative temperature gradients using the respective systems. The results were also discussed theoretically. 1,2 TGIC separates polymer components in the order of molecular weight with a resolution superior to size exclusion chromatography (SEC). TGIC separation is driven mainly by adsorptive interaction between solutes and stationary phase and the strength of the interaction is controlled by varying the column temperature, to offset the molecular weight dependency of the adsorption strength. During the sample elution, the column temperature is varied continuously by positive (rising) or negative (lowering) temperature gradient. In many studies of TGIC, reversed-phase mode TGIC (RP-TGIC) has been applied to the separation of various polymers. In almost all cases of RP-TGIC, the positive temperature gradient was applied. The exception reported so far was a case where poly(ethylene oxide) (PEO) was fractionated using C18 bonded silica column and a mixture of acetonitrile and water by negative temperature gradient.2-4 On the other hand, the results in the normal-phase mode TGIC (NP-TGIC) reported are not so many. However both temperature gradients were reported in NP-TGIC. That is, polystyrene (PS), 5,6 polyisoprene (PI), 5 PEO 4 and poly(2-vinylpyridine) (P2VP) 7 were separated by the positive temperature gradient, whereas PS samples were separated also by the negative temperature gradient using the respective columns of bare silica and NH 2 -modified silica packing materials and the eluent mixtures of chloroform and n-hexane (nHx) at the respective compositions in our previous work. 6 It was reported that the positive temperature dependencies of the retention were obtained for PS 8 and poly(styrene-co-methyl methacrylate) [P(S-co-MMA)] 9 in common organic eluents and also poly(ethylene glycol) in aqueous eluents.10 If these systems were used for NP-TGIC, the negative temperature gradient should be effective. Then, it is very interesting whether not only low polar polymer PS but also high polar polymer poly(methyl methacrylate) (PMMA) can be separated by both of positive and negative temperature gradients in NP-TGIC. All cases of TGIC separation of PMMA samples reported so far were carried out by RP-mode using positive temperature gradient, as far as we know. However, PMMA samples and block copolymer samples involving PMMA block were separated mainly by NP-mode in the liquid chromatography at the critical condition (LCCC), 11,12 and the above mentio...

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Section: Direction Of Temperature Gradient In Np-tgicsupporting

confidence: 87%

Section: Direction Of Temperature Gradient In Np-tgicmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Direction of Temperature Gradient and Retention Mechanism in Normal-Phase Temperature Gradient Interaction Chromatography for Poly(methyl methacrylate) Fractionation

Matsumoto

Kawai

Teramachi

2007

Polym J

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“…[19][20][21][22][23][24] As shown in Eqs. (3a) to (3c), in a physical adsorption procedure, by the linear regression analysis of its enthalpy changes ∆H and entropy changes ∆S, the enthalpy-entropy compensation relationship and compensation temperatures T c can be separately obtained.…”

Section: Enthalpy-entropy Compensation and Compensation Temperature T Cmentioning

confidence: 99%

Thermodynamics and Extra‐thermodynamics of Bacillus subtilis α‐Amylase in Some Chromatographic Systems

et al. 2009

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The thermodynamics and extra-thermodynamics of Bacillus subtilis α-amylase in five kinds of chromatographic systems were studied by determining their adsorption equilibrium constant K SL , enthalpy change, entropy change, free energy change and compensation temperature under different temperature areas. The results showed that on an RP-C 18 reversed-phase medium, a Zn-chelated Sepharose fast-flow affinity medium and a WCX-1 cation-exchange medium, their ln K SL separately linearly changed with the reciprocal of absolute temperatures under two different temperature ranges of 13-30 and 30-50 ℃; and on PEG-400 and modified PEG-400 hydrophobic media, their ln K SL separately linearly decreased with the reciprocal of absolute temperatures under the temperature areas of 13-40 and 13-30 ℃, while when the temperatures were separately over 40 and 30 ℃, they violently decreased with the reciprocal of absolute temperatures. Through studying the relations among the enthalpy change, entropy change, free energy change and the conformational change of α-amylase under the different temperature areas, it was found that on the RP-C 18 reversed-phase medium and Zn-chelated Sepharose fast-flow affinity medium under the temperature range of 30-50 ℃ and on the WCX-1 cation-exchange medium under the temperature range of 13-30 ℃, their adsorption procedures were driven by both the enthalpy change and the entropy change; while on the Zn-chelated Sepharose fast-flow affinity medium under the temperature range of 13-30 ℃, on the WCX-1 cation-exchange medium under the temperature range of 30-50 ℃ and on the PEG-400 and modified PEG-400 hydrophobic media under the temperature range of 13-65 ℃, their adsorption procedures were driven only by the entropy change. Finally, by comparing the compensation temperatures of α-amylase in these chromatographic systems each other, it was further found that their enthalpy changes could be compensated only with their entropy changes rising from their conformational change.

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Separation of Polymers by Chromatography

Chang

2022

Macromolecular Engineering

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While mother nature can produce uniform macromolecules as found in many biological systems, man‐made polymers are hardly homogeneous. Synthetic polymers are usually complex mixtures of molecules differing in various molecular characteristics such as molecular weight (MW), chemical composition, functionality, microstructure, and chain architecture. For precise characterization of polymers, the multivariate distributions in all these molecular characteristics need to be measured, which is an extremely difficult task, if not impossible. In practice, however, it is often sufficient to analyze a limited number of molecular characteristics. For the purpose, liquid chromatography is the most widely used method that has made a remarkable progress during the last several decades in both instrumentation and understanding of the separation mechanism. Size exclusion chromatography (SEC) has been the most widely employed chromatographic separation technique for the characterization of synthetic polymers since its inception about a half‐century ago. Compared to traditional fractionation methods of polymers, SEC is an excellent method in precision, analysis speed, required amount of a sample, etc. Nonetheless, SEC separates the polymer molecules according to the chain size that depends on not only MW but also other molecular characteristics such as composition, chain architecture, and microstructure. Therefore, for instance, SEC cannot separate nonlinear homo‐polymers according to MW or copolymers according to the composition. In contrast to SEC in which the different pore‐accessibility of macromolecules is the main separation mechanism, interaction chromatography (IC) fractionates polymers according to the interaction strength between the polymer molecules and the sorbent. In results, IC is more sensitive to the chemical nature of the polymers than SEC. By judiciously selecting the IC separation condition, it is possible to separate polymers according to specific molecular properties with higher resolution than SEC. Furthermore, one can access to the chromatographic critical condition for a given polymer system by adjusting the solute interaction strength with the sorbent until the exclusion and interaction contributions to the solute retention are exactly compensated. At the critical condition, polymers of different MW coelute. Therefore, LC at the critical condition (LCCC) can be used as a unique tool for the characterization of polymers since one can suppress the peak dispersion by MW distribution and focus on other molecular characteristics. Recently, polymer separations using two‐dimensional LC by a rational combination of SEC, IC, or LCCC have become more and more popular for the characterization of polymers with multivariate distributions. In this article, chromatographic separation methods of synthetic polymers are reviewed with an emphasis on non‐SEC methods.

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Retention mechanism of poly(ethylene oxide) in reversed-phase and normal-phase liquid chromatography

Cited by 62 publications

References 38 publications

Direction of Temperature Gradient and Retention Mechanism in Normal-Phase Temperature Gradient Interaction Chromatography for Poly(methyl methacrylate) Fractionation

Direction of Temperature Gradient and Retention Mechanism in Normal-Phase Temperature Gradient Interaction Chromatography for Poly(methyl methacrylate) Fractionation

Thermodynamics and Extra‐thermodynamics of Bacillus subtilis α‐Amylase in Some Chromatographic Systems

Separation of Polymers by Chromatography

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