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Retention mechanism of fatty alcohol ethoxylates in reversed-phase liquid chromatography SCIE SCOPUS

Title
Retention mechanism of fatty alcohol ethoxylates in reversed-phase liquid chromatography
Authors
Cho, DHong, JPark, SChang, T
Date Issued
2003-02-07
Publisher
ELSEVIER SCIENCE BV
Abstract
Fatty alcohol ethoxylates (FAEs) are widely used nonionic surfactants that have distributions in both alkyl and poly(ethylene oxide) (PEO) chain length. Generally, two-dimensional liquid chromatography technique is required for the complete characterization of both distributions. By selecting a proper stationary and mobile phase condition, however, we can obtain fully resolved chromatograms of a FAE sample (Brij 30) with respect to both alkyl and PEO chain length by using a single reversed-phase C-18 column and aqueous acetonitrile mobile phase. FAEs show a peculiar reversed-phase liquid chromatography (RPLC) retention behavior with an aqueous-organic mobile phase, the retention mechanism of which has not been fully elucidated. For a fixed alkyl chain length, FAEs with higher-molecular-mass PEO block elutes first and the van't Hoff plot of the retention factor shows a curvature. The unique retention behavior can be understood from the opposite thermodynamic characteristics associated with RPLC retention of PEO block and alkyl chain: the sorption process of PEO to the non-polar stationary phase shows DeltaHdegrees>0 and DeltaSdegrees>0 while the alkyl chain shows DeltaHdegrees<0 and DeltaSdegrees<0 in contrast. The relative magnitude of the two contributions can change the elution order of the FAE. Therefore the often found, inverted elution order of FAEs (the early elution of FAEs with longer PEO block) is due to the positive enthalpic interaction of PEO blocks, which is a characteristic of the hydrophobic interaction. And-the curvature of the van't Hoff plots was analyzed assuming the temperature dependent thermodynamic variables. (C) 2002 Elsevier Science B.V. All rights reserved.
Keywords
retention mechanism; temperature effects; fatty alcohol ethoxylates; alcohol ethoxylates; ethoxylates; EXCLUSION-ADSORPTION CHROMATOGRAPHY; GRADIENT INTERACTION CHROMATOGRAPHY; NONIONIC SURFACTANTS; HYDROPHOBIC INTERACTION; ISOCRATIC SEPARATION; MASS-SPECTROMETRY; BEHAVIOR; POLYISOPRENE; MACROMOLECULES; QUANTITATION
URI
https://oasis.postech.ac.kr/handle/2014.oak/18709
DOI
10.1016/S0021-9673(02)01956-8
ISSN
0021-9673
Article Type
Article
Citation
JOURNAL OF CHROMATOGRAPHY A, vol. 986, no. 2, page. 199 - 206, 2003-02-07
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장태현CHANG, TAIHYUN
Div of Advanced Materials Science
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