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  Estimation of single solute adsorption isotherms applying the nonlinear frequency response method using non-optimal frequencies

Ilic, M., Petkovska, M., & Seidel-Morgenstern, A. (2008). Estimation of single solute adsorption isotherms applying the nonlinear frequency response method using non-optimal frequencies. Journal of Chromatography A, 1200(2), 183-192. doi:10.1016/j.chroma.2008.05.063.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-0013-9519-8 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0014-B5A1-1
Genre: Journal Article


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Ilic, M.1, Author              
Petkovska, M.2, Author
Seidel-Morgenstern, A.1, 3, Author              
1Physical and Chemical Foundations of Process Engineering, Max Planck Institute for Dynamics of Complex Technical Systems, Max Planck Society, ou_1738150              
2Faculty of Technology and Metallurgy, Department of Chemical Engineering, Belgrade, Serbia, ou_persistent22              
3Otto-von-Guericke-Universität Magdeburg, External Organizations, ou_1738156              


Free keywords: Adsorption isotherms; Liquid chromatography; Nonlinear frequency response; Higher order frequency response functions; Parameter estimation
 Abstract: In order to estimate single solute adsorption isotherms, the nonlinear frequency response (FR) of a chromatographic column is analyzed experimentally and evaluated using the concept of higher order frequency response functions (FRFs) based on the Volterra series and generalized Fourier transform. In this case study, it has been investigated the adsorption of ethyl benzoate on octadecyl silica from a mixture of methanol and water (60:40) as a solvent. Experiments are performed using a standard gradient HPLC unit. For estimation of adsorption isotherms by the nonlinear FR method the column inlet concentration is changed in a nearly sine waveform around several steady-state concentrations. Using this method the first three local derivatives of a single solute adsorption isotherm are estimated from the low frequency asymptotes of the corresponding functions, i.e. the phase and first order derivative of the FRFs. For an accurate estimation of isotherm coefficients periodical experiments should be preformed for frequencies below a certain critical frequency. This is the frequency needed for approaching the low frequency asymptotic behaviour of the corresponding functions close enough, so that errors due to the non-feasibility of experiments with zero frequency can be neglected. Unfortunately, depending on the properties of the system, it can happen (as for the system investigated here) that experiments for the critical frequency would be too long and cannot be realized. In order to study the loss of accuracy of the nonlinear FR method, when it is applied for non-optimal frequencies, experiments are performed for frequencies approximately one order of magnitude higher than the critical frequency required to evaluate the FRF phases. The obtained isotherm model coefficients are compared with the ones estimated using conventional frontal analysis as a reference method. The isotherms determined by two methods are similar, however a closer look reveals that peaks predicted under overloading conditions differ. Copyright © 2008 Elsevier B.V. All rights reserved. [accessed July 2, 2008]


Language(s): eng - English
 Dates: 2008
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Method: -
 Identifiers: eDoc: 362958
DOI: 10.1016/j.chroma.2008.05.063
Other: 15/08
 Degree: -



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Title: Journal of Chromatography A
Source Genre: Journal
Publ. Info: Amsterdam : Elsevier
Pages: - Volume / Issue: 1200 (2) Sequence Number: - Start / End Page: 183 - 192 Identifier: ISSN: 0021-9673
CoNE: /journals/resource/954925527837_1