| 1. |
- Kempe, Henrik, et al.
(författare)
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Determination of diffusion coefficients of proteins in stationary phases by frontal chromatography
- 2006
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 93:4, s. 656-664
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Tidskriftsartikel (refereegranskat)abstract
- A strategy to determine effective diffusion coefficients of proteins in chromatographic gels is presented in this article. An experimental methodology based on frontal liquid chromatography was combined with a numerical methodology based on a mathematical model describing the chromatographic process including the extra-column dispersion, the dispersion due to the packed bed, the external mass transfer from the bulk phase to the stationary phase, and the diffusive transport within the stationary phase. The methodology has several advantages compared to previously reported methods to determine diffusion coefficients in that no other equipment than an HPLC is required, any class of stationary phases can be investigated as long as the experiments are performed under non-binding conditions, and no modification, e.g., moulding of slabs or membranes, to the stationary phase is required. To show the applicability of the methodology, the effective diffusion coefficients of lysozyme, bovine serum albumin, and immunoglobulin gamma in Sepharose (TM) CL-4B were determined and shown to be comparable with those determined with other methods. (c) 2005 Wiley Periodicals, Inc.
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| 2. |
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| 3. |
- Persson, Patrik, et al.
(författare)
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A methodology for estimation of mass transfer parameters in a detailed chromatography model based on frontal experiments
- 2004
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Ingår i: Chemical Engineering Research & Design. - : Elsevier BV. - 0263-8762. ; 82:A4, s. 517-526
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Tidskriftsartikel (refereegranskat)abstract
- A methodology for estimation of the unknown physical parameters in a detailed model for chromatographic processes is proposed. The model describes the concentration of the solute in the mobile phase and considers external/internal mass transfer resistance. The external volume and its mixing effect are also considered. The unknown model parameters estimated are the bed void, the axial dispersion coefficient, the liquid film mass transfer coefficient, the effective diffusion coefficient and the apparent bead porosity. All the parameters in the model were subsequently determined in three classes of experiments, the external mixing behaviour, the mobile phase behaviour and the stationary phase behaviour. The estimates are based on the sum of the least squares of the residuals between the experimental breakthrough curves and the model response. The methodology is exemplified by frontal experiments with lysozyme, bovine serum albumin and immuno globulin gamma on a well-defined column set-up. When the mixing properties in the external volume had to be accounted for, to avoid adding broadening behaviour to the dispersion coefficient, the film mass transfer coefficient and the diffusion coefficient were also investigated. The results show that it is possible to estimate the unknown parameters using the proposed methodology.
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| 4. |
- Persson, Patrik, et al.
(författare)
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Characterization of a continuous supermacroporous monolithic matrix for chromatographic separation of large bioparticles
- 2004
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 88:2, s. 224-236
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Tidskriftsartikel (refereegranskat)abstract
- A continuous supermacroporous monolithic chromatographic matrix has been characterized using a capillary model, experimental breakthrough curves, and pressure drop experiments. The model describes the convective flow and its dispersive mixing effects, mass transfer resistance, pore size distribution, and the adsorption behavior of the monolithic matrix. It is possible to determine an effective pore size distribution by fitting the capillary model to experimental breakthrough curves and pressure drop experiments. The model is able to describe the flow rate dependence of the experimental breakthrough curves. Mass transport resistance was due to: (i) dispersive mixing effects in the convective flow in the pores; and (ii) slow diffusion in the stagnant film covering the surface within each pore, under adsorption conditions. The monolithic matrix can be described by a very narrow pore size distribution, illustrating one of the advantages of the gel. A broader pore size distribution results in increased band broadening. This can be studied easily using the model developed in this investigation. (C) 2004 Wiley Periodicals, Inc.
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| 5. |
- Persson, Patrik, et al.
(författare)
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Estimation of adsorption parameters in a detailed affinity chromatography model based on shallow bed experiments
- 2005
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1873-3298 .- 1359-5113. ; 40:5, s. 1649-1659
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Tidskriftsartikel (refereegranskat)abstract
- A method for estimation of unknown adsorption parameters in a detailed chromatography model including the Langmuir adsorption expression is proposed. The model describes the concentration of the solute in the mobile phase and considers extemal/intemal mass transfer resistance and adsorption dynamics. The external volume and its mixing effect are also considered. The unknown model parameters estimated are the bed void, the axial dispersion coefficient, the liquid film mass transfer coefficient, the effective diffusion coefficient, the apparent bead porosity, the adsorption/desorption rate coefficients and the Langmuir isotherm. All the parameters in the model were subsequently determined in four classes of experiments, the external mixing behaviour, the mobile phase behaviour, the stationary phase behaviour and the adsorption behaviour. The estimates are based on the sum of the least squares of the residuals between the experimental breakthrough curves and the model response. The methodology is exemplified by frontal experiments with bovine serum albumin in a shallow packed bed. The results show that it is possible to estimate the adsorption parameters using the proposed methodology, and to replace the Langmuir adsorption dynamic expression with the corresponding isotherm when high inlet concentrations are used. It was also investigated at what inlet concentration this model simplification resulted in satisfactory results. It was possible to estimate adsorption parameters using several experimental breakthrough curves simultaneously, i.e. multiple data responses, to obtain single parameters that are valid within the interval of inlet concentrations used. (c) 2004 Elsevier Ltd. All rights reserved.
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| 6. |
- Persson, Patrik, et al.
(författare)
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Parameter estimation of protein chromatographic processes based on breakthrough curves
- 2002
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Ingår i: Computer Applications in Biotechnology 2001 (CAB8). - 0080436811 ; , s. 113-118
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Konferensbidrag (refereegranskat)abstract
- A methodology for parameter estimation in chromatographic models is suggested in this paper, which is based on breakthrough curves from a given column set-up. Physical parameters are found in two subsequent experiments, one for the mobile phase behaviour and one for the stationary phase behaviour. The estimations are based on flow rate changes and multiple responses. Adsorption parameters are found also in two subsequent experiments, one for isotherm parameters and one for kinetics parameters. These estimations are based on concentration changes. The conclusion is that it is possible to estimate the parameters in a general rate model using nonlinear least square estimation and numerical simulation of the model. Copyright (C) 2001 IFAC.
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| 7. |
- Årzén, Karl-Erik, et al.
(författare)
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Integrated Control and Scheduling
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The report gives a state-of-the-art survey of the field of integrated control and scheduling. Subtopics discussed are implementation and scheduling of periodic control loops, scheduling under overload, control and scheduling co-design, dynamic task adaptation, feedback scheduling, and scheduling of imprecise calculations. The report also presents the background, motivation, and research topics in the ARTES project Integrated Control and Scheduling.
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