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Träfflista för sökning "L773:0021 9673 ;pers:(Nilsson Lars)"

Sökning: L773:0021 9673 > Nilsson Lars

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1.
  • Bolinsson, Hans, et al. (författare)
  • A novel method for calibration of AF4 channels for hydrodynamic radius determination : the nanoemulsion method (featuring MALS)
  • 2018
  • Ingår i: Journal of Chromatography A. - 0021-9673. ; 1533, s. 155-163
  • Tidskriftsartikel (refereegranskat)abstract
    • This study suggests a novel method for determination of the channel height in asymmetrical flow field-flow fractionation (AF4), which can be used for calibration of the channel for hydrodynamic radiusdeterminations. The novel method uses an oil-in-water nanoemulsion together with multi angle lightscattering (MALS) and elution theory to determine channel height from an AF4 experiment. The methodis validated using two orthogonal methods; first, by using standard particle elution experiments and, sec-ondly, by imaging an assembled and carrier liquid filled channel by x-ray computed tomography (XCT). It is concluded that the channel height can be determined with approximately the same accuracy aswith the traditional channel height determination technique. However, the nanoemulsion method canbe used under more challenging conditions than standard particles, as the nanoemulsion remains stablein a wider pH range than the previously used standard particles. Moreover, the novel method is also morecost effective.
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2.
  • Bolinsson, Hans, et al. (författare)
  • A novel method for calibration of AF4 channels for hydrodynamic radius determination : the nanoemulsion method (featuring MALS)
  • 2018
  • Ingår i: Journal of Chromatography A. - : Elsevier. - 0021-9673 .- 1873-3778. ; 1533, s. 155-163
  • Tidskriftsartikel (refereegranskat)abstract
    • This study suggests a novel method for determination of the channel height in asymmetrical flow field-flow fractionation (AF4), which can be used for calibration of the channel for hydrodynamic radiusdeterminations. The novel method uses an oil-in-water nanoemulsion together with multi angle lightscattering (MALS) and elution theory to determine channel height from an AF4 experiment. The methodis validated using two orthogonal methods; first, by using standard particle elution experiments and, sec-ondly, by imaging an assembled and carrier liquid filled channel by x-ray computed tomography (XCT). It is concluded that the channel height can be determined with approximately the same accuracy aswith the traditional channel height determination technique. However, the nanoemulsion method canbe used under more challenging conditions than standard particles, as the nanoemulsion remains stablein a wider pH range than the previously used standard particles. Moreover, the novel method is also morecost effective.
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3.
  • Bolinsson, Hans, et al. (författare)
  • An alternative method for calibration of flow field flow fractionation channels for hydrodynamic radius determination : The nanoemulsion method (featuring multi angle light scattering)
  • 2018
  • Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1533, s. 155-163
  • Tidskriftsartikel (refereegranskat)abstract
    • This study suggests a novel method for determination of the channel height in asymmetrical flow field-flow fractionation (AF4), which can be used for calibration of the channel for hydrodynamic radius determinations. The novel method uses an oil-in-water nanoemulsion together with multi angle light scattering (MALS) and elution theory to determine channel height from an AF4 experiment. The method is validated using two orthogonal methods; first, by using standard particle elution experiments and, secondly, by imaging an assembled and carrier liquid filled channel by x-ray computed tomography (XCT). It is concluded that the channel height can be determined with approximately the same accuracy as with the traditional channel height determination technique. However, the nanoemulsion method can be used under more challenging conditions than standard particles, as the nanoemulsion remains stable in a wider pH range than the previously used standard particles. Moreover, the novel method is also more cost effective.
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4.
  • Choi, Jaeyeong, et al. (författare)
  • Separation and zeta-potential determination of proteins and their oligomers using electrical asymmetrical flow field-flow fractionation (EAF4)
  • 2020
  • Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1633
  • Tidskriftsartikel (refereegranskat)abstract
    • Electrical asymmetrical flow field-flow fractionation (EAF4) is an interesting new analytical technique that separates proteins based on size or molecular weight and simultaneously determines the electrical characteristics of each population. However, until now, the research using EAF4 has not been published except for the proof-of-concept in the original publication by Johann et. al. in 2015 [1]. Hence the methods capabilities and optimized conditions need to be further investigated, such as composition of the carrier liquid, pH stability and effect of the electric field strength. The pH instability was observed in the initial method of EAF4 due to the electrolysis products when applied electric field. Therefore, we have investigated and provided a modified method for rapid pH stabilization through additional focusing step with the electric field. Then, the electrical properties such as the zeta-potential and effective net charge of the monomer and oligomers of three different proteins (GA-Z, BSA, and Ferritin) were determined based on their electrophoretic mobility from EAF4. The results showed that there were limitations to the applicability of separation by EAF4 to proteins. Nevertheless, this study shows that EAF4 is an interesting new technique that can examine the zeta-potential of individual proteins in mixtures (or monomers and oligomers) not accessible by other techniques.
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5.
  • Håkansson, Andreas, et al. (författare)
  • Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows : Part I. A theoretical approach
  • 2012
  • Ingår i: Journal of Chromatography A. - 0021-9673 .- 1873-3778. ; 1253, s. 120-126
  • Tidskriftsartikel (refereegranskat)abstract
    • Direct determination of hydrodynamic radius from retention time is an advantage of the field-flow fractionation techniques. However, this is not always completely straight forward since non-idealities exist and assumptions have been made in deriving the retention equations. In this study we investigate the effect on accuracy from two factors: (1) level of sophistication of the equations used to determine channel height from a calibration experiment and (2) the influence of secondary relaxation on the accuracy of hydrodynamic radius determination. A new improved technique for estimating the channel height from calibration experiments is suggested. It is concluded that severe systematic error can arise if the most common channel height equations are used and an alternative more rigorous approach is described. For secondary relaxation it is concluded that this effect increases with the cross-flow decay rate. The secondary relaxation effect is quantified for different conditions. This is part one of two. In the second part the determination of hydrodynamic radius are evaluated experimentally under similar conditions.
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6.
  • Håkansson, Andreas, et al. (författare)
  • Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows. Part 1. A theoretical approach.
  • 2012
  • Ingår i: Journal of chromatography. A. - : Elsevier BV. - 1873-3778 .- 0021-9673. ; 1253, s. 120-126
  • Tidskriftsartikel (refereegranskat)abstract
    • Direct determination of hydrodynamic radius from retention time is an advantage of the field-flow fractionation techniques. However, this is not always completely straight forward since non-idealities exist and assumptions have been made in deriving the retention equations. In this study we investigate the effect on accuracy from two factors: (1) level of sophistication of the equations used to determine channel height from a calibration experiment and (2) the influence of secondary relaxation on the accuracy of hydrodynamic radius determination. A new improved technique for estimating the channel height from calibration experiments is suggested. It is concluded that severe systematic error can arise if the most common channel height equations are used and an alternative more rigorous approach is described. For secondary relaxation it is concluded that this effect increases with the cross-flow decay rate. The secondary relaxation effect is quantified for different conditions. This is part one of two. In the second part the determination of hydrodynamic radius are evaluated experimentally under similar conditions.
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7.
  • Magnusson, Emma, et al. (författare)
  • Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows : Part II. Experimental evaluation
  • 2012
  • Ingår i: Journal of Chromatography A. - 0021-9673 .- 1873-3778. ; 1253, s. 127-133
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study we investigate the effect of programmed cross-flows on the error in the hydrodynamic radii (rh) determination with asymmetrical flow field-flow fractionation (AsFlFFF). Three different standard polystyrene particles (nominal radii of 30 and 40 and 50 nm) are fractionated with exponentially and linearly decaying cross-flows with different decay rates. Hydrodynamic radii are calculated according to retention theory including steric effects. Rapid decay is expected to give rise to systematic deviations in rh determination. The error in rh was found to be small when decay rates with half-lives longer than 6 min were used, whereas steeper decays could give rise to errors as high as 16% of the particle size. The error is often explained in terms of secondary relaxation. However, comparisons show that experimental errors are significantly larger than what would be expected due to secondary relaxation, suggesting that other factors also have to be considered in order to fully understand deviations for rapidly decaying cross-flow.
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8.
  • Magnusson, Emma, et al. (författare)
  • Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows : Part II. Experimental evaluation
  • 2012
  • Ingår i: Journal of Chromatography A. - : Elsevier. - 0021-9673 .- 1873-3778. ; 1253, s. 127-133
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study we investigate the effect of programmed cross-flows on the error in the hydrodynamic radii (rh) determination with asymmetrical flow field-flow fractionation (AsFlFFF). Three different standard polystyrene particles (nominal radii of 30 and 40 and 50 nm) are fractionated with exponentially and linearly decaying cross-flows with different decay rates. Hydrodynamic radii are calculated according to retention theory including steric effects. Rapid decay is expected to give rise to systematic deviations in rh determination. The error in rh was found to be small when decay rates with half-lives longer than 6 min were used, whereas steeper decays could give rise to errors as high as 16% of the particle size. The error is often explained in terms of secondary relaxation. However, comparisons show that experimental errors are significantly larger than what would be expected due to secondary relaxation, suggesting that other factors also have to be considered in order to fully understand deviations for rapidly decaying cross-flow.
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9.
  • Pérez-Rea, Daysi, et al. (författare)
  • Co-elution effects can influence molar mass determination of large macromolecules with asymmetric flow field-flow fractionation coupled to multiangle light scattering
  • 2017
  • Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1506, s. 138-141
  • Tidskriftsartikel (refereegranskat)abstract
    • Starch and hence, amylopectin is an important biomacromolecule in both the human diet as well as in technical applications. Therefore, accurate and reliable analytical methods for its characterization are needed. A suitable method for analyzing macromolecules with ultra-high molar mass, branched structure and high polydispersity is asymmetric flow field-flow fractionation (AF4) in combination with multiangle light scattering (MALS) detection. In this paper we illustrate how co-elution of low quantities of very large analytes in AF4 may cause disturbances in the MALS data which, in turn, causes an overestimation of the size. Furthermore, it is shown how pre-injection filtering of the sample can improve the results.
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10.
  • Zielke, Claudia, et al. (författare)
  • Co-elution phenomena in polymer mixtures studied by asymmetric flow field-flow fractionation
  • 2018
  • Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1532, s. 251-256
  • Tidskriftsartikel (refereegranskat)abstract
    • Most polymers generally have complex characteristics. Analysis and understanding of these characteristics is crucial as they, for instance, influence functionality. Separation and analysis of samples of polymers, biopolymers in particular, is challenging since they often display broad distributions in size, structure and molar mass (M) and/or a tendency to form aggregates. Only few analytical techniques are suitable for the task. AF4-MALS-dRI is highly suited for the task, but the analysis can nevertheless be especially challenging for heterogeneous mixtures of polymers that exhibit wide size distributions or aggregation. For such systems, systematic and thorough method development is clearly a requirement. This is the purpose of the present work, where we approach the problem of heterogeneous polymer samples systematically by analyzing mixtures of two different polymers which are also characterized individually. An often observed phenomenon in AF4 of samples with a high polydispersity is a downturn in M vs. elution time, especially common at high retention. This result is often dismissed as an artifact attributed to various errors in detection and data processing. In this work, we utilize AF4-MALS-dRI to separate and analyze binary mixtures of the well-known polysaccharides pullulan and glycogen, or pullulan and poly(ethylene oxide), respectively, in solution. The results show that an observed downturn – or even an upturn – in M can be a correct result, caused by inherent properties of the analyzed polymers.
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