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  • 1.
    Altun, Zeki
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    New Techniques for Sample Preparation in Analytical Chemistry: Microextraction in Packed Syringe (MEPS) and Methacrylate Based Monolithic Pipette Tips2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Sample preparation is often a bottleneck in systems for chemical analysis. The aim of this work was to investigate and develop new techniques to address some of the shortcomings of current sample preparation methods. The goal has been to provide full automation, on-line coupling to detection systems, short sample preparation times and high-throughput.

    In this work a new technique for sample preparation that can be connected on-line to liquid chromatography (LC) and gas chromatography (GC) has been developed. Microextraction in packed syringe (MEPS) is a new solid-phase extraction (SPE) technique that is miniaturized and can be fully automated. In MEPS approximately 1 mg of sorbent material is inserted into a gas tight syringe (100-250 μL) as a plug. Sample preparation takes place on the packed bed. Evaluation of the technique was done by the determination of local anaesthetics in human plasma samples using MEPS on-line with LC and tandem mass spectrometry (MS-MS). MEPS connected to an autosampler was fully automated and clean-up of the samples took about one minute. In addition, in the case of plasma samples the same plug of sorbent could be used for about 100 extractions before it was discarded.

    A further aim of this work was to increase sample preparation throughput. To do that disposable pipette tips were packed with a plug of porous polymer monoliths as sample adsorbent and were then used in connection with 96-well plates and LC-MS-MS. The evaluation of the methods was done by the analysis of local anaesthetics lidocaine and ropivacaine, and anti-cancer drug roscovitine in plasma samples. When roscovitine and lidocaine in human plasma and water samples were used as model substances, a 96-plate was handled in about two minutes. Further, disposable pipette tips may be produced at low cost and because they are used only once, carry-over is eliminated.

  • 2.
    Altun, Zeki
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Andersson, Lars I.
    AstraZeneca R&D Södertälje, DMPK & BAC, Södertälje, Sweden.
    Blomberg, Lars G.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Abdel-Rehim, Mohamed
    Karlstad University, Division for Business and Economics.
    Some Factors Affecting the Performance of Microextraction in Packed Syringe (MEPS)Manuscript (Other academic)
  • 3.
    Anukam, Anthony
    et al.
    Univ Ft Hare, South Africa.
    Meyer, Edson
    Univ Ft Hare, South Africa..
    Okoh, Omobola
    Univ Ft Hare, South Africa..
    Mamphweli, Sampson
    Univ Ft Hare, South Africa..
    Gasification characteristics of sugarcane bagasse2012In: PROCEEDINGS OF SAIP2012: THE 57TH ANNUAL CONFERENCE OF THE SOUTH AFRICAN INSTITUTE OF PHYSICS / [ed] J. J. VanRensburg, SOUTH AFRICAN INST PHYSICS , 2012, p. 464-471Conference paper (Refereed)
    Abstract [en]

    Sugarcane bagasse is a residue that results from the crushing of sugarcane in the sugar industry. Among the various agricultural crop residues, sugarcane bagasse is the most abundant lignocellulosic material in tropical and sub-tropical countries including South Africa. Bagasse is a renewable feedstock that can be used for power generation and manufacturing cellulosic ethanol In the sugarcane industries the bagasse is mainly burnt inefficiently in boilers that provide the heating for the industry. This project seeks to investigate the possibility of gasifying sugarcane bagasse as an efficient conversion technology. Proximate and ultimate analysis of sugarcane bagasse was conducted after which the results were used to conduct computer simulation of the mass and energy balance during gasification. This paper presents the proximate and ultimate analysis as well as the computer simulation results.

  • 4.
    Bohlin, Maria E.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Method development for affinity capillary electrophoresis of ß2-glycoprotein I and biological ligands2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The final goal of this study is to establish a microscale analysis method that allows solution phase characterization of interactions between β2-glycoprotein I (β2gpI) and some of its ligands. Human β2gpI is a phospholipid- and heparin-binding plasma glycoprotein. The physiological role of the protein in normal blood coagulation is not entirely known, nor is its role in autoimmune diseases characterized by blood clotting disturbances (thrombosis). Quantitative binding data of β2gpI interactions with some of its ligands may help elucidating the mechanisms behind these diseases and in the development of new approaches for diagnostics, prevention, and therapy.

    In this thesis, capillary electrophoresis (CE) was used as methodological platform for the interaction studies. The analysis of peptides and proteins by CE is desirable due to low sample consumption, possibilities for non-denaturing and highly effective separations. The first objective of this thesis was to find an approach to prevent charge dependent adsorption of β2gpI to the inner surface of the capillaries. Analyte adsorption at the negatively charged inner surface of fused silica capillaries is detrimental to interaction analyses. This phenomenon is especially pronounced in the analysis of basic proteins and proteins containing exposed positively charged domains, such as β2gpI. A new strategy to suppress these solute-wall interactions was devised, investigated and optimized. This strategy exploits the pH hysteresis behavior of fused silica surfaces, by simply performing an acidic pretreatment of the capillary. The results in this thesis show that the acidic pretreatment efficiently prevents protein adsorption.

  • 5.
    Bohlin, Maria E
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Blomberg, Lars G.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Heegaard, Niels H H
    Statens Serum Institut, Copenhagen.
    Effects of ionic strength, temperature and conformation on affinity interactions of β2-glycoprotein I monitored by capillary electrophoresis2011In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 32, p. 728-737Article in journal (Refereed)
    Abstract [en]

    We have used CE to evaluate the interaction between β2-glycoprotein I (β2gpI) and heparin. β2gpI is a human plasma protein involved in the blood coagulation cascade. It is of interest to functionally characterize the interactions of β2gpI because the exact function is not entirely known and because circulating autoantibodies against β2gpI are associated with an increased risk of thrombotic events.

     

    The effect of the ionic strength, temperature, and conformation of the protein on the interaction between β2gpI and heparin has been studied. The CE procedure for this study is simple, fast and automatic. β2gpI and heparin were allowed to interact during electrophoresis at different ionic strength buffers and at different capillary temperatures. To mimic perturbation of the conformation of β2gpI, different denaturing agents (SDS, ACN and urea) were added to the background electrolyte. While simple 1:1 binding isotherms were obtained at 22 °C the data strongly suggests that at physiological temperature the binding stoichiometry is not 1:1 and/or that cooperative interactions begin to play a role. We found that (i) the KD values differed by a factor of 60 at the ionic strengths studied (ii) β2gpI was resistant to denaturation with SDS and ACN, but was partially denatured by urea and (iii) the KD for the β2gpI-heparin interaction in the presence of urea was 10 times higher than the KD determined at the same conditions without urea added. Therefore, we conclude that the interaction between β2gpI and heparin is dependent on electrostatic interactions and on the conformation of β2gpI. 

  • 6.
    Bohlin, Maria E.
    et al.
    Karlstad University, Division for Chemistry.
    Blomberg, Lars G.
    Karlstad University, Division for Chemistry.
    Heegard, Niels H.H.
    Department of Autoimmunology, Statens Serum Institut, Copenhagen.
    Utilizing the pH hysteresis effect for versatile and simple electrophoretic analysis of protein in bare fused-silica capillaries2005In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 26, no 21, p. 4043-4049Article in journal (Refereed)
  • 7.
    Bohlin, Maria E.
    et al.
    Karlstad University, Division for Chemistry.
    Kogutowska, Ewa
    Department of Autoimmunology, Statens Serum Institut, Copenhagen.
    Blomberg, Lars G.
    Karlstad University, Division for Chemistry.
    Heegaard, Niels H.H.
    Department of Autoimmunology, Statens Serum Institut, Copenhagen.
    Capillary electrophoresis-based analysis of phospholipid and glycosaminoglycan binding by human β2-glycoprotein I2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1059, p. 215-222Article in journal (Refereed)
  • 8.
    Charcot, Maxime
    1997.
    Study of solar cells films with a Duetta fluorometer2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 9.
    Dabrowski, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Rening av rökgaskondensat i ett fjärrvärmeverk: Återanvändning av rökgaskondensat som spädvatten2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Arvika Fjärrvärme AB is manufacturing and distributing district heating to around 300 customers in Arvika. Heat production consists of a BFB boiler fed with GROT fuel (branches and peaks) and delivers a maximum power of 30 MW. In order to operate the plant, an average of 60 m3 of water per day is consumed from the urban water network. The water consumption is divided between water treatment, sooting and process cooling.

    In the processes, sulfur is dosed to obtain a more complete combustion of the hazardous flue gases that can occur. This is a result of previous thesis made for Arvika fjärrvärme. GROT is a fuel that contains high levels of moisture, which means that a high amount of condensate is formed during combustion, averaging 100 m3 per day. At present, condensate is sufficient to meet the condensate limit values ​​to be flushed into the drain. This is achieved by sand filtration and pH neutralization.

    Today, Arvika heat production is equipped with a purification stage for the feed water consisting of a softening filter and membrane filtration. This creates good conditions for cleaning the condensate and recirculating it in the process. Questions for this study are which hazardous substances the condensate can contain and how the condensate composition affected due to sulfur dosage. In addition, Arvika fjärrvärme wants to find out whether the purified condensate can replace the use of the urban water and, finally, if the condensate can be purified and used as feed water in the process.

    The execution of the work was based on a full-scale attempt in two operating cases of 9 and 18 MW. The tank collecting all condensate after purification in the sand filter and pH neutralization was coupled to the feed water purification stage. Thus, the condensate was pumped and purified in the softening filter and membrane filter. Assay substrates were collected before and after purification of the condensate.

    In addition to the topics that Arvika investigates, high levels of alkalinity were found in the condensate. The sulfur dosage that Arvika technology works with can be the cause of the high concentrations of sulphate. However, it appears that both the sulfate and alkalinity were purified in the membrane filter.

    The amount of condensate formed cannot completely replace the entire water requirement, but definitely large parts. The condensate can be used as feed water based on the retention rate for all substances. However, it appears that two substances, chloride and sulphate can create problems for the membrane filter. To investigate this, the condensate should be tested over a longer period of time to see the affect the chloride as well as the sulphate in the long run.

  • 10.
    Edström, Emelie
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Solvent adsorption in SFC: Adsorption of methanol under supercritical conditions2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Chromatography is a widely used separation technique including many different modes, for example supercritical fluid chromatography (SFC) which uses a supercritical fluid as mobile phase. A supercritical fluid is achieved when a substance is subjected to a temperature and pressure above the critical point and the boundary between the liquid phase and gas phase is erased. The interest for SFC has increased in recent years, mainly for separation of chiral molecules in the pharmaceutical industry. What makes SFC interesting is that it is a quick, cost-efficient and green method. This is in part due to less organic solvent used in the mobile phase in SFC compared with liquid chromatography and that the carbon dioxide that represents the major part of the mobile phase is a by-product from other processes.

    In SFC modifiers, often small alcohols, are added to carbon dioxide based mobile phase in order to increase the solubility of polar compounds. In this study the adsorption of methanol to two different stationary phases; Kromasil-Diol and chiral Lux Cellulose-4 were studied. Adsorption is a phenomenon where surface interactions crate a higher density of molecules at the surface than in the bulk.

    The aim of this work has been to study the adsorption of modifier (methanol) to the stationary phase both to determine the extent of adsorption and the kinetics for system equilibration. These findings were then put into perspective of normal use of SFC for separation of molecules.

    There are a number of techniques for measuring adsorption; in this study the tracer pulse method is used. This is a pulse method where a concentration plateau is created and an isotope labelled molecule is injected. This was performed in the mobile phase composition from pure carbon dioxide to pure methanol. In addition to the tracer pulse experiments the isotope effect, the eluent flow, equilibration times for the column and retention times for a set of analytes were measured. For the Diol column no large isotope effect was observed, the method was also proved to be highly reproducible since several runs gave consistent results. Calculations based on the experimental data showed that a 6.3 Å thick layer was built up at a methanol fraction of 13% (v/v), corresponding to a monolayer. Changes of the methanol fraction below the saturation level has has greater effect on the retention factor for the analytes than at higher methanol fractions, when the monolayer was saturated. The conclusion of this is that SFC is more stable in the area where the layer has been built up.

    A preliminary study has been made for the chiral Lux Cellulose-4 column which was not as conclusive as for the Kromasil-Diol column. This type of column needs further studies to confirm the deviating observations and to investigate the cause for these.

  • 11.
    Enmark, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Fundamental Investigations of Supercritical Fluid Chromatography2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis aims at a deeper understanding of Supercritical Fluid

    Chromatography (SFC). Although preparative SFC has started to replace Liquid Chromatography (LC) in the pharmaceutical industry - because of its advantages in speed and its less environmental impact - fundamental understanding is still lacking. Therefore there is no rigid framework to characterize adsorption or to understand the impact of changes in operational conditions.

     

    In Paper I we demonstrated, after careful system verification, that most methods applied to determine adsorption isotherms in LC could not be applied directly in SFC. This was mainly due to operational differences and to the fact that the fluid is compressible which means that everything considered constant in LC varies in SFC.

     

    In Paper II we showed that the most accurate methods for adsorption isotherm determination in LC, the so called plateau methods, do not work properly for SFC. Instead, methods based on overloaded profiles should be preferred.

     

    In Paper III a Design of Experiments approach was successfully used to quantitatively describe the retention behavior of several solutes and the productivity of a two component separation system. This approach can be used to optimize SFC separations or to provide information about the separation system.

     

    In Paper IV severe peak distortion effects, suspected to arise from injection solvent and mobile phase fluid mismatches, were carefully investigated using experiments and simulations. By this approach it was possible to examine the underlying reasons for the distortions, which is vital for method development.

     

    Finally, in Paper V, the acquired knowledge from Paper I-IV was used to perform reliable scale-up in an industrial setting for the first time. This was done by carefully matching the conditions inside the analytical and preparative column with each other. The results could therefore provide the industry with key knowledge for further implementation of SFC.

  • 12.
    Enmark, Martin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    A thermodynamic and kinetic study of an unusual adsorption behavior-Methyl Mandelate on commercially available Tris-(3,5- dimethylphenyl)carbamoyl Cellulose Chiral Stationary Phase2012Conference paper (Other academic)
    Abstract [en]

    The adsorption equilibria of racemic methyl mandelate on a tris-(3,5- dimethylphenyl)carbamoyl cellulose chiral stationary phase (CSP) was investigated. The following were observed, the less retained enantiomer shows “Langmuirian” (type I) adsorption behavior, while the adsorption isotherm of the more retained compound contained an inflection point at low concentration. To analyze these differences, adsorption isotherms were determined and further analyzed using Scatchard plots and adsorption energy distribution (AED) calculations. The less retained enantiomer was best described by heterogeneous unimodal adsorption model (Tóth) while the second enantiomer was best described with a heterogeneous adsorption model with adsorbate-adsorbate interactions (bi-Moreau). The adsorption behavior of both enantiomers was also studied at several different temperatures and it was found to be exothermic; in addition, the non-idealadsorbate-adsorbate interaction strength decreases with increasing temperature. Stochastic analysis of the adsorption process could identify a single kinetic site for each enantiomer. The average amount of adsorption/desorption events increases and the sojourn time decreases with increasing temperature. This is an industrial – academic cooperation in the Fundamental Separation Science Group www.separationscience.se

  • 13.
    Enmark, Martin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    On the Reproducibility between Different Modern Supercritcal Fluid Chromatographic Systems2013Conference paper (Other academic)
    Abstract [en]

    Three different, commercially available, Supercritical Fluid Chromatography (SFC) systems were investigated: Thar Super Pure Discovery Series SFC, Waters UPC2 and Agilent 1260 Infinity SFC. The reason for choosing the two analytical systems from Agilent and Waters is that they represent two of the latest commercial systems available while the semi-preparative instrument was added to widen the study to include instruments also used for preparative purposes. With identical operational conditions set these systems were used to acquire analytical retention data and adsorption isotherms from overloaded injections. The investigation was limited to the use of methanol as modifier and operational conditions, temperature and back pressure most typically observed when utilizing SFC to separate polar compounds. The results clearly show that both analytical retention times and elution profiles are system dependent. Since the overloaded elution profiles are system dependent the adsorption isotherm will also be different. However, this do not mean that the adsorption is different, instead this it is due to the fact that identical instrumental settings, especially pressure and modifier composition settings, does not necessarily mean that the conditions inside the column are identical. This means that it is not possible to transfer an established separation method from one system to another, even if one is using the same column and identical instrument settings. Understanding of SFC-systems will be of fundamental importance for successful transfer of methods between systems, reliable adsorption isotherm determination, and analytical quality work and scaling up from analytical to preparative mode. These issues can probably be solved by measuring mass flow, pressure and temperature along the column, together with a sound understanding of the density variations of the mobile phase. However, the work of finding acceptable applications or guidelines to remove the tedious need for these measurements is currently investigated in our lab. This is a contribution from the Fundamental Separation Science Group www.FSSG.se

  • 14.
    Enmark, Martin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Using Modern SFC Systems for Adsorption Characterization2013Conference paper (Other academic)
    Abstract [en]

    Recently the pharmaceutical industry has started to replace preparative HPLC with preparative SFC to lower the environmental impact and to increase performance. Reliable characterization of the adsorption processes in SFC is therefore of utmost importance. The key thermodynamic phase system information is obtained by rigorous determination of adsorption isotherm data over a broad concentration range. If properly processed, this data gives not only correct information about the degree of heterogeneity but also the energy of interactions and mono layer capacities of each individual type of adsorption site in the phase system. Ultimately, this can result in identification of the types of interactions, i.e., dipole-dipole, van der Waals interactions etc. In this study we will present transfer of selected adsorption characterization methods, traditionally applied with success in LC, to SFC. We have here transferred all available knowledge from LC – from model selection to validation. We will also, using recent findings, explain the effects of pressure and temperature variations as well as how to accurately measure the volumetric flow rate on a modern analytical SFC system. We will demonstrate how the latest SFC instruments, with some critical modifications; have the potential for rapid and reliable acquisition of thermodynamic data using the ECP method. Finally we will elaborate on how the adsorption depends on density, temperature and modifier content in the mobile phase. This is a contribution from the Fundamental Separation Science Group www.FSSG.se

  • 15.
    Enmark, Martin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Enantioseparation of omeprazole effect of different packing particle size on productivity2012In: Journal of Chromatography A, ISSN 0021-9673, Vol. 1240, no 1, p. 123-131Article in journal (Refereed)
    Abstract [en]

    Enantiomeric separation of omeprazole has been extensively studied regarding both product analysis and preparation using several different chiral stationary phases. In this study, the preparative chiral separation of omeprazole is optimized for productivity using three different columns packed with amylose tris (3,5-dimethyl phenyl carbamate) coated macroporous silica (5, 10 and 25 Όm) with a maximum allowed pressure drop ranging from 50 to 400 bar. This pressure range both covers low pressure process systems (50–100 bar) and investigates the potential for allowing higher pressure limits in preparative applications in a future. The process optimization clearly show that the larger 25 Όm packing material show higher productivity at low pressure drops whereas with increasing pressure drops the smaller packing materials have substantially higher productivity. Interestingly, at all pressure drops, the smaller packing material result in lower solvent consumption (L solvent/kg product); the higher the accepted pressure drop, the larger the gain in reduced solvent consumption. The experimental adsorption isotherms were not identical for the different packing material sizes; therefore all calculations were recalculated and reevaluated assuming identical adsorption isotherms (with the 10 Όm isotherm as reference) which confirmed the trends regarding productivity and solvent consumption.

  • 16.
    Enmark, Martin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Högblom, Joakim
    Eka Chemicals.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Adsorption Isotherm Determination for Reliable Phase System Characterization in SFC: Challenges and Pitfalls2012Conference paper (Refereed)
    Abstract [en]

    Recently the pharmaceutical industry has started to replace HPLC with SFC because of incentives to lower the environmental impact and as well as increasing performance. Reliable characterization of the adsorption processes in SFC, is therefore of utmost importance. The key thermodynamic phase system information is obtained by rigorous determination of adsorption isotherms over a broad concentration range. If properly processed, this data gives not only correct information about the degree of heterogeneity but also the values of the energy of interactions and monolayer capacities of each individual type of adsorption site in the phase system; ultimately, this can result in identification of the types of interactions (dipole-dipole, van der Waals interactions etc.). In this study, we will present the transfer of LC adsorption characterization methods to SFC conditions using several model compounds with several different methods for adsorption isotherm determination traditionally applied with success in LC, and now modified for SFC. We have limited our investigation to methanol as modifier and used the operational conditions, temperature and backpressure most typically observed in industrial settings; in addition, we have used commercial standard SFC-equipment. The results clearly shows that adsorption isotherm determinations in SFC are considerably more complicated than in LC; we will go through the most important pitfalls and give guidelines for more rigorous determinations of adsorption data in SFC. This is an industrial – academic cooperation in the Fundamental Separation Science Group www.separationscience.se

  • 17.
    Enmark, Martin
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Undin, Torgny
    Uppsala University Analytisk Kemi.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Characterization of an unusual adsorption behavior of racemic methyl-mandelate on a tris-(3,5-dimethylphenyl) carbamoyl cellulose chiral stationary phase2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 38, p. 6688-6696Article in journal (Refereed)
    Abstract [en]

    An interesting adsorption behavior of racemic methyl mandelate on a tris-(3,5-dimethylphenyl)carbamoyl cellulose chiral stationary phase was theoretically and experimentally investigated. The overloaded band of the more retained enantiomer had a peculiar shape indicating a type V adsorption isotherm whereas the overloaded band of the less retained enantiomer had a normal shape indicating a type I adsorption behavior. For a closer characterization of this separation, adsorption isotherms were determined and analyzed using an approach were Scatchard plots and adsorption energy distribution (AED) calculations are combined for a deeper analysis. It was found that the less retained enantiomer was best described by a Tóth adsorption isotherm while the second one was best described with a bi-Moreau adsorption isotherm. The latter model comprises non-ideal adsorbate–adsorbate interactions, providing an explanation to the non-ideal adsorption of the more retained enantiomer. Furthermore, the possibility of using the Moreau model as a local model for adsorption in AED calculations was evaluated using synthetically generated raw adsorption slope data. It was found that the AED accurately could predict the number of adsorption sites for the generated data. The adsorption behavior of both enantiomers was also studied at several different temperatures and found to be exothermic; i.e. the adsorbate–adsorbate interaction strength decreases with increasing temperature. Stochastic analysis of the adsorption process revealed that the average amount of adsorption/desorption events increases and the sojourn time decreases with increasing temperature.

  • 18.
    Enmark, Martin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Åsberg, Dennis
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Shalliker, Andrew
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    A closer study of peak distortions in supercritical fluid chromatography as generated by the injection2015In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1400, p. 131-139Article in journal (Refereed)
    Abstract [en]

    Abstract In SFC the sample cannot be dissolved in the mobile phase, so it is often dissolved in pure modifier, or another liquid, sometimes resulting in serious distortions of the eluted peak profiles already at moderately high injection volumes. It is suspected the reasons for these effects are solvent strength mismatch and/or viscosity mismatch. This study presents a systematic and fundamental investigation of the origin of these peak deformations due to the injection solvent effects in SFC, using both systematic experiments and numerical modeling. The first set of experiments proved that the injection volume and the elution strength of the sample solution had a major impact of the shapes of the eluted peaks. Secondly, the sample band elution profile was numerically modeled on a theoretical basis assuming both un-retained and retained co-solvent injection plugs, respectively. These calculations quantitatively confirmed our first set of experiments but also pointed out that there is also an additional significant effect. Third, viscous fingering experiments were performed using viscosity contrast conditions imitating those encountered in SFC. These experiments clearly proved that viscous fingering effects play a significant role. A new method for determination of adsorption isotherms of solvents was also developed, called the “Retention Time Peak Method” (RTPM). The RTPM was used for fast estimation of the adsorption isotherms of the modifier and required using only two experiments.

  • 19.
    Eriksson, Björn
    Karlstad University, Division for Chemistry.
    In-line application of electric fields in capillary separation systems2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The magnitude of an electric field possible to apply in a capillary separation system is limited, because a high electric field causes a too high current through the capillary. Application of the electric field in-line will give an increased conductivity in the column, further increasing the risk of too high currents. The conductivity changes were found to result from an overall increase in ionic strength within the electric field. The increase in ionic strength is caused by the increase in mobile phase ions with electrophoretic velocity against the flow, together with OH- or H3O+ ions (depending on polarity) formed at the inlet electrode. Further it was found that the use of a pressurized reservoir or splitting of the flow at the inlet electrode could significantly limit the conductivity changes and thereby the maximum applicable electric field strengths could be increased.

  • 20.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Peterson, Patrik
    Astrazeneca.
    Edström, Lena
    Uppsala Universitet.
    Samie, Farzad
    Astrazeneca.
    Tatterton, Stephen
    Clarke, Adrian
    Astrazeneca.
    Why UHPLC Produces More Tailing Peaks Than HPLC, Why it Does Not Matter and How it Can be Addressed2012Conference paper (Refereed)
    Abstract [en]

    The purpose of this study is to demonstrate, with experiments and with computer simulations based on a firm chromatographic theory, that the wide spread perception of that the United States Pharmacopeia tailing factor must be lower than 2 (Tf < 2) is questionable when using the latest generation of LC equipment. It is shown that highly efficient LC separations like those obtained with sub-2 ÎŒm porous and 2.7 ÎŒm superficially porous particles (UHPLC) produce significantly higher Tf -values than the corresponding separation based on 3 ÎŒm porous particles (HPLC) when the same amount of sample is injected. Still UHPLC separations provide a better resolution to adjacent peaks. Expressions have been derived that describe how the Tf-value changes with particle size or number of theoretical plates. Expressions have also been derived that can be used to scale the injection volume based on particle size or number of theoretical plates to maintain the Tf-value when translating a HPLC separation to the corresponding UHPLC separation. An aspect that has been ignored in previous publications. Finally, data obtained from columns with different age/condition indicate that Tf-values should be complemented by a peak width measure to provide a more objective quality measure.

  • 21.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Peterson, Patrik
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Karlsson, Anders
    Astrazeneca.
    HPLC vs UHPLC - a comparison of peak asymmetry and plan to step forward using Quality by Design (QbD) related to analytical methods2012Conference paper (Refereed)
    Abstract [en]

    The purpose of this study is to demonstrate, with experiments and with computer simulations based on a firm chromatographic theory, that the wide spread perception of that the United States Pharmacopeia tailing factor must be lower than 2 (Tf < 2) is questionable when using the latest generation of LC equipment. It is shown that highly efficient LC separations like those obtained with sub-2 m porous and 2.7 m superficially porous particles (UHPLC) produce significantly higher Tf-values than the corresponding separation based on 3 m porous particles (HPLC) when the same amount of sample is injected. Still UHPLC separations provide a better resolution to adjacent peaks. Expressions have been derived that describe how the Tf-value changes with particle size or number of theoretical plates. Expressions have also been derived that can be used to scale the injection volume based on particle size or number of theoretical plates to maintain the Tf-value when translating a HPLC separation to the corresponding UHPLC separation. This aspect has been ignored in previous publications. Finally, data obtained from columns with different age/condition indicate that Tf-values should be complemented by a peak width measure to provide a more objective quality measure. A plan to take a further step for using Quality by Design (QbD) related to analytical methods will also be presented [Ref 1]. Continuous improvement of an original HPLC method to an UHPLC method will be the used as a case study. The capability of the two methods will be deeply studied using mechanistic comparisons. Method criteria that must be fulfilled for the two chromatographic methods will be stated. [1] 2012 PDA Europe Workshop Quality by Design The Role of Analytical Science in Implementing QbD − Technical and Regulatory Aspects, Liverpool UK 6-7 March. This is an industrial – academic cooperation in the Fundamental Separation S

  • 22.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    A more reliable procedure for estimating interactions between drugs and biomolecules using biosensors: a comparison with chromatography2012Conference paper (Other academic)
    Abstract [en]

    This poster serves as background information to the corresponding lecture. Adsorption isotherms are essential in order to understand the interaction between small molecules such as pharmaceutical compounds and larger biomolecules. An adsorption isotherm describes the relationship of free substance in a solution with adsorbed substance to a surface, at a specific and constant temperature. Adsorption isotherms could be determined using several different method, all method have their pros and cons. In this study we are using two modern but principally different biosensors to determine interactions: quarts micro-balance (QCM) and Surface plasmon resonance (SPR) to determine interactions. For a long time adsorption isotherms has been determined solely by the chromatographic community. In this study we will present transformation of adsorption analysis tools from chromatography to biosensors, especially calculation of adsorption energy distribution prior adsorption model fit. We will also discuss how the experiments should be conducted. Guidelines will be given for the experimental setup and for when the chromatographic or a biosensor technique is to be preferred. This is a contribution from the Fundamental Separation Science Group in Karlstad www.separationscience.se

  • 23.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Insights into retention mechanisms and bio-molecular interactions gained from rigorous evaluation of adsorption data derived from HPLC and modern biosensors2012Conference paper (Refereed)
    Abstract [en]

    The estimation of reliable adsorption / equilibrium data are crucial for researchers in a wide range of fields such as analytical chemistry, biochemistry, chemical engineering, pharmacology and pharmacokinetics. Traditionally, equilibrium data are simply estimated from the statistically best-fitted model to adsorption data; but there are many dangerous pitfalls on this road. We have therefore recently improved several methods for adsorption isotherm determinations. As example, the accuracy of generating adsorption data by the elution by characteristic points (ECP) method was increased considerably by a new experimental approach that eliminated the post-loop dispersion; the method was also expanded to cover more different general types of adsorption isotherms than before. We have also made important improvements on the processing and evaluation of the data based on a firm theoretical basis. In this context, a new numerical tool was developed, calculation of the adsorption energy distribution (AED) allowing the estimation of the degree of heterogeneity of the interaction prior to the rival model fit. This concept has also been transposed to modern biosensors such as surface plasmon resonance (SPR) technology and continuous flow quartz crystal microbalance (QCM). We have utilized the improvements of generating and evaluation adsorption data to reveal more detailed information about molecular interactions in systems aimed at analytical and preparative separations and to understand better bio-molecular interactions derived from modern biosensors. This is a contribution from the Fundamental Separation Science Group in Karlstad www.separationscience.se

  • 24.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Transposing Advanced LC Theory to Modern Biosensors - Estimation of Bio-Molecular Interactions and Drug-Protein Interactions by Transposing LC-Theory to Biosensors2012Conference paper (Other academic)
    Abstract [en]

    This poster will also serves as background information to the lecture “Deeper insights in retention mechanisms and molecular interactions through improved methods for generating and evaluation adsorption data”. Adsorption isotherms are essential in order to understand the interaction between small molecules such as pharmaceutical compounds and larger biomolecules. An adsorption isotherm describes the relationship of free substance in a solution with adsorbed substance to a surface, at a specific and constant temperature. Adsorption isotherms could be determined using several different method, all method have their pros and cons. In this study we are using two modern but principally different biosensors to determine interactions: quarts micro-balance (QCM) and Surface plasmon resonance (SPR) to determine interactions. For a long time adsorption isotherms has been determined solely by the chromatographic community. In this study we will present transformation of adsorption analysis tools from chromatography to biosensors, especially calculation of adsorption energy distribution prior adsorption model fit. We will also discuss how the experiments should be conducted. Guidelines will be given for the experimental setup and for when the chromatographic or a biosensor technique is to be preferred. This is a contribution from the Fundamental Separation Science Group in Karlstad www.separationscience.se

  • 25.
    Fornstedt, Torgny
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Åsberg, Dennis
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Lesko, Marek
    Rzeszow University of Technology.
    Enmark, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Forssén, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Kaczmarski, Krzysztof
    Rzeszow University of Technology.
    New Procedure for Predictions of Overloaded Profiles in Gradient Elution2013Conference paper (Other academic)
    Abstract [en]

    To simulate the separation process in liquid chromatography, the competitive adsorption isotherms need to be known. In gradient elution, the adsorption isotherms are determined with isocratic experiments on different mobile-phase plateaus, levels covering the range used in the gradient program. This can lead to extreme retention times for some mobile-phase compositions and therefore it might even be impossible to determine all necessary adsorption data using the traditional isocratic approach. In this talk, we will present a method where single and competitive nonlinear adsorption isotherms are determined directly from overloaded elution profiles in gradient elution. The numerical coefficients in the adsorption isotherms are determined by the inverse method that minimizes the difference between calculated and experimental elution profiles. This is a new method where the need for tedious/impossible isocratic experiments is eliminated. The method is systematically verified using both synthetic and experimental data. Finally the new method is used to successfully predict elution profiles for a two-component mixture in gradient elution. The new method open up the opportunity to study the adsorption of substances whose retention factor vary strongly with the mobile-phase composition, like peptides and proteins, where the classic methods will fail. We also intend to transfer the metholology for SFC in near future; but there are some problems to be solved first (see our SFC posters). This is a contribution from the Fundamental Separation Science Group www.FSSG.se

  • 26.
    Forss, Erik
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    On-line HPLC2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to increase the analysis frequency and thereby achieve a better understanding of the kinetics and dynamics of the chemical process without increasing the workload of the already strained analytical laboratory at Cambrex Karlskoga AB, this projects goal was to investigate whether a crude prototype for mobile on-line HPLC-analysis with automatic sampling and dilution could be built based on certain flow-injection analysis techniques. It was possible to achieve dilution with good repeatability even though saturation effects in the filter proved problematic. Separation and dilution of a binary mixture was also successful as proof-ofconcept.

  • 27.
    Forssén, Patrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    Uppsala University.
    Lämmerhofer, Michael
    Institute of Pharmaceutical Sciences, University of Tübingen, Germany.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Karlsson, Anders
    Department of Molecular Biology, Göteborg University .
    Lindner, Wolfgang
    Department of Analytical Chemistry, University of Vienna, Austria.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Uppsalas universitet.
    Optimization strategies accounting for the additive in preparative chiral liquid chromatography2012In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1269, p. 279-286, article id SIArticle in journal (Refereed)
    Abstract [en]

    This study is an in-depth investigation on how numerical optimization strategies that also account forthe additive type and concentration, in preparative batch chromatography, should be performed. As amodel system, the separation of Z-(R,S)-2-aminobutyric acid enantiomers on a quinidine carbamate-based chiral stationary phase in polar organic mode was used, with different additive strengths of aceticacid or hexanoic acid in methanol. The inverse method was used to determine the competitive adsorp-tion isotherm parameters for the enantiomers and the additives. Three different optimization strategieswere examined: (1) injection volume optimization, (2) optimization of injection volume and additiveconcentration, and (3) full optimization including injection volume, additive concentration, sample con-centration and flow rate. It was concluded that (i) it is important to incorporate the additive concentrationin the optimization procedure to achieve the highest production rates, (ii) the full optimization strategyhad the overall best results, and (iii) the selection of additive is very important (here acetic acid additivewas superior to the hexanoic acid additive). By including the additive in the adsorption model and inthe numerical optimization it is not only possible to achieve higher production rates but also to properlyselect the additive that is most advantageous for the specific separation problem.

  • 28.
    Forssén, Patrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    Uppsala University.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Injection profiles in liquid chromatography II: Predicting accurate injection-profiles for computer-assisted preparative optimizations2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 34, p. 5794-5800Article in journal (Refereed)
    Abstract [en]

    In computer assisted optimization of liquid chromatography it has been known for some years that it is important to use experimental injection profiles, instead of rectangular ones, in order to calculate accurate elution bands. However, the incorrectly assumed rectangular profiles are still mostly used especially in numerical optimizations. The reason is that the acquisition of injection profiles, for each injection volume and each flow rate considered in a computer-assisted optimization requires a too large number of experiments. In this article a new function is proposed, which enables highly accurate predictions of the injection profiles and thus more accurate computer optimizations, with a minimum experimental effort. To model the injection profiles for any injection volume at a constant flow rate, as few as two experimental injection profiles are required. If it is desirable to also take the effect of flow rate on the injection profiles into account, then just two additional experiments are required. The overlap between fitted and experimental injection profiles at different flow rates and different injection volumes were excellent, more than 90%, using experimental injection profiles from just four different injection volumes at two different flow rates. Moreover, it was demonstrated that the flow rate has a minor influence on the injection profiles and that the injection volume is the main parameter that needs to be accounted for.

  • 29.
    Forssén, Patrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Relative importance of column and adsorption parameters on the productivity in preparative liquid chromatography. I: Investigation of a chiral separation system2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1299, p. 58-63Article in journal (Refereed)
    Abstract [en]

    Starting out from an experimental chiral separation system we have used computer simulations for a systematic investigation on how the maximum productivity depends on changes in column length, packing particle size, column efficiency, back pressure, sample concentration/solubility, selectivity, retention factor of the first eluting component and monolayer saturation capacity. The study was performed by changing these parameters, one at a time, and then calculating the corresponding change in maximum productivity. The three most important parameters for maximum production rate was found to be (i) the selectivity (ii) the retention factor of the first eluting component and (iii) the column length. Surprisingly, the column efficiency and sample concentration/solubility were of minor importance. These findings can be used as rough guidelines for column selection, e.g. a low-efficiency column are more likely perform better, in terms of productivity, than a high-efficiency column that have higher retention factor for the first eluting component.

  • 30. Glenne, Emelie
    et al.
    Lesko, Marek
    Samuelsson, Jörgen
    Fornstedt, Torgny
    Impact of Methanol Adsorption on Robustness in Supercritical Fluid ChromatographyManuscript (preprint) (Other academic)
  • 31. Glenne, Emelie
    et al.
    Samuelsson, Jörgen
    Leek, Hanna
    Forssén, Patrik
    Klarqvist, Magnus
    Fornstedt, Torgny
    Systematic investigations of peak deformations due to amine additives in supercritical fluid chromatographyManuscript (preprint) (Other academic)
  • 32.
    Hoang, Xuan Huyen Trang
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Sample preparation and calibration in chromatographic analysis of natural products2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Gas chromatography and high performance liquid chromatography are common techniques to analyse many type of samples. Sample preparation is the first step and play an important role in the process of quantitative analysis. Sample preparation can have a major effect in the overall accuracy and reliability of the results. The aim of this step is to provide a sample aliquot that will not damage the column or instrument, have appropriate concentration, and is compatible with the intended analytical method. In the process of sample preparation and analysis, different errors may influence the results. Internal standards are usually used to limit these errors. The data in report I and II shows that the internal standard has helped to reduce errors due to sample preparation and the factors affecting results such as variations in injection volumes, evaporation of solvent and instability in detection.

  • 33.
    Höglund, Elisabeth
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    En jämförelse mellan industriellt och laborativt kokad pappersmassa med olika analytiska metoder: - innefattande utformning av en metod för enzymatisk nedbrytning av massafibrer2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The properties of industrially produced pulp and corresponding cooked pulp devised in the laboratory were studied during the first part of this project. The industrial pulp proved to have a lower surface charge compared to the laboratory-cooked pulp, while similar results were obtained during total charge analysis. Regarding properties such as fiber width and fiber length, no major differences between the pulps were found, and during the analysis of the total content of individual monosaccharides, only the amount of xylose differed showing a slightly lower amount for the laboratory-cooked pulp. Part two of the project included a method formation for analyzing the carbohydrate composition on the surface of pulp fibers. The sample containing polysaccharides was hydrolyzed with a mixture of cellulase and hemicellulase which resulted in gradual fiber peeling. The method itself may in fact need further development, but overall the test generated a positive outcome. To desalinate and lower the content of sugars within the enzyme mix before hydrolysis along with using calibration solutions containing enzymes were shown to be important factors in retaining optimal results.

  • 34.
    Ismailov, Taner
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Quantification of resin acids, fatty acids and sterols in process and waste water from forest industry2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This work focuses on wood extractives in effluents from the CTMP plant at Skoghall Mill. Pulp and paper industry effluents contain mostly natural compounds which are part of the trees. They are toxic to aquatic life but harmless in nature, as they are present in low concentrations. Processing tons of wood, such as in a pulp mill, strongly increases the concentrations of the toxic compounds (Ali, M. and Sreekrishnan, T., 2001) which have to be treated before transferring to the aquatic environment.Extractives can be found in different forms, as micelles soluble in water, unprocessed in fibers or absorbed on the surface of fibers. It is important to know in which forms extractives are mostly present in the effluent, so that they can be treated more efficiently. It is desired to have extractives absorbed on the fibers and fibrils present in the waste water, so they can be separated from the water and treated separately, e.g. burned for energy recovery. Dissolved extractives complicate the oxygen transfer in an aerated biological treatment step with their surface active properties (Sandberg, 2012).The aim of this study is quantification of extractives on the fibers suspended in the waste water and extractives dissolved in the water. The distribution between the two forms is an important input when designing future effluent treatment. Wood extractives itself are a wide group with different compounds. This work focuses on the main groups present in waste water: resin acids, free and esterified fatty acids and, free and esterified sterols. These groups are analyzed in different process waters and waste water before the waste water treatment plant. The measured concentrations of extractives were as expected, higher in process and effluent waters, lower in white water. Most of the extract was dissolved in the water and unfortunately fiber samples contained very low concentration from the total extract in the samples.

  • 35.
    Jonsson, Alexander
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Investigation of pore size effects at separation of oligonucleotides using Ion-pair RP HPLC: Examining of how the particle pore size of the stationary phase affects separations of oligonucleotides in therapeutic range2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Oligonucleotides may become a new class of therapies with the potential of curing many today untreatable diseases. Oligonucleotides becomes increasingly more difficult to separate with an increase in length since the relative difference in retention of these very similar compounds becomes increasingly smaller. Therefore, coelution of impurities formed during synthesis may result in insufficient purity, which is necessary for therapeutic treatments. Oligonucleotides are also relatively large biomolecules, possibly consisting of hundreds of nucleotides. As a result, oligonucleotides may have limited diffusion through the stationary phase pores which affects separation performance. Surprisingly few studies have be published in this research area and a wider knowledge in how this affects separation is needed. In this master thesis, separation of deoxythymidine oligonucleotides with 5-30 mers in length were separated with 60, 100, 200 and 300 Å pore size reversed phase C4 columns. It was concluded that pore size resulted in more restricted diffusion if insufficient pore size was used. Poor peak performance was also observed with too large pore sizes which lead to less efficient separations.

  • 36.
    Jonsson, Ann-Sofie
    Karlstad University, Division for Chemistry.
    Development and Validation of a Liquid Chromatography-Tandem Mass Spectrometry Method for Determination of Cyclosporine A in Whole Blood2009Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cyclosporine A (CsA) is a cyclic undecapolypeptide of fungal origin (Tolypocladium inflatum Gams). It has a molecular weight of 1202.6 Da and is used as an immunouppressive drug to prevent rejection of transplanted organs and bone marrow, and for the treatment of graft-versus-host disease. CsA exhibits a narrow therapeutic range between efficacy and toxicity. There are many side effects exerted by the drug and some of them are serious, such as renal dysfunction and increased risk of developing diabetes and malignant diseases such as lymphoma. In addition, the inter-individual and intra-individual pharmacokinetic and pharmacodynamic variability is large. Constant monitoring of the CsA-concentration is therefore mandatory. 

    There are several analytical methods available for the determination of CsA, such as immunoassays, liquid chromatography (HPLC) and tandem mass spectrometry (LC-MS/MS). The department of Clinical Chemistry at the Central Hospital in Karlstad has for many years used a radioimmunoassay, the CYCLO-Trac SP® from DiaSorin, for CsA-determinations. The laboratory wants to replace this method, which uses radioactive isotopes, with a faster and more selective LC-MS/MS method. 

    In this work a LC-MS/MS method, utilizing positive electrospray, with a fast sample preparation and chromatography for the determination of CsA in whole blood has been developed and validated. Two protein precipitation procedures were evaluated for sample preparation during the method development and two different internal standards were tested; the CsA analog cyclosporine D (CsD) and an isotope labelled CsA (d12-CsA). The LC-MS/MS assay was fully validated and implemented in the routine work at the laboratory on November 1 2009. Results from both the CYCLO-Trac SP® method and the LC-MS/MS assay will be reported for at least five months.

  • 37.
    Lesko, Marek
    et al.
    Rzeszów University of Technology, Poland.
    Åsberg, Dennis
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Enmark, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Kaczmarski, Krzysztof
    Poland.
    Choice of Model for Estimation of Adsorption Isotherm Parameters in Gradient Elution Preparative Liquid Chromatography2015In: Chromatographia, ISSN 0009-5893, E-ISSN 1612-1112, Vol. 78, no 19-20, p. 1293-1297Article in journal (Refereed)
    Abstract [en]

    The inverse method is a numerical method for fast estimation of adsorption isotherm parameters directly from a few overloaded elution profiles and it was recently extended to adsorption isotherm acquisition in gradient elution conditions. However, the inverse method in gradient elution is cumbersome due to the complex adsorption isotherm models found in gradient elution. In this case, physicochemically correct adsorption models have very long calculation times. The aim of this study is to investigate the possibility of using a less complex adsorption isotherm model, with fewer adjustable parameters, but with preserved/acceptable predictive abilities. We found that equal or better agreement between experimental and predicted elution profiles could be achieved with less complex models. By being able to select a model with fewer adjustable parameters, the calculation times can be reduced by at least a factor of 10. 

  • 38.
    Lin, G.
    et al.
    Zhejiang Univ, China.
    Zhang, Y.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Örebro universitet.
    Cheng, X.
    Zhejiang Univ, China.
    Gulliksson, M.
    Örebro universitet.
    Forssén, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    A regularizing Kohn-Vogelius formulation for the model-free adsorption isotherm estimation problem in chromatography2018In: Applicable Analysis, ISSN 0003-6811, E-ISSN 1563-504X, Vol. 97, no 1, p. 13-40Article in journal (Refereed)
    Abstract [en]

    Competitive adsorption isotherms must be estimated in order to simulate and optimize modern continuous modes of chromatography in situations where experimental trial-and-error approaches are too complex and expensive. The inverse method is a numeric approach for the fast estimation of adsorption isotherms directly from overloaded elution profiles. However, this identification process is usually ill-posed. Moreover, traditional model-based inverse methods are restricted by the need to choose an appropriate adsorption isotherm model prior to estimate, which might be very hard for complicated adsorption behavior. In this study, we develop a Kohn-Vogelius formulation for the model-free adsorption isotherm estimation problem. The solvability and convergence for the proposed inverse method are studied. In particular, using a problem-adapted adjoint, we obtain a convergence rate under substantially weaker and more realistic conditions than are required by the general theory. Based on the adjoint technique, a numerical algorithm for solving the proposed optimization problem is developed. Numerical tests for both synthetic and real-world problems are given to show the efficiency of the proposed regularization method.

  • 39.
    Lipponen, Katriina
    et al.
    Univ Helsinki, Dept Chem, Analyt Chem Lab, FIN-00014 Helsinki, Finland..
    Stege, Patricia W.
    Univ Helsinki, Dept Chem, Analyt Chem Lab, FIN-00014 Helsinki, Finland.;Natl Univ San Luis, CONICET, Dept Chem, INQUISAL,Lab Analyt Chem, San Luis, Argentina..
    Cilpa, Geraldine
    Univ Helsinki, Dept Chem, Analyt Chem Lab, FIN-00014 Helsinki, Finland..
    Samuelsson, Jorgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Karlstad Univ, Dept Chem & Biomed Sci, SE-65188 Karlstad, Sweden.;Uppsala Univ, Dept Phys & Analyt Chem, SE-75124 Uppsala, Sweden..
    Riekkola, Marja-Liisa
    Univ Helsinki, Dept Chem, Analyt Chem Lab, FIN-00014 Helsinki, Finland..
    Three Different Approaches for the Clarification of the Interactions between Lipoproteins and Chondroitin-6-sulfate2011In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 83, no 15, p. 6040-6046Article in journal (Refereed)
    Abstract [en]

    Two different experimental approaches were used for obtaining a comprehensive view and understanding of the interactions between apolipoprotein B-100 (ApoB-100) of low-density lipoprotein and apolipoprotein E (ApoE) of high-density lipoprotein and chondroitin-6-sulfate (C6S) of arterial proteoglycan. The techniques employed were partial filling affinity capillary electrophoresis (PF-ACE) and continuous flow quartz crystal inicrobalance (QCM). In addition, molecular dynamic (MD) simulations were used to provide a supportive visual insight into the interaction mechanism. A new tool for analysis of QCM-data was utilized, i.e., adsorption energy distribution calculations, which allowed a deeper understanding of the interactions, especially at different temperatures. The PF-ACE technique probed mainly the strong adsorption interactions whereas in the MD calculations short:- and long-range interactions could be distinguished. Although there are differences in the techniques, a pretty good agreement was achieved between the three approaches for the interaction of 19 amino acid peptide of ApoB with C6S giving log affinity constants of 4.66 by QCM, 5.02 by PP-ACE, and 7.39 by MD, and for 15 amino acid peptide of ApoE with C6S 5.34 by QCM, 5.28 by PT-ACE, and 4.60 by MD at physiological temperature 37.0 degrees C.

  • 40.
    Nguyen, Dinh Quynh Phu
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    The use of gas chromatography and high-performance liquid chromatography for the determination of biological components in plant materials2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Gas chromatography (GC) was used to determine biological components in commercial essential oils from leaves of Melaleuca cajuputi collected in the Thua Thien Hue province of Vietnam. The results show that the major components of cajuput oil were α-pinene, β-pinene, limonene, 1,8-cineole and terpineol, with 1,8‑cineol being present in the largest amounts, from 15 to 59 %. High-performance liquid chromatography (HPLC) was used to determine benzoic acid and sorbic acid preservative concentrations in different foodstuffs. The results demonstrate that the concentrations were below the maximum levels allowed by European Commission regulations in all samples.

  • 41.
    Olsson, Jeanette
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    New Techniques for Chiral Separations2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Gas chromatography (GC) has been utilized for the study of enantiomer resolution of the atropisomers of PCBs, o,p´-DDD and o,p´-DDT. Different substituents and concentrations of cyclodextrin, capillary dimensions and type of stationary phase films have been investigated to achieve the resolution of as many of the atropisomers on one column as possible. The results indicated that the butyl substitution of 6-hydroxyl and the methyl substitution of 2- and 3-hydroxyl were the most promising for the enantiomeric separation. Using Capillary Electrophoresis (CE), the trimers and monomers of PM-β-CDs were compared for enantiomeric resolution, as well as comparing the cationic PMMA-β-CD with the anionic HS-β-CD. In these studies the trimer did not show an improved resolution for mepivacaine, when compared to the equimolar concentration of the monomer. The cationic CD gave increased resolution values for ibuprofen when compared to the anionic CD. A scheme for reversing enantiomeric elution order of both the basic propranolol and acidic ibuprofen is also presented, with the aim of facilitating the detection of impurities in a high sample loading. The detection of 1% of each enantiomer of propranolol, and 1% of R(-)-ibuprofen, was demonstrated, with elution prior to the tailing peak of the corresponding enantiomer. Dimethylacrylamide-coated capillaries were used in this work, and the stability of this coating was demonstrated, giving a highly reduced electroosmotic flow for up to six months. Enantiomeric baseline separations of omeprazole and 5-hydroxyomeprazole have also been achieved with both CE and Open Tubular Capillary Electrochromatography (OT-CEC) methods. With CE-UV, both a non-aqueous method (using HDMS-β-CD) and an aqueous method (using HS-β-CD) were used for enantiomeric resolution of the two racemates. Resolution of omeprazole was also achieved using CE-Electrospray Ionization-Mass Spectrometry (ESI-MS). In OT-CEC, avidin was immobilized on the inside surface of a fused silica capillary and was employed as chiral selector for the enantiomeric baseline resolution of omeprazole and 5-hydroxyomeprazole.

  • 42.
    Olsson, Jeanette
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Blomberg, Lars G.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Enantioseparation of Omeprazole and its Metabolite 5-Hydroxyomeprazole using Open Tubular Capillary Electrochromatography with Immobilized Avidin as Chiral Selector2008In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 875, no 1, p. 329-332Article in journal (Refereed)
    Abstract [en]

    The present paper demonstrates the enantiomeric separation of omeprazole and its metabolite 5-hydroxyomeprazole performed with open tubular capillary electrochromatography (OT-CEC). The protein avidin was used as the chiral selector. Avidin was immobilized by a Schiffs base type of reaction where the protein was via glutaraldehyde covalently bonded to the amino-modified wall of a fused-silica capillary, 50 μm i.d. Both racemates were baseline resolved. Resolution was 1.9 and 2.3, respectively, using ammonium acetate buffer, pH 5.8, 5% methanol, with UV-detection. These values of resolution using OT-CEC are higher than earlier published results regarding chiral separation of omeprazole and 5-hydroxyomeprazole on packed CEC. The number of theoretical plates also indicated good separation efficiency.

  • 43.
    Olsson, Ola
    Karlstad University, Faculty of Technology and Science.
    Affinity capillary electrophoresis of Beta-2-glycoprotein I and Anionic phospholipids2010Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
  • 44.
    Petersson, Patrik
    et al.
    AstraZeneca R&D Lund, SE-221 87 Lund, Sweden.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Edström, Lena
    Department of Physical and Analytical Chemistry, BMC Box 577, SE-751 23 Uppsala, Sweden.
    Samie, Farzad
    AstraZeneca Nordic Headquarters (ISMO), Södertälje.
    Tatterton, Stephen
    AstraZeneca R&D Charnwood, Loughborough, Leicestershire LE11 5RH, UK.
    Clarke, Adrian
    AstraZeneca R&D Charnwood, Loughborough, Leicestershire LE11 5RH, UK.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Why ultra high performance liquid chromatography produces more tailing peaks than high performance liquid chromatography, why it does not matter and how it can be addressed2011In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 1218, no 39, p. 6914-6921Article in journal (Refereed)
    Abstract [en]

    The purpose of this study is to demonstrate, with experiments and with computer simulations based on a firm chromatographic theory, that the wide spread perception of that the United States Pharmacopeia tailing factor must be lower than 2 (Tf &lt; 2) is questionable when using the latest generation of LC equipment. It is shown that highly efficient LC separations like those obtained with sub-2 μm porous and 2.7 μm superficially porous particles (UHPLC) produce significantly higher Tf-values than the corresponding separation based on 3 μm porous particles (HPLC) when the same amount of sample is injected. Still UHPLC separations provide a better resolution to adjacent peaks. Expressions have been derived that describe how the Tf-value changes with particle size or number of theoretical plates. Expressions have also been derived that can be used to scale the injection volume based on particle size or number of theoretical plates to maintain the Tf-value when translating a HPLC separation to the corresponding UHPLC separation. An aspect that has been ignored in previous publications. Finally, data obtained from columns with different age/condition indicate that Tf-values should be complemented by a peak width measure to provide a more objective quality measure.

  • 45.
    Pimrote, Wachirawan
    et al.
    Naresuan University, Phayao Campus, Thailand.
    Ratana-Ohpas, Roongroje
    Walailak University, Thailand.
    Renman, Lars
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    A Combination Bismuth Bulk Electrode and Its Use in Adsorptive Constant-Current Stripping Chronopotentiometry for Iron Using Solochrome Violet RS2011In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 23, no 7, p. 1607-1614Article in journal (Refereed)
    Abstract [en]

    A new combination bismuth bulk electrode allowing potentiostatic control to be maintained in a suspended sample drop is described. The electrode was tested by adsorptive constant-current stripping chronopotentiometry for iron-(III) using Solochrome Violet RS.

  • 46.
    Pruim, Peter
    et al.
    Univ Amsterdam, Analyt Chem Grp, Vant Hoff Inst Mol Sci, NL-1090 GD Amsterdam, Netherlands..
    Ohman, Marcus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Schoenmakers, Peter J.
    Univ Amsterdam, Analyt Chem Grp, Vant Hoff Inst Mol Sci, NL-1090 GD Amsterdam, Netherlands..
    Kok, Wim Th.
    Univ Amsterdam, Analyt Chem Grp, Vant Hoff Inst Mol Sci, NL-1090 GD Amsterdam, Netherlands..
    Methacrylate monolithic stationary phases for gradient elution separations in microfluidic devices2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 31, p. 5292-5297Article in journal (Refereed)
    Abstract [en]

    Methacrylate monolithic stationary phases were produced in fused-silica chips by UV initiation. Poly(butyl methacrylate-co-ethylene dimethacrylate) (BMA) and poly(lauryl methacrylate-co-ethylene dimethacrylate) (LMA) monoliths containing 30, 35 and 40% monomers were evaluated for the separation of peptides under gradient conditions. The peak capacity was used as an objective tool for the evaluation of the separation performance. LMA monoliths of the highest density gave the highest peak capacities (approximate to 40) in gradients of 15 min and all LMA monoliths gave higher peak capacities than the BMA monoliths with the same percentage of monomers. Increasing the gradient duration to 30 min did not increase the peak capacity significantly. However, running fast (5 min) gradients provides moderate peak capacities (approximate to 20) in a short time. Due to the system dead volume of 1 mu L and the low bed volume of the chip, early eluting peptides migrated over a significant part of the column during the dwell time under isocratic conditions. It was shown that this could explain an increased band broadening on the monolithic stationary phase materials used. The effect is stronger with BMA monoliths, which partly explains the inferior performance of this material with respect to peak capacity. The configuration of the connections on the chip appeared to be critical when fast analyses were performed at pressures above 20 bar. (C) 2011 Elsevier B.V. All rights reserved.

  • 47.
    Samuelsson, Jörgen
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Eiriksson, F. F.
    University of Iceland.
    Åsberg, Dennis
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Thorsteinsdóttir, M.
    University of Iceland.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Determining gradient conditions for peptide purification in RPLC with machine-learning-based retention time predictions2019In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1598, p. 92-100Article in journal (Refereed)
    Abstract [en]

    A strategy for determining a suitable solvent gradient in silico in preparative peptide separations is presented. The strategy utilizes a machine-learning–based method, called ELUDE, for peptide retention time predictions based on the amino acid sequences of the peptides. A suitable gradient is calculated according to linear solvent strength theory by predicting the retention times of the peptides being purified at three different gradient slopes. The advantage of this strategy is that fewer experiments are needed to develop a purification method, making it useful for labs conducting many separations but with limited resources for method development. The preparative separation of met-enkephalin and leu-enkephalin was used as model solutes on two stationary phases: XBridge C18 and CSH C18. The ELUDE algorithm contains a support vector regression and is pre-trained, meaning that only 10–50 peptides are needed to calibrate a model for a certain stationary phase and gradient. The calibration is done once and the model can then be used for new peptides similar in size to those in the calibration set. We found that the accuracy of the retention time predictions is good enough to usefully estimate a suitable gradient and that it was possible to compare the selectivity on different stationary phases in silico. The absolute relative errors in retention time for the predicted gradients were 4.2% and 3.7% for met-enkephalin and leu-enkephalin, respectively, on the XBridge C18 column and 2.0% and 2.8% on the CSH C18 column. The predicted retention times were also used as initial values for adsorption isotherm parameter determination, facilitating the numerical calculation of overloaded elution profiles. Changing the trifluoroacetic acid (TFA) concentration from 0.05% to 0.15% in the eluent did not seriously affect the error in the retention time predictions for the XBridge C18 column, an increase of 1.0 min (in retention factor, 1.3). For the CSH C18 column the error was, on average, 2.6 times larger. This indicates that the model needs to be recalibrated when changing the TFA concentration for the CSH column. Studying possible scale-up complications from UHPLC to HPLC such as pressure, viscous heating (i.e., temperature gradients), and stationary-phase properties (e.g., packing heterogeneity and surface chemistry) revealed that all these factors were minor to negligible. The pressure effect had the largest effect on the retention, but increased retention by only 3%. In the presented case, method development can therefore proceed using UHPLC and then be robustly transferred to HPLC.

  • 48.
    Samuelsson, Jörgen
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Enmark, Martin
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Highlighting Important Parameters Often Neglected in Numerical Optimization of Preparative Chromatography2012In: Chemical Engineering & Technology, ISSN 0930-7516, E-ISSN 1521-4125, Vol. 35, no 1, p. 149-156Article in journal (Refereed)
    Abstract [en]

    When a chromatographic separation process is numerically optimized, a number of input parameters to the column model need to be accurately determined, and the accuracy will affect the reliability of the predicted optimal operational conditions. Furthermore, the numerical accuracy of the solution to the column model will have similar impact. The input parameters holdup volume, injection profiles, and the selection of an algorithm for solving the column model were investigated. Errors in parameters or a numerical error in the solution of the column model were found to lead to a prediction of a product fraction where the set purity and/or yield requirements are not met.

  • 49.
    Samuelsson, Jörgen
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Enmark, Martin
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Högblom, Joakim
    Eka Chemicals.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Characterization of adsorption in SFC: An evaluation of methods used in LC2012Conference paper (Refereed)
    Abstract [en]

    Recently the pharmaceutical industry has started to replace HPLC with SFC because of incentives to lower the environmental impact and as well as increasing performance. Reliable characterization of the adsorption processes in SFC, is therefore of utmost importance. The key thermodynamic phase system information is obtained by rigorous determination of adsorption isotherms over a broad concentration range. If properly processed, this data gives not only correct information about the degree of heterogeneity but also the values of the energy of interactions and monolayer capacities of each individual type of adsorption site in the phase system; ultimately, this can result in identification of the types of interactions (dipole-dipole, van der Waals interactions etc.). In this study, we will present the transfer of LC adsorption characterization methods to SFC conditions using several model compounds with several different methods for adsorption isotherm determination traditionally applied with success in LC, and now modified for SFC. We have limited our investigation to methanol as modifier and used the operational conditions, temperature and backpressure most typically observed in industrial settings; in addition, we have used commercial standard SFC-equipment. The results clearly shows that adsorption isotherm determinations in SFC are considerably more complicated than in LC; we will go through the most important pitfalls and give guidelines for more rigorous determinations of adsorption data in SFC. This is an industrial – academic cooperation in the Fundamental Separation Science Group www.separationscience.se

  • 50.
    Samuelsson, Jörgen
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Högblom, Joakim
    Eka Chemicals.
    A Holistic View on Optimization of Preparative Liquid Chromatography – Importance of Column Properties and Design.2012Conference paper (Refereed)
    Abstract [en]

    Several important studies based on firm theory ground - have been made on the different parameters of importance in chromatographic process optimizations during the recent years. In this presentation we take an holistic view by investigating i) the relative importance of the operational parameters and column properties and ii) how these effect the optimal column design. For optimization we used an advanced global response surface method combined with local gradient methods. As a model system we used the practical problem of purification of one or both optical isomers of a racemate. In the first part, we investigated the relative importance of stationary phase characteristics such as: (i) the retention factor, (ii) the selectivity, (iii) the saturation capacity (iv), the efficiency and (v) the maximum allowed operational pressure. In the second part we investigated how the optimal column design for a preparative separation problem is affected by column properties, such as particle size, and optimization constraints, such as required yield. The investigation showed – in contrast to what is generally believed – that the saturation capacity of the stationary phase is of minor importance, instead the maximum allowed operational pressure is one of the most important parameter. Moreover, smaller size packing materials always shows much lower solvent consumption. This is a great environmental and economical advantage of using smaller packing materials. Rules of thumbs, derived from the holistic optimizations, will be given for industrial preparative settings in the batch mode.

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