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  • 151.
    Delbro, Dick
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Lång, P
    Lange, S
    Andersson, G
    Induction and cellular expression of tartrate resistant acid phosphatase during dextran sodium sulphate induced colitis in rats2009In: Histochemistry and Cell Biology, ISSN 0948-6143, E-ISSN 1432-119X, Vol. 132, no 6, p. 599-612Article in journal (Refereed)
    Abstract

    The aim of this study was to investigate the

    cellular and molecular expression of tartrate resistant acid phosphatase (TRAP) as a marker of activated macrophages in macrophage dependent dextran sulphate sodium (DSS)-induced colitis in rats. In normal colon, TRAP+/CX3CR1+ macrophages were located in the upper part of the lamina propria. In the early stage (day 13) of acute colitis prior to

    histopathological changes, induction of the cytokines

    TNF, IL-12 and IFNgamma occurred concomitant with

    increased mRNA and enzyme activity of TRAP along with

    a slight increase of TRAP immunolabelling in macrophages of the upper lamina propria, suggesting induction of TRAP in resident macrophages. Among these cytokines,TNFalpha up-regulated TRAP expression in the RAW 264.7 monocyte/macrophage cell line. In a later phase (day 7) with fulminant colitis, a massive infiltration of macrophages including recruited TRAP+/CCR2+ cells was observed also in the lower part of the lamina propria as well as in the submuscular layer. Additionally, diVerentiated cellular

    expression of pro- and mature TRAP also suggest that

    mucosal macrophages in the lower part of lamina propria

    bordering the sub-mucosa provide a source of replenishment of macrophages situated in the upper lamina propria.

    In conclusion, induction of TRAP provides an early sign of macrophage responsiveness in DSS induced colitis

  • 152.
    Delbro, Dick
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Novotny, Ann
    Edsparr, Karin
    Nylund, Gunnar
    Khorram-Manesh, Amir
    Albertsson, Per
    Nordgren, Svante
    A pharmacological analysis of the cholinergic regulation of urokinase-type plasminogen activator secretion in the human colon cancer cell line, HT-292010In: European Journal of Pharmacology, ISSN 0014-2999, Vol. 646, no 1,2,3, p. 22-30Article in journal (Refereed)
    Abstract [en]

    Urokinase-type plasminogen activator (uPA) is an important factor for tumour cell invasion and metastasis. We recently showed that acetylcholine is an autocrine/paracrine growth factor for the human colon cancer cell line, HT-29, in part via the 7 subtype of the nicotinic acetylcholine receptors. In the current study, we investigated whether acetylcholine participates in the regulation of the protein expressions of also uPA and its receptor (uPAR) in the HT-29 cell line. Such were investigated by immunocytochemistry and Western blotting, and quantitation of uPA secretion was undertaken by ELISA. Stimulation of the cells for 24h with nicotine caused increased uPA secretion with peak effect (78% above the control) occurring at a nicotine concentration of 10nM. This effect was markedly inhibited by -Bungarotoxin, thus showing the involvement of 7 nicotinic acetylcholine receptors. Basal uPA secretion was found to be partly dependent on ongoing activation of nicotinic receptors, suggesting tonic production of acetylcholine. Conversely, there was no cholinergic influence on the expression of uPAR. The current findings demonstrate novel aspects of receptor-mediated regulation of tumour metastatic potential via uPA secretion. This may suggest future pharmaceutical strategies in treatment of colorectal cancer.

  • 153.
    Delbro, Dick
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Pettersson, A
    Nilsson, L
    Nylund, G
    Khorram-Manesh, A
    Nordgren, S
    Is acetylcholine an autocrine/paracrine growth factor via the nicotinic α-receptor subtype in the human colon cancer cell line HT-29?2009In: European Journal of Pharmacology, ISSN 0014-2999, E-ISSN 1879-0712, Vol. 609, no 1-3, p. 27-33Article in journal (Refereed)
    Abstract

    We used immunochemistry to demonstrate expression of acetylcholine's nicotinic 7-receptor subtype in

    human colon cancer cell line HT-29. Moreover, RT-PCR and immunochemistry showed that choline

    acetyltransferase and acetylcholine esterase, the enzymes responsible for acetylcholine synthesis and

    degradation, respectively, localise in HT-29 cells. Bromoacetylcholine bromide, an inhibitor of choline

    acetyltransferase, significantly attenuated basal cell growth. Our findings suggest that acetylcholine might

    serve as an autocrine/paracrineor speculatively, even intracrinesignalling molecule in cell line HT-29, thus

    contributing to carcinogenesis/cancer progression

  • 154.
    Delbro, Dick
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Pettersson, A
    Nylund, G
    Khorram-Manesh, A
    Nordgren, S
    Nicotine induced modulation of SLURP-1 expression in human colon cancer cells2009In: Autonomic Neuroscience, ISSN 1566-0702, Vol. 148, no 1-2, p. 97-100Article in journal (Refereed)
    Abstract [en]

    The secreted mammalian Ly-6urokinase plasminogen activator receptor-related protein-1 (SLURP-1) is anendogenous ligand at the 7 subunit of the nicotinic acetylcholine receptor (nAChR). SLURP-1 has antitumourigenic properties. In the current study, we demonstrate that the challenge of HT-29 human coloncancer cells with nicotine for 24 h to increase cell growth via the 7nAChRs, caused a marked reduction ofthe protein expression of SLURP-1. We suggest that there is an interplay between acetylcholine and SLURP-1in the HT-29 cells, both molecules serving as autocrine growth controlling ligands at the 7nAChR, where acetylcholine regulates the release of SLURP-1

  • 155.
    Delbro, Dick S.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Expression of the non-neuronal cholinergic system in rat beta-cells2012In: Autonomic Neuroscience: Basic & Clinical, ISSN 1566-0702, E-ISSN 1872-7484, Vol. 167, no 1-2, p. 75-77Article in journal (Refereed)
    Abstract [en]

    Various markers of the cholinergic system (like e.g. choline acetyltransferase) were demonstrated by immunohistochemistry in, seemingly, beta-cells of rat pancreas. The findings may suggest an autocrine role of acetylcholine for the beta-cells. (C) 2011 Elsevier B.V. All rights reserved.

  • 156. Draeger, A
    et al.
    Nathrath, WBJ
    Lane, EB
    Sundström, Birgitta
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Stigbrand, T
    Immunohistochemical localization of cytokeratins, smooth muscle actin and vimentin in human normal salivery glands and pleomorphic adenomas with particular reference to myoepithelial and basal cells1991In: APMIS 1991;99:405-415Article in journal (Refereed)
  • 157.
    Drechsler, Michal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Are Models used from a 'Nature of Science' Perspective?2010Conference paper (Refereed)
  • 158.
    Drechsler, Michal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Models in chemistry education: A study of teaching and learning acids and bases in Swedish upper secondary schools2007Doctoral thesis, monograph (Other academic)
  • 159.
    Drechsler, Michal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Relating course theory to school practice: a study of science student teachers learning2011Conference paper (Refereed)
  • 160.
    Drechsler, Michal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Teachers' perceptions of the teaching of acids and bases in Swedish upper secondary schools2008Conference paper (Refereed)
  • 161.
    Drechsler, Michal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Textbooks', Teachers', and Students' Understanding of Acid-Base Models2005Conference paper (Refereed)
  • 162.
    Drechsler, Michal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Textbooks', teachers', and students' understanding of models used to explain acid-base reactions2005Licentiate thesis, monograph (Other academic)
  • 163.
    Drechsler, Michal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Textbooks', teachers', and students' understanding of models used to explain acid-base reactions2004Conference paper (Other (popular science, discussion, etc.))
  • 164.
    Drechsler, Michal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    The teaching and learning of acids and bases in Swedish upper secondary school2008Conference paper (Refereed)
  • 165.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Bergqvist, Anna
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    de Jong, Onno
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    The case of chemical bonding models: Teachers' knowledge and textbooks' influences2010Conference paper (Refereed)
  • 166.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Henriksson, D.
    Wiberg, K.
    Computerised automatisation of magnesium and calcium analysis in water using a highly sensitive cheap mini-spectrometer based on high intensive LED's1999Conference paper (Other (popular science, discussion, etc.))
  • 167.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Schmidt, Hans-Jürgen
    Textbooks' and teachers' understanding of acid-base models used in chemistry teaching2005In: Chemistry Education: Research and Practice, 2005, 6(1), 19-35Article in journal (Refereed)
  • 168.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Schmidt, Hans-Jürgen
    Textbooks’ and teachers’ understanding of acid-base models used in chemistry teaching2005In: Chemistry education, ISSN 1109-4028, E-ISSN 1109-4028, Vol. 6, no 1, p. 19-39Article in journal (Refereed)
  • 169.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Schmidt, H.-J.
    Schoolbooks´ and teachers´ awareness of chemists´ acid-base theories2003Conference paper (Other (popular science, discussion, etc.))
  • 170.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Schmidt, H.-J.
    Schoolbooks' and teachers' awareness of different acid-base models used in chemistry teaching2004Conference paper (Refereed)
  • 171.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Schmidt, H.-J.
    Två skandinaviska forskares syn på syror och baser. Vem tror eleverna på?2004Conference paper (Other (popular science, discussion, etc.))
  • 172.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Schmidt, H.-J.
    Upper Secondary School Students' Understanding of Models Used in Chemistry to Define Acids and Bases2005In: Science Education International. 16 (1), (2005) 39-54Article in journal (Refereed)
  • 173.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Van Driel, J. H.
    Experienced Swedish science teachers' Pedagogical Content Knowledge of teaching acids-base chemistry2007Conference paper (Refereed)
  • 174.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Van Driel, J. H.
    Experienced Teachers' pedagogical content knowledge of teaching acid-base chemistry2006Conference paper (Refereed)
  • 175.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Van Driel, J. H.
    Experienced Teachers' pedagogical content knowledge of teaching acid-base chemistry2006Conference paper (Other academic)
  • 176.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Van Driel, J. H.
    Teaching acids and bases in Swedish upper secondary schools2008Conference paper (Refereed)
  • 177.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Van Driel, Jan
    ICLON, Leiden University, Graduate School of Teaching, The Netherlands.
    Experienced teachers' pedagogical content knowledge of teaching acid-base chemistry2008In: Research in science education, ISSN 0157-244X, E-ISSN 1573-1898, Vol. 38, no 5, p. 611-631Article in journal (Refereed)
    Abstract [en]

    We investigated the pedagogical content knowledge (PCK) of nine experienced chemistry teachers. The teachers took part in a teacher training course on students’ difficulties and the use of models in teaching acid–base chemistry, electrochemistry, and redox reactions. Two years after the course, the teachers were interviewed about their PCK of (1) students’ difficulties in understanding acid–base chemistry and (2) models of acids and bases in their teaching practice. In the interviews, the teachers were asked to comment on authentic student responses collected in a previous study that included student interviews about their understanding of acids and bases. Further, the teachers drew story-lines representing their level of satisfaction with their acid–base teaching. The results show that, although all teachers recognised some of the students’ difficulties as confusion between models, only a few chose to emphasise the different models of acids and bases. Most of the teachers thought it was sufficient to distinguish clearly between the phenomenological level and the particle level. The ways the teachers reflected on their teaching, in order to improve it, also differed. Some teachers reflected more on students’ difficulties; others were more concerned about their own performance. Implications for chemistry (teacher) education are discussed.

  • 178.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Van Driel, Jan
    ICLON, Leiden University, Graduate School of Teaching, The Netherlands.
    Teachers’ knowledge and beliefs about the teaching of acids and bases in Swedish upper secondary schoolsManuscript (preprint) (Other academic)
  • 179.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    van Driel, Jan
    Teachers perceptions of the teaching of acids and bases in Swedish upper secondary schools2009In: Chemistry education, ISSN 1109-4028, E-ISSN 1109-4028, Vol. 10, no 2, p. 86-96Article in journal (Refereed)
  • 180. Dugo, P.
    et al.
    Presti, M.Lo.
    Öhman, Marcus
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Fazio, A.
    Dugo, G.
    Mondello, L.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Determination of flavonoids in citrus juices by micro-HPLC-ESI-MS2005In: J. Sep. Sci., 28 (2005) 1149-1156Article in journal (Refereed)
  • 181.
    Edberg, Andreas
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    PCR detection and prevalence of Mycoplasma genitalium2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Chlamydia and gonorrhea are major causes of sexually transmitted infections (STI) in adolescents worldwide. The infections are caused by Chlamydia trachomatis or Neisseria gonorrhoeae, bacteria with clinical manifestations such as urethritis, prostatitis and epididymitis among men, and urethritis, cervicitis and upper genital tract infection (i.e. pelvic inflammatory disease) among women. However, in many cases of genital tract infection, the etiology remains uncertain. In light of this, Mycoplasma genitalium was somewhat accidentally isolated in 1980 after prolonged incubation of urogenital specimens from men with non-gonococcal urethritis. Following the initial isolation in 1980, repeated attempts have been made to recover the extremely fastidious organism from clinical samples by culture techniques, but isolates have been rare and difficult to obtain. With the development of PCR methods in the early 1990s, detection of M. genitalium infection became more feasible.

    The aim in paper I was to compare three different PCR assays (conventional and real-time 16S rRNA gene PCR as well as real-time Mycoplasma genitalium adhesin protein (MgPa) gene PCR) for detection of M. genitalium. The study also determined the prevalence of M. genitalium. Clinical specimens collected from STI attendees, 381 men and 298 women, were used to determine the prevalence of M. genitalium and 213 of these specimens were used in the PCR comparative study. The prevalence of M. genitalium infection in men and women was 27/381 (7.1 %) and 23/298 (7.7 %) respectively. In the PCR comparative study, M. genitalium DNA were detected in 61/76 (80.3 %) of true-positive specimen by conventional 16S rRNA gene PCR, in 52/76 (68.4 %) by real-time 16S rRNA gene PCR and in 74/76 (97.4 %) by real-time MgPa gene PCR. Hence, real-time MgPa gene PCR is well suited for clinical diagnosis of M. genitalium in urogenital specimens from men and women.

    The aim in paper II was to determine whether a patients’ endocervical swab specimen can be transported in first void urine (FVU) as combined specimens in detection of Mycoplasma genitalium by real-time PCR. The study also compared two different DNA extraction methods (manual Chelex DNA extraction and automated BioRobot M48 DNA extraction) for observation of possible PCR inhibition. Clinical specimens collected from 329 women attending a STI clinic were used in the study. A total of 100 endocervical swab specimens transported in FVU was used in the PCR inhibition analysis. M. genitalium was detected in 25/329 (7.6 %) women. Endocervical swab specimens transported in FVU demonstrate higher sensitivity compared to both FVU alone and specimens transported in 2-SP medium detecting 24/25 (96 %), 22/25 (88 %) and 17/25 (68 %) of M. genitalium positive women, respectively. Automated BioRobot M48 DNA extraction was shown to be superior to manual Chelex extraction leaving no PCR inhibition and slightly higher DNA yield and/or better sensitivity. The results from these two studies are important knowledge in establishing the future diagnostic level of this STI in our county and also nationally.

  • 182.
    Edberg, Andreas
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Aronsson, Fredrik
    Department of Clinical Microbiology, Central Hospital, Karlstad, Sweden .
    Johansson, Eva
    Department of Infectious Diseases, Central Hospital, Karlstad, Sweden.
    Wikander, Elisabeth
    Department of Clinical Microbiology, Central Hospital, Karlstad, Sweden .
    Ahlqvist, Thomas
    Department of Clinical Microbiology, Central Hospital, Karlstad, Sweden .
    Fredlund, Hans
    Department of Clinical Microbiology, University Hospital, Örebro, Sweden .
    Endocervical swabs transported in first void urine as combined specimens in the detection of Mycoplasma genitalium by real-time PCR2009In: Journal of Medical Microbiology, ISSN 0022-2615, E-ISSN 1473-5644, Vol. 58, p. 117-120Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to determine whether a patient’s endocervical swab specimen can be transported in first void urine (FVU) as combined specimens for the detection of Mycoplasma genitalium by real-time PCR. The study also compared two different DNA extraction methods for observation of possible PCR inhibition. Three specimens, one endocervical swab specimen transported in 2-SP medium, one endocervical swab specimen transported in FVU and a FVU specimen, were collected from 329 women. All sample types underwent manual DNA extraction whereas in the DNA extraction study, 329 endocervical swab specimens transported in FVU were subjected to both manual Chelex and automated BioRobot M48 DNA extraction. A total of 100 endocervical swab specimens transported in FVU from patients PCR-negative for M. genitalium in the study were used in the PCR inhibition analysis. M. genitalium was detected in 25/329 (7.6 %) women. The endocervical swab specimens transported in 2-SP medium and transported in FVU were positive for M. genitalium in 17/25 (68 %) and 24/25 (96 %) women, respectively. The FVU specimens alone were positive for M. genitalium in 22/25 (88 %) women. In the DNA extraction study, M. genitalium DNA was detected in 24/329 (7.3 %) and 28/329 (8.5 %) of endocervical swab specimens transported in FVU subjected to manual Chelex extraction and automated BioRobot M48 extraction, respectively. Partial PCR inhibition was detected in 6% of samples subjected to manual Chelex extraction whereas no inhibition was detected with the automated BioRobot M48 extraction. Thus endocervical swab specimens transported in FVU demonstrate higher sensitivity than FVU specimens only and have considerably increased sensitivity compared with endocervical swab specimens transported in 2-SP medium for detection of M. genitalium DNA. Moreover, automated BioRobot M48 extraction was shown to be superior to a crude manual Chelex extraction, leaving no PCR inhibition and giving a slightly higher DNA yield and/or better sensitivity.

  • 183.
    Edberg, Andreas
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Jurstrand, Margaretha
    Department of Clinical Microbiology, University Hospital, Örebro, Sweden .
    Johansson, Eva
    Department of Infectious Diseases, Central Hospital, Karlstad, Sweden .
    Wikander, Elisabeth
    Department of Clinical Microbiology, Central Hospital, Karlstad, Sweden .
    Höög, Anna
    Department of Clinical Microbiology, Central Hospital, Karlstad, Sweden .
    Ahlqvist, Thomas
    Department of Clinical Microbiology, Central Hospital, Karlstad, Sweden .
    Falk, Lars
    Department of Dermatology and Venereology, Linköping University Hospital, County of Östergötland, Linköping, Sweden .
    Skov Jensen, Jørgen
    Mycoplasma Laboratory, Statens Serum Institute, Copenhagen S, Denmark .
    Fredlund, Hans
    Department of Clinical Microbiology, University Hospital, Örebro, Sweden .
    A comparative study of three different PCR assays for detection of Mycoplasma genitalium in urogenital specimens from men and women2008In: Journal of Medical Microbiology, ISSN 0022-2615, E-ISSN 1473-5644, Vol. 57, no 3, p. 304-309Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to compare conventional 16S rRNA gene PCR, real-time 16S rRNA gene PCR and real-time Mycoplasma genitalium adhesin protein (Mg gene PCR as detection methods for M. genitalium infection. The study also determined the prevalence of M. genitalium in male and female patients attending a sexually transmitted infections clinic in a rural area in the west of Sweden. First void urine (FVU) and/or urethral swabs were collected from 381 men, and FVU and/or cervical swabs and/or urethral swabs were collected from 298 women. A total of 213 specimens were used in the PCR comparative study: 98 consecutively sampled specimens from patients enrolled in the prevalence study, 36 consecutively sampled specimens from patients with symptoms of urethritis and 79 specimens from patients positive for M. genitalium by real-time MgPa gene PCR in the prevalence study. A true-positive M.genitalium DNA specimen was defined as either a specimen positive in any two PCR assays or a specimen whose PCR product was verified by DNA sequencing. The prevalence of M. genitalium infection in men and women was 27/381 (7.1 %) and 23/298 (7.7 %), respectively. In the PCR comparative study, M. genitalium DNA was detected in 61/76 (80.3%) of true-positive speciemens of conventional 16S rRNA gene PCR, in 52/76 (68.4 %) by real-time 16S rRNA gene PCR and in 74/76 (97.4 %) by real-time MgPa gene PCR. Real-time MgPa gene PCR thus had higher sensitivity compared with conventional 16S rRNA gene PCR and had considerably increased sensitivity compared with real-time 16S rRNA gene PCR for detection of M. genitalium DNA. Real-time MgPa gene PCR is well suited for the clinical diagnosis of M. genitalium.

  • 184. El-Beqqali, Aziza
    et al.
    Kussak, Anders
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Abdel-Rehim, Mohamed
    Microextraction in packed syringe / liquid chromatography /electrospray tandem mass spectrometry for quantification of acebutolol and metoprolol in human plasma and urine samples2007In: J. Liq. Chromatogr. & Relat. Technol., 30 (2007) 575-586Article in journal (Refereed)
  • 185.
    Enmark, Martin
    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.
    Gyllenhaal, Olle
    Computer-assisted optimization in preparative SFC, Challenges, Pitfalls and Solutions2010Conference paper (Refereed)
    Abstract [en]

    Preparative packed column SFC (pSFC) is an environmentally favorable alternative to normal phase HPLC. We are participating in a larger research project where the overreaching goal is to make an impact in the recovery of high-value compounds from agricultural byproducts and waste materials using environmentally sustainable techniques. Our specific task is to isolate large amounts of valuable compounds from discarded biomaterials using pSFC. It is still not possible to accurately model, simulate and optimize a preparative SFC proess, although SFC has been in use for almost fifty years. This is mainly because of the compressibility of the mobile phase and how this influences the physical parameters of the system. More particular, if pSFC is operated under combinations of back pressures and flow rates that give negligible pressure drop, it has been demonstrated and implied, that the tools developed and used within HPLC, can be transferred and used successfully [1, 2]. However, when the pressure drop becomes noticeable, the induced density gradient significantly increases the complexity. An earlier study has clearly described the effect of this pressure gradient on the retention factor, and also the column efficiency [3]. However, it remains to be investigated how the entire adsorption isotherm depends on the density.In this study we will investigate the use of the inverse and the perturbation peak methods, originally developed within LC, to determine the nonlinear adsorption isotherm for i) negligible, and ii) non-negligible pressure drop conditions respectively. To do this, we will use a simple racemic substance and a cellulose based CSP with a column equipped with pressure sensors at the inlet and outlet. Using obtained parameters we will validate the methods by simulating the separation using a variable coefficient version of the Equilibrium-Dispersive model for cases i and ii. [1] S. Ottiger, J. Kluge, A. Rajendran , M. Mazzotti, J. Chromatogr., A 1162 (2007) 74-82[2] C. Wenda, A. Rajendran, J. Chromatogr., A 1216 (2009) 8750-8758[3]A. Rajendran, O. Kräuchi, M. Mazzotti, M. Morbidelli, J Chromatogr., A, 1092 (2005) 149-160[4] G. Guiochon, A. Felinger, D. G. Shirazi, A. M. Katti, Fundamentals of Preparative and Nonlinear Chromatography 2nd Ed, Elsevier Academic Press (2006).

  • 186.
    Enmark, Martin
    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.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Arnell, Robert
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Kaczmarski, Krzysztof
    A systematic investigation of algorithm impact in preparative chromatography with experimental verifications2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 5, p. 662-672Article in journal (Refereed)
    Abstract [en]

    Computer-assisted optimization of chromatographic separations requires finding the numerical solution of the Equilibrium-Dispersive (ED) mass balance equation. Furthermore, the competitive adsorption isotherms needed for optimization are often estimated numerically using the inverse method that also solves the ED equations. This means that the accuracy of the estimated adsorption isotherm parameters explicitly depends on the numerical accuracy of the algorithm that is used to solve the ED equations. The fast and commonly used algorithm for this purpose, the Rouchon Finite Difference (RFD) algorithm, has often been reported not to be able to accurately solve the ED equations for all practical preparative experimental conditions, but its limitations has never been completely and systematically investigated. In this study, we thoroughly investigate three different algorithms used to solve the ED equations: the RFD algorithm, the Orthogonal Collocation on Finite Elements (OCFE) method and a Central Difference Method (CDM) algorithm, both for increased theoretical understanding and for real cases of industrial interest. We identified discrepancies between the conventional RFD algorithm and the more accurate OCFE and CDM algorithms for several conditions, such as low efficiency, increasing number of simulated components and components present at different concentrations. Given high enough efficiency, we experimentally demonstrate good prediction of experimental data of a quaternary separation problem using either algorithm, but better prediction using OCFE/CDM for a binary low efficiency separation problem or separations when the compounds have different efficiency. Our conclusion is to use the RFD algorithm with caution when such conditions are present and that the rule of thumb that the number of theoretical plates should be greater than 1000 for application of the RFD algorithm is underestimated in many cases

  • 187.
    Enmark, Martin
    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.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Arnell, Robert
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Kaczmarski, Krzysztof
    Computer Assisted Optimization of Pharmaceutical Purification - The Impact of Algorithms and Experimental Approach2010Conference paper (Refereed)
    Abstract [en]

    Computer assisted process optimization of chromatographic separations requires the selection of computer algorithms and measurement of relevant parameters. In this study, we will investigate how the choice of algorithms and the number of performed initial experiments affect the estimated optimal separations conditions. We will focus on conditions typically encountered for slurry packing coated 20 µm CSP in large-scale columns used for pharmaceutical intermediate purification.Probably the most essential for parameters in this context are the adsorption isotherm parameters for the components. The rapid "inverse method" is commonly used and this method requires that one numerically solve the mass balance equations describing the chromatographic process. Here we thoroughly investigate how different algorithms that solve the Equilibrium-Dispersive (ED) mass balance equations will affect the estimated adsorption isotherm parameters.Furthermore, we will investigate and compare how different strategies affect the prediction of the optimal separation conditions. First, we will use a more rapid approach that requires a minimum of experiments and uses standard algorithms to estimate optimal conditions. Secondly, we will use a more exact approach that requires more experiments and uses more advanced simulation- and optimization algorithms

  • 188.
    Enmark, Martin
    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.
    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.
    Kaczmarski, Krzysztof
    A systematic investigation on the accuracy of computer simulations for optical isomers in industrial settings2010Conference paper (Refereed)
    Abstract [en]

    Predicting the band profiles of typical chromatographic separations using the approach of the inverse method (IM) [2] requires finding the numerical solution of the Equilibrium-Dispersive (ED) mass balance equation [1]. The accuracy of the determination of the competitive adsorption isotherms is therefore explicitly dependent on the choice of algorithm to solve the ED model. Earlier studies have shown that the well known RFD algorithm [3] has limitations in its accuracy for certain simulated conditions such as column efficiency and adsorption isotherm type [5]. In this study, we thoroughly investigate three different algorithms, the rapid and well known Rouchon Finite Difference (RFD) algorithm [3], the Orthogonal Collocation on Finite Elements (OCFE) method [4] and the Central Difference Method (CDM) algorithm developed by us. Firstly, a systematic investigation is made, comparing the different algorithms under a broad range of different synthetic conditions. Secondly, we apply all three algorithms using the IM on real experimental systems; (I) one high efficiency quaternary separation and (II) one pharmaceutical industry application with a chiral intermediate separation. We have found discrepancies between the conventional (RFD) and the more accurate (OCFE and CDM) algorithms for several synthetic conditions such as low efficiency, increasing number of simulated components and components present at different concentrations. Given high enough efficiency, we experimentally demonstrate good prediction of experimental data of a quaternary separation problem using either algorithm but better prediction of OCFE/CDM for a binary low efficiency separation problem. Our conclusion is to use the RFD algorithm with caution when any of the particular conditions we have investigated is valid. When the highest accuracy is sought, there is no doubt that OCFE or CDM should be the algorithms of choice. However, given the computational speed of RFD, we also recommend it for preliminary parameter fitting. For conditions where we have shown the algorithms to produce practically identical solutions, RFD can be applied with greater certainty. It remains to be thoroughly investigated the effect on the particular shape of the adsorption isotherm on the obtained solution, for example type III having inflection points.

  • 189.
    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 Deeper Understanding of a Complex Adsorption Behavior in a Common Chiral, Separation System2011Conference paper (Refereed)
    Abstract [en]

    The adsorption equilibria of racemic methyl mandelate on a tris-(3,5-dimethylphenyl)carbamoyl cellulose chiral stationary phase (CSP) was investigated. This separation has previously been performed and analyzed on a methylcellulose tribenzoate coated CSP. In that case, both enantiomers could be described with a bi-Langmuir adsorption isotherm, convex upwards (type I). In our case, two fundamentally different properties were observed. First, the elution order was reversed. Furthermore, only the less retained enantiomer shows 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 calculations. The less retained enantiomer was best described by Tóth adsorption isotherm while the second enantiomer was best described with a bi-Moreau adsorption isotherm. The Moreau model is an extension of the Langmuir model including non-ideal adsorbate-adsorbate interactions; here the unusual model provided 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 by synthetically generated raw adsorption slope data. It was demonstrated 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 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.

  • 190.
    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

  • 191.
    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.
    Characterization of the Adsorption of Racemic Methyl Mandelate on Tris-(3,5-dimethylphenyl)carbamoyl Cellulose Chiral Stationary Phase2011Conference paper (Refereed)
    Abstract

    The adsorption equilibria of racemic methyl mandelate on a tris-(3,5-dimethylphenyl)carbamoyl cellulose chiral stationary phase (CSP) was investigated. This separation has previously been performed and analyzed on a methylcellulose tribenzoate coated CSP. In that case, both enantiomers could be described with a bi-Langmuir adsorption isotherm, convex upwards (type I). In our case, two fundamentally different properties were observed. First, the elution order was reversed. Furthermore, only the less retained enantiomer shows 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 calculations. The less retained enantiomer was best described by Tóth adsorption isotherm while the second enantiomer was best described with a bi-Moreau adsorption isotherm. The Moreau model is an extension of the Langmuir model including non-ideal adsorbate-adsorbate interactions; here the unusual model provided 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 by synthetically generated raw adsorption slope data. It was demonstrated 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 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.

  • 192.
    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

  • 193.
    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.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Preparative Separation of Chiral Pharmaceutical Compounds - The Effects of Packing Particle Size, Pressure Limit and Column Geometry on Productivity and Solvent Consumption2011Conference paper (Refereed)
    Abstract [en]

    In this study, omeprazole was used as a model compound. Omeprazole and other related sulfoxidebenzimidazolesare used against gastric ulcersand have been extensively studied regarding chromatographic resolution techniques using several different chiral stationary phases.First, AstraZeneca launched Losec, a racemic mixture of RS-omeprazole. Facing loss of patent, the more potent S-enantiomer was developed and marketed as Nexium. Now the patent of Nexium is close expiration why methods for isolation of the pure S-enantiomer will be of importance for the generic pharmaceutical companies.The experimental model separation system represents a system with good selectivity and high solubility of the solute in the eluent. In this investigation the productivity optima for three different particle sizes (5, 10 and 25 µm) at maximum system pressure ranging from 50 to 400 bars are studied. Two different optimizations cases were studied in depth. First,a process optimization with fixed column geometry is studied. The results clearly show that larger packing materials have higher productivity at low pressure drops on the analytical size column.With increasing allowed pressure drops, over 200 bar, the smaller packing materials have substantially higher productivity. The results also show that smaller packing material will always have much lower solvent consumption compared to larger particles.The second process optimization was performed with a fixed column volume, but the column geometry was variable. The results shows that the productivity obtained for the smaller packing particles materials was higher compared to the large for all allowed pressure drops. The productivity obtained for the small particle compared to the large increased by 25-300 % while maintaining 50-300 % less solvent consumption for the purification of the first enantiomer.The addition of TEA seems to be unfavorable for all tested conditions.In conclusion, the optimization of the enantioseparation of omeprazole has been shown to be dependent on column packing particle size as well as column geometry. It has been demonstrated that all parameters need to be simultaneously optimized to reach a global productivity optima.

  • 194.
    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.
    Forssén, Patrik
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Preparative Separation of Omeprazole: Predictions of the Optimal Experimental Conditions by Computer Simulations2011Conference paper (Refereed)
    Abstract [en]

    In this study, omeprazole was used as a model compound. Omeprazole and other related sulfoxide benzimidazoles are used against gastric ulcers and have been extensively studied regarding chromatographic resolution techniques using several different chiral stationary phases.First, AstraZeneca launched Losec, a racemic mixture of RS-omeprazole. Facing loss of patent, the more potent S-enantiomer was developed and marketed as Nexium. Now the patent of Nexium is close expiration why methods for isolation of the pure S-enantiomer will be of importance for the generic pharmaceutical companies.The experimental model separation system represents a system with good selectivity and high solubility of the solute in the eluent. In this investigation the productivity optima for three different particle sizes (5, 10 and 25 µm) at maximum system pressure ranging from 50 to 400 bars are studied. Two different optimizations cases were studied in depth. First,a process optimization with fixed column geometry is studied. The results clearly show that larger packing materials have higher productivity at low pressure drops on the analytical size column.With increasing allowed pressure drops, over 200 bar, the smaller packing materials have substantially higher productivity.The results also show that smaller packing material will always have much lower solvent consumption compared to larger particles.The second process optimization was performed with a fixed column volume, but the column geometry was variable. The results shows that the productivity obtained for the smaller packing particles materials was higher compared to the large for all allowed pressure drops. The productivity obtained for the small particle compared to the large increased by 25-300 % while maintaining 50-300 % less solvent consumption for the purification of the first enantiomer.The addition of TEA seems to be unfavorable for all tested conditions.In conclusion, the optimization of the enantioseparation of omeprazole has been shown to be dependent on column packing particle size as well as column geometry. It has been demonstrated that all parameters need to be simultaneously optimized to reach a global productivity optima.

  • 195.
    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.
    Undin, Torgny
    A Deeper Investigation of Strange Preparative Band Shapes of a Simple Racemic Solute on tris-(3, 5- dimethylphenyl)carbamoyl Cellulose as Chiral Stationary Phase2011Conference paper (Refereed)
    Abstract

    The adsorption equilibria of racemic methyl mandelate on a tris-(3, 5-dimethylphenyl)carbamoyl cellulose chiral stationary phase (CSP) has a peculiar behavior. The preparative band shape of the more retained enantiomer was very unusual with an inflection point at low concentrations whereas the less retained enantiomer shows normal type I adsorption behavior. For a deeper understanding of this separation adsorption isotherms were determined and further analyzed with Scatchard plots combined with adsorption energy distribution calculations. The less retained enantiomer was best described by Tóth adsorption isotherm while the second enantiomer was best described with a bi-Moreau adsorption isotherm. The Moreau model is an extension of the Langmuir model including non-ideal adsorbate-adsorbate interactions; here the unusual model provided 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 by synthetically generated raw adsorption slope data. It was demonstrated 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 it was found to be exothermic; in addition, the non-ideal adsorbate-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

  • 196.
    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.

  • 197.
    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

  • 198.
    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.

  • 199. Eriksson, Björn
    et al.
    Andersson, M.B.O.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Deviation from Ohm's law in electric field assisted capillary liquid chromatography2003In: J. Chromatogr. A, 1010 (2003) 17-24Article in journal (Refereed)
  • 200. Eriksson, Björn
    et al.
    Andersson, M.B.O.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Flow splitting at the inlet electrode as a method for increasing the usable electric field in electric field assisted capillary liquid chromatography2006In: J. Chromatogr. A, J. Chromatogr. A, 1119 (2006) 170-175Article in journal (Refereed)
1234567 151 - 200 of 412
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