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  • 1. Abel, S
    et al.
    Bäbler, Matthäus
    ETH, Inst Chem & Bioengn, Dept Chem & Appl Biosci.
    Arpagaus, C
    Mazzotti, M
    Stadler, J
    Two-fraction and three-fraction continuous simulated moving bed separation of nucleosides2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1043, no 2, p. 201-210Article in journal (Refereed)
    Abstract [en]

     A new experimental set-up and a new simulated moving bed (SMB) operation are presented in this work. A desktop SMB unit developed as a modification of the commercial AKTA(TM) explorer working platform has been utilized for the separation of different mixtures of nucleosides. Both two fraction and three fraction SMB separations have been carried out, the latter made possible by the adoption of a new SMB configuration and operating mode (three fraction SMB, 3F-SMB, operation). Experiments demonstrate the feasibility of the 3F-SMB operation, and confirm the trends predicted based on considerations about retention of the components to be separated along the unit. 

  • 2.
    Agaton, Charlotta
    et al.
    KTH, Superseded Departments, Biotechnology.
    Falk, Ronny
    KTH, Superseded Departments, Biotechnology.
    Uhlén, Mathias
    KTH, Superseded Departments, Biotechnology.
    Hober, Sophia
    KTH, Superseded Departments, Biotechnology.
    Selective enrichment of monospecific polyclonal antibodies for antibody-based proteomics efforts2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1043, p. 33-40Article in journal (Refereed)
    Abstract [en]

    A high stringency protocol, suitable for systematic purification of polyclonal antibodies, is described. The procedure is designed to allow the generation of target protein-specific antibodies suitable for functional annotation of proteins. Antibodies were generated by immunization with recombinantly produced affinity-tagged target proteins. To obtain stringent recovery of the antibodies, a two-step affinity chromatography principle was devised to first deplete the affinity tag-specific antibodies followed by a second step for affinity capture of the target protein-specific antibodies. An analytical dot-blot array system was developed to analyze the cross-reactivity of the affinity-purified antibodies. The results suggest that the protocol can be used in a highly parallel and automated manner to generate mono-specific polyclonal antibodies for large-scale, antibody-based proteomics efforts, i.e. affinity proteomics.

  • 3.
    Agmo Hernández, Víctor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Samuelsson, Jörgen
    Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
    Forssén, Patrik
    Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
    Fornstedt, Torgny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry. Department of Engineering and Chemical Sciences, Karlstad University, SE-651 88 Karlstad, Sweden.
    Enhanced interpretation of adsorption data generated by liquid chromatography and by modern biosensors2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1317, no SI, p. 22-31Article in journal (Refereed)
    Abstract [en]

    In this study we demonstrate the importance of proper data processing in adsorption isotherm estimations. This was done by investigating and reprocessing data from five cases on two closely related platforms: liquid chromatography (LC) and biosensors. The previously acquired adsorption data were reevaluated and reprocessed using a three-step numerical procedure: (i) preprocessing of adsorption data, (ii) adsorption data analysis and (iii) final rival model fit. For each case, we will discuss what we really measure and what additional information can be obtained by numerical processing of the data. These cases clearly demonstrate that numerical processing of LC and biosensor data can be used to gain deeper understanding of molecular interactions with adsorption media. This is important because adsorption data, especially from biosensors, is often processed using old and simplified methods.

  • 4. Albertsson, A-C.
    et al.
    Barenstedt, C.
    Karlsson, S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Solid-phase extraction and gas chromatographic-mass spectrometric identification of degradation products from enhanced environmentally degradable polyethylene1995In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 690, no 2, p. 207-217Article in journal (Refereed)
  • 5.
    Aldaeus, Fredrik
    et al.
    KTH.
    Lin, Yuan
    KTH.
    Amberg, Gustav
    KTH.
    Roeraade, Johan
    KTH.
    Multi-step dielectrophoresis for separation of particles2006In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1131, no 1-2, p. 261-266Article in journal (Refereed)
    Abstract [en]

    A new concept for separation of particles based on repetitive dielectrophoretic trapping and release in a flow system is proposed. Calculations using the finite element method have been performed to envision the particle behavior and the separation effectiveness of the proposed method. As a model system, polystyrene beads in deionized water and a micro-flow channel with arrays of interdigited electrodes have been used. Results show that the resolution increases as a direct function of the number of trap-and-release steps, and that a difference in size will have a larger influence on the separation than a difference in other dielectrophoretic properties. About 200 trap-and-release steps would be required to separate particles with a size difference of 0.2%. The enhanced separation power of dielectrophoresis with multiple steps could be of great importance, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity, or for separations based on combinations of difference in size and dielectric properties.

  • 6.
    Aldaeus, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Lin, Yuan
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Amberg, Gustav
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Roeraade, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Multi-step dielectrophoresis for separation of particles2006In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1131, no 1-2, p. 261-266Article in journal (Refereed)
    Abstract [en]

    A new concept for separation of particles based on repetitive dielectrophoretic trapping and release in a flow system is proposed. Calculations using the finite element method have been performed to envision the particle behavior and the separation effectiveness of the proposed method. As a model system, polystyrene beads in deionized water and a micro-flow channel with arrays of interdigited electrodes have been used. Results show that the resolution increases as a direct function of the number of trap-and-release steps, and that a difference in size will have a larger influence on the separation than a difference in other dielectrophoretic properties. About 200 trap-and-release steps would be required to separate particles with a size difference of 0.2%. The enhanced separation power of dielectrophoresis with multiple steps could be of great importance, not only for fractionation of particles with small differences in size, but also for measuring changes in surface conductivity, or for separations based on combinations of difference in size and dielectric properties.

  • 7.
    Aldaeus, Fredrik
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thewalim, Yasar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Prediction of retention times and peak widths in temperature-programmed gas chromatography using the finite element method2009In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 1, p. 134-139Article in journal (Refereed)
    Abstract [en]

    Optimization of separations in gas chromatography is often a time-consuming task. However, computer simulations of chromatographic experiments may greatly reduce the time required. In this study, the finite element method was used to predict the retention times and peak widths of three analytes eluting from each of four columns during chromatographic separations with two temperature programs. The data acquired were displayed in predicted chromatograms that were then compared to experimentally acquired chromatograms. The differences between the predicted and measured retention times were typically less than 0.1%, although the experimental peak widths were typically 10% larger than expected from the idealized calculations. Input data for the retention and peak dispersion calculations were obtained from isothermal experiments, and converted to thermodynamic parameters.

  • 8.
    Amirkhani, Ardeshir
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Wetterhall, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Nilsson, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Danielsson, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
    Comparison between different sheathless electrospray emitter configurations regarding the performance of nanoscale liquid chromatography time-of-flight mass spectrometry analysis2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1033, no 2, p. 257-266Article in journal (Refereed)
    Abstract [en]

    Four different sheathless electrospray ionization (ESI) configurations were investigated for a nano liquid chromatography (LC) system. The studied configurations were: a column with an integrated emitter, with the ESI potential applied before or after the column, and a column with separate emitter, with the ESI voltage applied at a union before the emitter or at the emitter tip. The results indicates that the efficiency of the LC system is rather independent of the configuration when using 95 μm i.d. columns, acetic mobile phase and standard peptides as a sample. Introduction of post column dead volume seems not to be a critical issue at least with flow rates down to 600 nl/min.

  • 9. Anderson, M. E.
    et al.
    Aslan, D.
    Clarke, A.
    Roeraade, Johan
    KTH, Superseded Departments, Chemistry.
    Hagman, G.
    Evaluation of generic chiral liquid chromatography screens for pharmaceutical analysis2003In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1005, no 02-jan, p. 83-101Article in journal (Refereed)
    Abstract [en]

    Two different automated generic liquid chromatography screens for the separation of chiral compounds of pharmaceutical interest have been evaluated. The test set comprised 53 chemically diverse chiral compounds involving 55 enantiomeric pairs from the pharmaceutical industry (i.e. starting materials, synthetic intermediates and drug substances). The first screen utilised four polysaccharide-based columns with five mobile phases and showed enantioselectivity for 87% of the test compounds. The second screen employed three macrocyclic glycopeptide columns with two mobile phases and showed enantioselectivity for 65% of the test compounds. Merging of the two screening procedures resulted in an enantioselectivity for 96% of the chiral compounds. It is anticipated that the systematic use of the automated chiral HPLC screens described in this report will substantially reduce the necessary time for method development of pharmaceutically related chiral analytical methods.

  • 10. ANDERSSON, B
    et al.
    SANDBERG, G
    IDENTIFICATION OF ENDOGENOUS N-(3-INDOLEACETYL)ASPARTIC ACID IN SCOTS PINE (PINUS-SYLVESTRIS L) BY COMBINED GAS CHROMATOGRAPHY-MASS SPECTROMETRY, USING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY FOR QUANTIFICATION1982In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 238, no 1, p. 151-156Article in journal (Refereed)
  • 11.
    Andersson, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    On-line gas chromatographic analysis of higher alcohol synthesis products from syngas2012In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1247, p. 134-145Article in journal (Refereed)
    Abstract [en]

    An on-line gas chromatographic (GC) system has been developed for rapid and accurate product analysis in catalytic conversion of syngas (a mixture of H-2 and CO) to alcohols, so called "higher alcohol synthesis (HAS)". Conversion of syngas to higher alcohols is an interesting second step in the route of converting coal, natural gas and possibly biomass to liquid alcohol fuel and chemicals. The presented GC system and method are developed for analysis of the products formed from syngas using alkali promoted MoS2 catalysts, however it is not limited to these types of catalysts. During higher alcohol synthesis not only the wanted short alcohols (similar to C-2-C-5) are produced, but also a great number of other products in smaller or greater amounts, they are mainly short hydrocarbons (olefins, paraffins, branched, non-branched), aldehydes, esters and ketones as well as CO2, H2O. Trace amounts of sulfur-containing compounds can also be found in the product effluent when sulfur-containing catalysts are used and/or sulfur-containing syngas is feed. In the presented GC system, most of them can be separated and analyzed within 60 min without the use of cryogenic cooling. Previously, product analysis in "higher alcohol synthesis" has in most cases been carried out partly on-line and partly off-line, where the light gases (gases at room temp) are analyzed on-line and liquid products (liquid at room temp) are collected in a trap for later analysis off-line. This method suffers from many drawbacks compared to a complete on-line GC system. In this paper an on-line system using an Agilent 7890 gas chromatograph equipped with two flame ionization detectors (FID) and a thermal conductivity detector (TCD), together with an Agilent 6890 with sulfur chemiluminescence dual plasma detector (SCD) is presented. A two-dimensional GC system with Deans switch (heart-cut) and two capillary columns (HP-FFAP and HP-Al2O3) was used for analysis of the organic products on the FIDs. Light inorganic gases (H-2, CO, CO2, N-2) and methane were separated on packed columns and quantified with the TCD. The "sulfur GC" was optimized for on-line trace level sulfur analysis in hydrocarbon matrices and used to understand to which degree sulfur is released from the catalyst and incorporated into the liquid product, and if so in which form. The method provides excellent quantitative measurements with a carbon material balance near 99.5% (carbon in/carbon out) for individual measurement points.

  • 12.
    Arnell, Robert
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Surface Biotechnology. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
    Forssén, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing.
    Fornstedt, Torgny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Surface Biotechnology. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Surface Biotechnology.
    Accurate and rapid estimation of adsorption isotherms in liquid chromatography using the inverse method on plateaus2005In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1099, p. 167-174Article in journal (Refereed)
  • 13. Arnell, Robert
    et al.
    Forssén, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Fornstedt, Torgny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Sardella, Roccaldo
    Laemmerhofer, Michael
    Lindner, Wolfgang
    Adsorption behaviour of a quinidine carbamate-based chiral stationary phase: Role of the additive2009In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 16, p. 3480-3487Article in journal (Refereed)
    Abstract [en]

    In this study, we incorporate the additive properties into the theoretical model of a general preparative chromatographic system; this is normally not done and this limits a proper process optimization. As a model phase system, we used the adsorption of 9H-fluoren-9-ylmethoxycarbonyl-allylglycine (Fmoc-allylglycine) enantiomers on a quinidine carbamate-based chiral stationary phase (anion exchanger) together with a methanol-glacial acetic acid-ammonium acetate eluent. The inverse method was used to measure the competitive adsorption isotherms of both the Fmoc-allylglycine enantiomers as well as the non-detectable additive acetic acid. It was concluded that this enantioselective preparative system is well described by a non-heterogeneous adsorption model and that the loading capacity is very high. The proposed model is valid over a wide range of additive concentrations, which is important for process optimization.

  • 14. Arshadi, Mehrdad
    et al.
    Nilsson, Calle
    Magnusson, Bengt
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gas chromatography-mass spectrometry determination of the pentafluorobenzoyl derivative of methylhydrazine in false morel (Gyromitra esculenta) as a monitor for the content of the toxin gyromitrin2006In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1125, no 2, p. 229-233Article in journal (Refereed)
    Abstract [en]

    The main toxic compound found in false morel (Gyromitra esculenta) is acetaldehyde-N-methyl-N-formylhydrazone (gyromitrin). This paper describes a method of determining the total hydrazones content based on acid hydrolysis of gyromitrin and other related hydrazones in air-dried false morel followed by derivatisation of methylhydrazine with pentafluorobenzoyl chloride. The derivative, tris-pentafluorobenzoyl methylhydrazine (tris-PFB-MH) is analyzed by gas chromatography–mass spectrometry. The overall precision of the method is better than 10% (relative standard deviation) for 0.5 ng/μl methylhydrazine in solution. The minimum detectable concentration of methylhydrazine (tris-PFB-MH) by this method is estimated to be approximately 12 pg/μl, which is equal to 0.3 μg/g dry matter (DM) of false morel.

  • 15.
    Arvidsson, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Johannesson, Nina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Citterio, Attilio
    Righetti, Pier Giorgio
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    High throughput analysis of tryptophan metabolites in a complex matrix using capillary electrophoresis coupled to time-of-flight mass spectrometry2007In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1159, no 1-2, p. 154-158Article in journal (Refereed)
    Abstract [en]

    A capillary electrophoresis method for separation and detection with time-of-flight mass spectrometry is described for tryptophan metabolites in the kynurenic pathway. Tryptophan metabolites are usually difficult to detect with electrospray mass spectrometry since they have low surface activity and occur in low nanomolar to micromolar range in body fluids. Modification of the silica-wall with 1-(4-iodobutyl)4-aza-1-azoniabicyclo[2,2,2]octane iodide, also named M7C4I, has successfully been used to deactivate the fused silica wall and generate a stable reversed electroosmotic flow. Utilizing this advantage together with electrospray ionization time-of-flight mass spectrometry, which generates high resolution and fast acquisition monitoring of species, proved to be successful even for such a complex matrix like human cerebrospinal fluid.

  • 16.
    Asberg, Dennis
    et al.
    Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden..
    Weinmann, Annika Langborg
    AstraZeneca, Resp Inflammat & Autoimmun, Innovat Med & Early Dev Biotech Unit, SE-43183 Molndal, Sweden..
    Leek, Tomas
    AstraZeneca, Resp Inflammat & Autoimmun, Innovat Med & Early Dev Biotech Unit, SE-43183 Molndal, Sweden..
    Lewis, Richard J.
    AstraZeneca, Resp Inflammat & Autoimmun, Innovat Med & Early Dev Biotech Unit, SE-43183 Molndal, Sweden..
    Klarqvist, Magnus
    AstraZeneca, Resp Inflammat & Autoimmun, Innovat Med & Early Dev Biotech Unit, SE-43183 Molndal, Sweden..
    Lesko, Marek
    Rzeszow Univ Technol, Dept Chem & Proc Engn, PL-35959 Rzeszow, Poland..
    Kaczmarski, Krzysztof
    Rzeszow Univ Technol, Dept Chem & Proc Engn, PL-35959 Rzeszow, Poland..
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden..
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013). Karlstad Univ, Dept Engn & Chem Sci, SE-65188 Karlstad, Sweden..
    The importance of ion-pairing in peptide purification by reversed-phase liquid chromatography2017In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1496, p. 80-91Article in journal (Refereed)
    Abstract [en]

    The adsorption mechanism for three peptides was studied under overloaded conditions through adsorption isotherm measurements in the presence of an ion-pairing reagent, trifluoroacetic acid (TFA), on an end-capped C18-bonded stationary phase. The overall aim of the study was to obtain a better understanding of how the acetonitrile and the TFA fractions in the eluent affected the overloaded elution profiles and the selectivity between peptides using mechanistic modelling and multivariate design of experiments. When studying the effect of TFA, direct evidence for ion pair formation between a peptide and TFA in acetonitrile-water solutions was provided by fluorine-proton nuclear Overhauser NMR enhancement experiments and the adsorption of TFA on the stationary phase was measured by frontal analysis. The adsorption isotherms for each peptide were then determined by the inverse method at eight TFA concentrations ranging from 2.6 mM to 37.3 mM (0.02–0.29 vol-%) in isocratic elution. The equilibrium between the peptide ion and the peptide-TFA complex was modelled by coupling the mass-balance to reaction kinetics and determining separate adsorption isotherms for the two species. We found that a Langmuir isotherm described the elution profile of peptide-TFA complex well while the peptide ion was described by a bi-Langmuir adsorption isotherm since it exhibited strong secondary interactions. The elution profiles had an unfavorable shape at low TFA concentrations consisting of a spike in their front and a long tailing rear due to the secondary interactions for the peptide ion having very low saturation capacity. The acetonitrile dependence on the adsorption isotherms was studied by determination of adsorption isotherms directly from elution profiles obtained in gradient elution which enabled a broad acetonitrile interval to be studied. Here, it was found that the column saturation capacity was quickly reached at very low acetonitrile fractions and that there were significant variations in adsorption with the molecular weight. Finally, practical implications for method development are discussed based on an experimental design where gradient slope and TFA concentrations are used as factors. (c) 2017 Published by Elsevier B.V.

  • 17.
    Avagyan, Rozanna
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Sadiktsis, Ioannis
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Thorsen, Gunnar
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Östman, Conny
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Determination of benzothiazole and benzotriazole derivates in tire and clothing textile samples by high performance liquid chromatography-electrospray ionization tandem mass spectrometry2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1307, p. 119-125Article in journal (Refereed)
    Abstract [en]

    A high performance liquid chromatography–tandem mass spectrometry method utilizing electrospray ionization in positive and negative mode has been developed for the separation and detection of benzothiazole and benzotriazole derivates. Ultra-sonication assisted solvent extraction of these compounds has also been developed and the overall method demonstrated on a selected clothing textile and an automobile tire sample. Matrix effects and extraction recoveries, as well as linearity and limits of detection have been evaluated. The calibration curves spanned over more than two orders of magnitude with coefficients of correlation R2 > 0.99 and the limits of detection and the limits of quantification were in the range 1.7–58 pg injected and 18–140 pg/g, respectively. The extraction recoveries ranged between 69% and 102% and the matrix effects between 75% and 101%. Benzothiazole and benzotriazole derivates were determined in the textile sample and benzothiazole derivatives determined in the tire sample with good analytical performance.

  • 18.
    Bak, Søren Alex
    et al.
    Eurofins Denmark A/S, Environment, Vejen.
    Hansen, Martin
    Department of Civil & Environmental Engineering, Stanford University.
    Pedersen, Kenneth Munk
    Halling-Sørensen, Bent
    Björklund, Erland
    Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Plattformen för molekylär analys. Kristianstad University, Faculty of Natural Science, Avdelningen för miljö- och biovetenskap. Kristianstad University, Faculty of Natural Science, Research environment MoLab.
    Quantification of four ionophores in soil, sediment and manure using pressurised liquid extraction2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1307, no September, p. 27-33Article in journal (Refereed)
    Abstract [en]

    A multi-residue pressurised liquid extraction (PLE) methodology has been established for the determination of the four ionophores: lasalocid, monensin, salinomycin and narasin in solid environmental matrices. The PLE methodology is combined with solid phase extraction as clean-up using liquid chromatography coupled to tandem mass spectrometry applying electrospray ionisation for detection. The samples were freeze-dried prior to extraction. The absolute recoveries for soil and sediment ranged from 71 to 123% (relative standard deviation (RSDs) below 16%) and in the range 94–133% (RSDs 9–35%) for poultry manure. The final method allowed for the detection of four ionophores down to a few hundred ng kg−1 in natural solid matrices with limit of quantifications (LOQs) being 0.96, 0.87, 0.98, and 0.64 μg kg−1 in soil for lasalocid, monensin, salinomycin, and narasin, respectively. Corresponding LOQs in sediment were 1.28, 1.34, 1.39, and 0.78 μg kg−1 for the respective ionophores, while in manure the LOQs were 0.98, 1.01, 1.45, and 1.01 μg kg−1.

  • 19.
    Barclay, Victoria K. H.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Tyrefors, Niklas L.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Johansson, I. Monika
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Pettersson, Curt E.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Trace analysis of fluoxetine and its metabolite norfluoxetine: Part I: Development of a chiral liquid chromatography-tandem mass spectrometry method for wastewater samples2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 33, p. 5587-5596Article in journal (Refereed)
    Abstract [en]

    An enantioselective method for the determination of fluoxetine (a selective serotonin reuptake inhibitor) and its pharmacologically active metabolite norfluoxetine has been developed for raw and treated wastewater samples. The stable isotope-labeled fluoxetine and norfluoxetine were used in an extended way for extraction recovery calculations at trace level concentrations in wastewater. Wastewater samples were enriched by solid phase extraction (SPE) with Evolute CX-50 extraction cartridges. The obtained extraction recoveries ranged between 65 and 82% in raw and treated wastewater at a trace level concentration of 50 pM (15-16 ng L(-1)). The target compounds were identified by the use of chiral liquid chromatography tandem mass spectrometry (LC-MS/MS) in selected reaction monitoring (SRM) mode. The enantiomers were successfully resolved on a chiral alpha(1)-acid glycoprotein column (chiral AGP) with acetonitrile and 10 mM ammonium acetate buffer at pH 4.4 (3/97, v/v) as the mobile phase. The effects of pH, amount of organic modifier and buffer concentration in the mobile phase were investigated on the enantiomeric resolution (R(s)) of the target compounds. Enantiomeric R(s)-values above 2.0 (1.03 RSD%, n = 3) were achieved for the enantiomers of fluoxetine and norfluoxetine in all mobile phases investigated. The method was validated by assessing parameters such as cross-contamination and carryover during SPE and during LC analysis. Cross-talk effects were examined during the detection of the analytes in SRM mode. In addition, the isotopic purity of fluoxetine-d(5) and norfluoxetine-d(5) were assessed to exclude the possibility of self-contamination. The interassay precision of the chromatographic separation was excellent, with relative standard deviations (RSD) equal to or lower than 0.56 and 0.81% in raw and treated wastewaters, respectively. The method detection and quantification limits (respectively, MDL and MQL) were determined by the use of fluoxetine-d5 and norfluoxetine-d5. The MQL for the single enantiomers ranged from 12 to 14 pM (3.6-4.3 ng L(-1)) in raw wastewater and from 3 to 4 pM (0.9-1 ng L(-1)) in treated wastewater. The developed method has been employed for the quantification of (R)-fluoxetine, (S)-fluoxetine and the enantiomers of norfluoxetine in raw and treated wastewater samples to be presented in Part II of this study.

  • 20.
    Barclay, Victoria K H
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Tyrefors, Niklas L
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Johansson, I Monika
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Pettersson, Curt E
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Trace analysis of fluoxetine and its metabolite norfluoxetine. Part II: Enantioselective quantification and studies of matrix effects in raw and treated wastewater by solid phase extraction and liquid chromatography-tandem mass spectrometry2012In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1227, p. 105-114Article in journal (Refereed)
    Abstract [en]

    The isotope-labeled compounds fluoxetine-d5 and norfluoxetine-d5 were used to study matrix effects caused by co-eluting compounds originating from raw and treated wastewater samples, collected in Uppsala, Sweden. The matrix effects were investigated by the determination of matrix factors (MF) and by a post-column infusion method. The matrix factors were determined to be 38–47% and 71–86% for the enantiomers of norfluoxetine-d5 and fluoxetine-d5, respectively. The influence of matrix effects when quantifying the enantiomers of the active pharmaceutical ingredient and the metabolite in wastewater samples with LC–MS/MS is discussed and methods to overcome the problem are presented. The enantiomeric concentrations of fluoxetine and its human metabolite norfluoxetine, quantified by a one-point calibration method, were 12–52 pM (3.5–16 ng L−1) in raw wastewater and 4–48 pM (1.2–15 ng L−1) in treated wastewater. Furthermore, the calculated enantiomeric fractions (EF) of the substances were found to be between 0.68 and 0.71 in both matrices. Neither the EF values for fluoxetine nor those for norfluoxetine were significantly different in the raw wastewater compared to the treated wastewater. Interestingly, the concentration of (S)-fluoxetine was found to be higher than the concentration of (R)-fluoxetine in both raw and treated wastewater. These results are different from other results presented in the literature, which shows that the relative concentrations of the enantiomers of a chiral active pharmaceutical ingredient might be significantly different in wastewater samples from different treatment systems. We report, for the first time, the concentrations of the enantiomers of norfluoxetine in wastewater samples. The concentrations of (S)-norfluoxetine were found to be higher than the concentration of (R)-norfluoxetine in the raw as well as in the treated wastewater samples.

  • 21.
    Barclay, Victoria K.H.
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Tyrefors, Niklas L.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Johansson, I. Monika
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Pettersson, Curt
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Chiral analysis of metoprolol and two of its metabolites, alpha‑hydroxymetoprolol and deaminated metoprolol, in wastewater using liquid chromatography-tandem mass spectrometry2012In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1269, no SI, p. 208-217Article in journal (Refereed)
    Abstract [en]

    A LC–MS/MS method for the chiral separation of metoprolol and two of its main metabolites, α-hydroxymetoprolol (α-OH-Met) and deaminated metoprolol (COOH-Met), in environmental water samples has been developed. The target bases, metoprolol and α-OH-Met, as well as the acidic metabolite (COOH-Met) were extracted from water samples by a solid phase extraction method employing Oasis HLB cartridges. The extraction recoveries were ≥73% for all compounds in surface water. Four different types of chiral stationary phases were investigated for the separation of the eight stereoisomers of metoprolol and its metabolites, Chiralcel OD-H, Chirobiotic V, Chiral AGP and Chiral CBH. In the final method, the enantiomers of metoprolol and four stereoisomers of α-OH-Met were separated using Chiral CBH, the enantiomers of COOH-Met were separated employing Chiral AGP. The analytes were detected in SRM mode by triple quadrupole mass spectrometry. The method was applied for the chiral analysis of the analytes in treated wastewater samples from Uppsala, Sweden. The enantiomers and diastereoisomers of α-OH-Met were detected and analyzed in the samples. The concentrations of the three first eluting stereoisomers of α-OH-Met were between 54 and 61 pM. Interestingly, the last eluting stereoisomer was found to be present at a concentration of 151 pM at the same sampling occasion. This is, to the best of the authors’ knowledge, the first time the stereoisomers of α-OH-Met have been detected in wastewater samples. The enantiomers of metoprolol were determined to be 1.77 and 1.86 nM in the same matrix. The enantiomers of COOH-Met were not detected above the method detection limit (42 pM) in treated wastewater samples. The developed LC–MS/MS methods were validated in wastewater samples.

  • 22.
    Bergström, Sara K.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Goiny, Michel
    Danielsson, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Ungerstedt, Urban
    Andersson, Marit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Markides, Karin E.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Screening of microdialysates taken before and after induced liver damage; on-line solid phase extraction-electrospray ionization-mass spectrometry2006In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1120, no 1-2, p. 21-26Article in journal (Refereed)
    Abstract [en]

    A novel method is described to follow known and unknown compounds in biological processes using microdialysis sampling and mass spectrometric detection. By implementation of internal standard, desalting/enrichment for the sample work-up, and multivariate data analysis, this methodology is a basis for future applications in early diagnosis of diseases and organ damage, as a complement to the routinely used clinical methods for biological samples. The present study includes screening without specific target analytes, of samples collected by microdialysis from liver of anaesthetized rats before and after local damage to this organ. Sample series were classified by principal component analysis, and the stimulation was identified in the chemical patterns produced by the presented analytical tool.

  • 23.
    Björkholm, Eva
    et al.
    Arbetsmiljöinstitutet.
    Hultman, Annika
    Arbetsmiljöinstitutet.
    Rudling, Jan
    Arbetsmiljöinstitutet.
    Determination of chlorine and chlorine dioxide in workplace air by impinger collection and ion-chromatographic analysis1988In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, no 457, p. 409-414Article in journal (Refereed)
  • 24.
    Blomberg, Lars G
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Abdel-Rehim, M
    Recent advances in microextraction by packed sorbent for bioanalysis2010In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1217, no 16, p. 2569-2580Article in journal (Refereed)
  • 25.
    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)
  • 26.
    Bossi, A
    et al.
    University Verona, Department Agriculture and Ind Biotechnol, I-37134 Verona, Italy; Cranfield University, Institute BioScience and Technology, Cranfield MK43 0AL, Beds, England; .
    Piletsky, SA
    University Verona, Department Agriculture and Ind Biotechnol, I-37134 Verona, Italy; Cranfield University, Institute BioScience and Technology, Cranfield MK43 0AL, Beds, England; .
    Righetti, PG
    University Verona, Department Agriculture and Ind Biotechnol, I-37134 Verona, Italy; Cranfield University, Institute BioScience and Technology, Cranfield MK43 0AL, Beds, England; .
    Turner, APF
    Cranfield University, UK.
    Capillary electrophoresis coupled to biosensor detection2000In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 892, no 02-jan, p. 143-153Article in journal (Refereed)
    Abstract [en]

    The present review highlights some modern aspects of biosensor revelation, a detection method which has already found a large number of applications in healthcare, food industry and environmental analysis. First, the concept of bio-recognition, which is at the heart of biosensor technology, is discussed, with emphasis on host-guest-like recognition mechanisms. This detection device has been successfully coupled, in its first applications, to chromatographic columns, which allow a high resolution of complex mixtures of analytes prior to interaction with the biosensing unit. The properties of the transducing elements, which should generate a signal (e.g., electrochemical, thermal, acoustic, optical) of proper intensity and of relative fast rise, are additionally evaluated and discussed. The review then focuses on potential applications of biosensing units in capillary electrophoresis (CE) devices. CE appears to be an excellent separation methodology to be coupled to biosensor detection, since it is based on miniaturized electrophoretic chambers, fast analysis times, complete automation in sample handling and data treatment and requires extremely small sample volumes. Although only a few applications of CE-based biosensors have been described up to the present, it is anticipated that this hyphenated technique could have a considerable expansion in the coming years, (C) 2000 Elsevier Science B.V. All rights reserved.

  • 27.
    Bossi, Alessandra
    et al.
    Department of Science and Technology, University of Verona, Verona, Italy.
    Castelletti, Laura
    Department of Science and Technology, University of Verona, Verona, Italy.
    Piletsky, Sergey A.
    Institute of BioScience and Technology, Cranfield University at Silsoe, Silsoe, Bedfordshire, UK.
    Turner, Anthony P. F.
    Cranfield University, UK.
    Righetti, Pier Giorgio
    Department of Science and Technology, University of Verona, Verona, Italy.
    Properties of poly-aminophenylboronate coatings in capillary electrophoresis for the selective separation of diastereoisomers and glycoproteins2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1023, no 2, p. 297-303Article in journal (Refereed)
    Abstract [en]

    The polymerisation of 3-aminophenylboronic acid (APBA) in aqueous environment has been used for the open tubular modification of capillary electrophoresis (CE) capillaries. Being poly-APBA endowed with boronic acid, aromatic rings and secondary amines groups, it posses a variety of functional groups affecting selectivity. Diastereoisomers (e.g. ascorbic and isoascorbic acid) and proteins (e.g. haemoglobins) were successfully separated onto poly-APBA column, by means of a combination of electrophoresis and open tubular electrochromatography. The mechanism of selection was investigated: results indicate an interplay between enhancing or silencing the contribution of the protonable functionahties (amino groups, boronic acid). The properties of APBA polymer coating make it attractive for CE separation and for further application in affinity separations and chip technologies.

  • 28.
    Bouchet, Sylvain
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Analytical developments for the determination of monomethylmercury complexes with low molecular mass thiols by reverse phase liquid chromatography hyphenated to inductively coupled plasma mass spectrometry2014In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1339, p. 50-58Article in journal (Refereed)
    Abstract [en]

    The behavior of monomethylmercury (MMHg) is markedly influenced by its distribution among complexes with low molecular mass (LMM) thiols but analytical methodologies dedicated to measure such complexes are very scarce up to date. In this work, we selected 15 LMM thiols often encountered in living organisms and/or in the environment and evaluated the separation of the 15 corresponding MMHg-thiol complexes by various high performance liquid chromatography (HPLC) columns. Two C18 (Phenomenex Synergi Hydro-RP and LunaC18(2)), two phenyl (Inertsil Ph 3 and 5 mu m) and one mixed-mode (Restek Ultra IBD) stationary phases were tested for their retention and resolution capacities of the various complexes. The objective was to find simple separation conditions with low organic contents in the mobile phase to provide optimal conditions for detection by inductively coupled plasma mass spectrometry (ICPMS). The 15 complexes were synthesized in solution and characterized by electrospray ionization-mass spectrometry (ESI-MS). The C18 columns tested were either not resolutive enough or too retentive. The 3 pm phenyl stationary phase was able to resolve 10 out of the 15 complexes in less than 25 min, under isocratic conditions. The mixed-mode column was especially effective at separating the most hydrophilic complexes (6 complexes out of the 15), corresponding to the main LMM thiols found in living organisms. The detection limits (DLs) for these two columns were in the low nanomolar range and overall slightly better for the phenyl column. The possibilities offered by such methodology were exemplified by monitoring the time-course concentrations of four MMHg-thiol complexes within a phytoplankton incubation containing MMHg in the presence of an excess of four added thiols. 

  • 29. Brits, Martin
    et al.
    Gorst-Allman, Peter
    Rohwer, Egmont R.
    De Vos, Jayne
    de Boer, Jacob
    Weiss, Jana M.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Swedish University of Agricultural Sciences, Sweden.
    Comprehensive two-dimensional gas chromatography coupled to high resolution time-of-flight mass spectrometry for screening of organohalogenated compounds in cat hair2018In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1536, p. 151-162Article in journal (Refereed)
    Abstract [en]

    The coupling of comprehensive two-dimensional gas chromatography with high-resolution time of-flight mass spectrometry offers the best separation efficiency combined with accurate mass measurements over a wide mass range. The tremendous power of this screening tool is illustrated by trace qualitative screening analysis of organohalogenated compounds (OHCs) in pet cat hair. Tentative identification was supported by mass spectral database searches and elemental formula prediction from the experimentally determined accurate mass data. This screening approach resulted in the first tentative identification of pentabromoethylbenzene, decabromodiphenyl ethane, hexabromocyclododecane, trisbromoneopentyl alcohol, tris(2-chloroethyl) phosphate and tris(2-chloroisopropyl)phosphate in the South African indoor environment. A total of seventy-two OHCs were identified in the samples and include known flame retardants, such as polybrominated diphenyl ethers, and legacy contaminants such as polychlorinated biphenyls and organochlorine, organophosphorous and pyrethroid pesticides. The results obtained from cat hair indicate that these pets are exposed to complex mixtures of OHCs and the detection of these compounds suggests that non-invasive cat hair samples can be used to model indoor exposure with reference to external deposition of OHCs present in the air and dust surrounding people. Toddlers share the same environment as pet cats and therefore also the same health risks.

  • 30.
    Burman, Lina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Solid-Phase Microextraction for Qualitative and Quantitative Determination of Migrated Degradation Products of Antioxidants in an Organic Aqueous Solution2005In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1080, no 2, p. 107-116Article in journal (Refereed)
    Abstract [en]

     Low molecular weight aromatic substances may migrate out from plastic packaging to their contents, especially if they consist of organic aqueous solutions or oils. It is, therefore, extremely important to be able to identify and quantify any migrated substances in such solutions, even at very low concentrations. We have in this work investigated and evaluated the use of solid-phase microextraction for the specific task of extraction from an organic aqueous solution such as a simulated pharmaceutical solution consisting of 10 vol.% ethanol in water. The goal was furthermore to investigate the possibility of simultaneously identifying and quantifying the substances in spite of differences in their chemical structures. Methods were developed and evaluated for extraction both with direct sampling and with headspace sampling. Difficulties appeared due to the ethanol in the solution and the minute amounts of substances present. We have shown that a simultaneous quantification of migrated low molecular weight degradation products of antioxidants using only one fibre is possible if the extraction method and temperature are adjusted in relation to the concentration levels of the analytes. Comparions were made with solid-phase extraction.

  • 31.
    Bylund, Dan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norström, Sara
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Essén, Sofia
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Lundström, Ulla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Analysis of low molecular mass organic acids in natural waters by ion exclusion chromatography tandem mass spectrometry2007In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1176, no 1-2, p. 89-93Article in journal (Refereed)
    Abstract [en]

    A sensitive and selective method for the analysis of aliphatic low molecular mass organic acids (LMMOAs) in natural waters is presented. The method is based on separation with ion exclusion chromatography and detection with electrospray ionization tandem mass spectrometry (LC-MS/MS). The extra selectivity gained by applying MS/MS allows for a minimum of sample preparation and the use of a sub-optimal mobile phase regarding chromatographic resolution. Instead the mobile phase, comprising aqueous formic acid With methanol as organic modifier, was mainly optimized for maximum sensitivity and long term MS stability. Detection limits for malonic, fumaric, maleic, succinic, citraconic, glutaric, malic, alpha-ketoglutaric, tartaric, shikimic, trans-aconitic, cis-aconitic, isocitric and citric acid were in the range 1-50 nM, while the detection limits for pyruvic, oxalic and lactic acid were around 250 nM for an injection volume of 100 mu L. Due to their metal-chelating properties, these LMMOAs are all considered to affect the bioavailability of metals and to be involved in soil forming processes. It is thus of interest to be able to monitor their presence in natural waters, and the method developed within this work was successfully applied for the analysis of LMMOAs in soil solution and stream water samples.

  • 32.
    Bäckström, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Moberg, My
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Sjöberg, Per J. R.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Danielsson, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Multivariate comparison between peptide mass fingerprints obtained by liquid chromatography-electrospray ionization-mass spectrometry with different trypsin digestion procedures2007In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1171, no 1-2, p. 69-79Article in journal (Refereed)
    Abstract [en]

    Peptide mass fingerprints were obtained for three different proteins using three different digestion procedures in triplicates with liquid chromatography coupled to electrospray ionization mass spectrometry. For each protein the results were compared with multivariate data analysis (cluster analysis, kernel principal component analysis) and pair-wise contrast evaluation. Clear systematic differences between the digestion procedures were established for all the proteins. The visual presentation of the pair-wise differences between procedures could to some extent be related to the protein fragments, although the main objective was to identify m/z and retention regions in the original peptide maps that should be subject to further exploration.

  • 33.
    Carrizo, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Grimalt, J.O.
    Gas chromatographic-mass spectrometric analysis of polychlorostyrene congener mixtures in sediments, human sera and cord sera2009In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 30, p. 5723-5729Article in journal (Refereed)
    Abstract [en]

    Complex mixtures of polychlorostyrenes are produced and released into the environment by reaction of chlorine with graphite at high temperatures, e.g. in electrodes. The occurrence of these compounds in the environment or human tissues is often indicative of pollution from electrolytic processes. Combined gas chromatography coupled to electron impact and negative ion chemical ionization mass spectrometry is described here for the analysis of these compounds in sediments, human venous sera and cord sera. This method has allowed a specific congener identification and quantification of the chlorostyrene mixtures present in fluvial sediments polluted by effluents from a chlorine-alkali plant. Besides octachlorostyrene, the mixture of compounds identified involved the six possible heptachlorostyrenes, fifteen hexachlorostyrenes and seven pentachlorostyrenes, having concentrations in the range of 76-16000 ng g(-1) dry weight. In human sera from the Population exposed to airborne emissions from this plant these compounds ranged between 17 and 63 ng L-1 and the distributions were dominated by octachlorostyrene, three heptachlorostyrenes, including beta,beta-2,3,4,5,6-heptachlorostyrene, and alpha-2,3,4,5,6-hexachlorostyrene. Both distribution patterns showed major differences in composition despite the common pollution source that was influencing both types of samples. The method also revealed qualitative differences between maternal and cord sera from the exposed population.

  • 34. Collen, A.
    et al.
    Penttila, M.
    Stalbrand, H.
    Tjerneld, F.
    Veide, Andres
    KTH, Superseded Departments, Biotechnology.
    Extraction of endoglucanase I (Cel7B) fusion proteins from Trichoderma reesei culture filtrate in a poly(ethylene glycol)phosphate aqueous two-phase system2002In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 943, no 1, p. 55-62Article in journal (Refereed)
    Abstract [en]

    Endoglucanases (EGI) (endo-1,4-beta-D-glucan-4-glucanohydrolase, EC 3.2.1.4, Cel7B) of Trichoderma reesei are industrially important enzymes. Thus, there is a great need for development of a primary recovery method suitable for large-scale utilization. In this study we present a concept applicable for large-scale purification of an EGI fusion protein by one-step extraction in a poly(ethylene glycol) PEG-sodium/potassium phosphate aqueous two-phase system. EGI is a two-module enzyme composed of an N-terminal catalytic module and a C-terminal cellulose binding module (CBM) separated by a glycosylated linker region. Partitioning of six different EGI constructs, containing the C-terminal extensions (WP)(2), (WP)(4) or the amphiphilic protein hydrophobin I (HFB) of T. reesei instead of the CBM were studied to evaluate if any of the fusions could improve the partition coefficient sufficiently to be suitable for large-scale production. All constructs showed improved partitioning in comparison to full length EGI. The (WP)(4) extensions resulted in 26- to 60-fold improvement of partition coefficient. Consequently, a relative minor change in amino acid sequence on the two-module protein EGI improved the partition coefficient significantly in the PEG 4000-sodium/potassium phosphate system. The addition of HFBI to EGI clearly enhanced the partition coefficient (K=1.2) in comparison to full-length EGI (K=0.035). Partitioning of the construct with (WP)(4) fused to the catalytic module and a short sequence of the linker [EGI(core-P5)(WP)(4)] resulted in the highest partition coefficient (K=54) and a yield of 98% in the PEG phase. Gel electrophoresis showed that the construct with the (WP)(4) tag attached after a penta-proline linker could be purified from the other bulk proteins by only a single-step separation in the PEG 4000-sodium/potassium phosphate system. This is a major improvement in comparison with the previously studied model (ethylene oxide-propylene oxide)-dextran system. Hence, this construct will be suitable for further optimization of the extraction of the enzyme in a PEG 4000-sodium/potassium phosphate system from culture filtrate.

  • 35.
    Concheiro, Marta
    et al.
    NIDA, MD 21224 USA.
    Castaneto, Marisol
    NIDA, MD 21224 USA; University of Maryland Baltimore County, MD 21228 USA.
    Kronstrand, Robert
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. National Board Forens Med, Department Forens Genet and Forens Toxicol, Linkoping, Sweden.
    Huestis, Marilyn A.
    NIDA, MD 21224 USA.
    Simultaneous determination of 40 novel psychoactive stimulants in urine by liquid chromatography-high resolution mass spectrometry and library matching2015In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1397, p. 32-42Article in journal (Refereed)
    Abstract [en]

    The emergence of novel psychoactive substances is an ongoing challenge for analytical toxicologists. Different analogs are continuously introduced in the market to circumvent legislation and to enhance their pharmacological activity. Although detection of drugs in blood indicates recent exposure and link intoxication to the causative agent, urine is still the most preferred testing matrix in clinical and forensic settings. We developed a method for the simultaneous quantification of 8 piperazines, 4 designer amphetamines and 28 synthetic cathinones and 4 metabolites, in urine by liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS). Data were acquired in full scan and data dependent MS2 mode. Compounds were quantified by precursor ion exact mass, and confirmed by product ion spectra library matching, taking into account product ions exact mass and intensities. One-hundred pi, urine was subjected to solid phase cation exchange extraction (SOLA SCX). The chromatographic reverse-phase separation was achieved with gradient mobile phase of 0.1% formic acid in water and in acetonitrile in 20 min. The assay was linear from 2.5 or 5 to 500 mu g/L. Imprecision (n = 15) was less than15.4%, and accuracy (n = 15) 84.2-118.5%. Extraction efficiency was 51.2-111.2%, process efficiency 57.7-104.9% and matrix effect ranged from -41.9% to 238.5% (CV less than 23.3%, except MDBZP CV less than 34%). Authentic urine specimens (n = 62) were analyzed with the method that provides a comprehensive confirmation for 40 new stimulant drugs with specificity and sensitivity.

  • 36.
    Courtois, Julien
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fischer, Gerd
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sellergren, Börje
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Molecularly imprinted polymers grafted to flow through poly(trimethylolpropane trimethacrylate) monoliths for capillary-based solid-phase extraction2006In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1109, no 1, p. 92-99Article in journal (Refereed)
    Abstract [en]

    Monolithic previous termmolecularly imprinted polymersnext term (mMIPs) have been synthesized in a novel way using a trimethylolpropane trimethacrylate core material photo-polymerized in situ in a 100 μm I.D. UV-transparent capillary and further photo-previous termgraftednext term to create specific cavities in the previous termgraftednext term layer. This polymerization technique allows the imprints to be directly created on the surface of the material using a minimum amount of template. Three different anaesthetics of similar structures (bupivacaine, mepivacaine and S-ropivacaine) were used as model target molecules to synthesize sample enrichment media. Hence, various mMIPs have been prepared and evaluated on a micro-system against each analyte in order to test the retention properties and cross-selectivities of the materials. The retention factors were determined and compared with the non-previous termimprintednext term reference column (mNIP), yielding high imprinting factors together with good selectivity factors between the three analytes. A study with a pure enantiomeric target was carried out to assess the degree of stereo-specific imprinting for injection of racemic mixtures. Finally, one column was previous termimprintednext term with an equimolar mixture of all three anaesthetics to provide further comprehension of the retention mechanism and accredit the possibility of using the material as a sample enrichment entity. Scanning electron microscopy (SEM), nitrogen absorption/desorption (BET) and mercury intrusion porosimetry were used to characterize the monolith and the mMIPs properties. Nuclear magnetic resonance (NMR) has been used to assess the similarities between the mMIP and mNIP.

  • 37.
    Dahlman, Olof
    et al.
    STFI.
    Jacobs, Anna
    STFI.
    Liljenberg, Annika
    STFI.
    Ismail Olsson, Asha
    STFI.
    Analysis of carbohydrates in wood and pulps employing enzymatic hydrolysis and subsequent capillary zone electrophoresis2000In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 891, no 1, p. 157-174Article in journal (Refereed)
  • 38.
    Danielsson, Conny
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Wiberg, Karin
    Umeå University, Faculty of Science and Technology, Chemistry.
    Korytárb, Peter
    Bergek, Sture
    Umeå University, Faculty of Science and Technology, Chemistry.
    Brinkman, Udo A.Th.
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Chemistry.
    Trace analysis of polychlorinated dibenzo-p-dioxins, dibenzofurans and WHO polychlorinated biphenyls in food using comprehensive two-dimensional gas chromatography with electron-capture detection2005In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1086, no 1-2, p. 61-70Article in journal (Refereed)
    Abstract [en]

    Trace analysis of 2,3,7,8-polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and the 12 WHO-PCBs (four non-ortho and eight mono-ortho congeners that have been assigned toxic equivalence factors, TEFs, by the World Health Organisation) was conducted by comprehensive two-dimensional gas chromatography with a micro electron-capture detector (GC x GC-mu ECD). Four food matrices (fish oil from herring, spiked cows' milk, vegetable oil and an eel extract) were analysed by two GC x GC laboratories, and four GC-HRMS laboratories generated reference values. The two GC x GC laboratories used different column combinations for separating the target analytes. For the first dimension, non-polar DB-XLB and VF-1 columns were used, and for the second dimension, an LC-50 liquid crystalline column with unique selectivity for planar compounds. The congener-specific and total toxic equivalence (TEQ) data obtained using DB-XLB x LC-50 were in good agreement with results obtained by the GC-HRMS laboratories. The WHO-PCB data obtained with the VF-1 x LC-50 combination was also good, but the PCDD/F concentrations were sometimes overestimated due to matrix interferences. GC x GC-mu ECD using DB-XLB x LC-50 seems to fulfil the European Community requirements of a screening method for PCDD/F and WHO-PCB TEQ in food.

  • 39. Daszykowski, M.
    et al.
    Danielsson, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Walczak, B.
    No-alignment-strategies for exploring a set of two-way data tables obtained from capillary electrophoresis-mass spectrometry2008In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1192, no 1, p. 157-165Article in journal (Refereed)
    Abstract [en]

    Hyphenated techniques such as capillary electrophoresis-mass spectrometry (CE-MS) or high-performance liquid chromatography with diode array detection (HPLC-DAD), etc., are known to produce a huge amount of data since each sample is characterized by a two-way data table. In this paper different ways of obtaining sample-related information from a set of such tables are discussed. Working with original data requires alignment techniques due to time shifts caused by unavoidable variations in separation conditions. Other pre-processing techniques have been suggested to facilitate comparison among samples without prior peak alignment, for example, 'binning' and/or 'blurring' the data along the time dimension. All these techniques, however, require optimization of some parameters, and in this paper an alternative parameter-free method is proposed. The individual data tables (X) are represented as Gram matrices (XXT), where the summation is taken over the time dimension. Hence the possible variations in time scale are eliminated, while the time information is at least partly preserved by the correlation structure between the detection channels. For comparison among samples, a similarity matrix is constructed and explored by principal component analysis and hierarchical clustering. The Gram matrix approach was tested and compared to some other methods using 'binned' and 'blurred' data for a data set with CE-MS runs on urine samples. In addition to data exploration by principal component analysis and hierarchical clustering, a discriminant partial least squares model was constructed to discriminate between the samples that were taken with and without the prior intake of a drug. The result showed that the proposed method is at least as good as the others with respect to cluster identification and class prediction. A distinct advantage is that there is no need for parameter optimization, while a potential drawback is the large size of the Gram matrices for data with high mass resolution.

  • 40. de Boer, Jacob
    et al.
    van Bavel, Bert
    Örebro University, School of Science and Technology.
    Special Issue Tools for the Reach Programme - Analytical Methods for the Evaluation of Industrial Contaminants: Foreword2009In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 3, p. 301-301Article in journal (Refereed)
  • 41.
    Dinh, Ngoc Phuoc
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jonsson, Tobias
    Merck SeQuant AB, Box 7956, S-90719 Umeå, Sweden.
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Probing the interaction mode in hydrophilic interaction chromatography2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 35, p. 5880-5891Article in journal (Refereed)
    Abstract [en]

    This work aims at characterizing interactions between a select set of probes and 22 hydrophilic and polar commercial stationary phases, to develop an understanding of the relationship between the chemical properties of those phases and their interplay with the eluent and solutes in hydrophilic interaction chromatography. "Hydrophilic interaction" is a somewhat inexact term, and an attempt was therefore made to characterize the interactions involved in HILIC as hydrophilic, hydrophobic, electrostatic, hydrogen bonding, dipole-dipole, π-π interaction, and shape-selectivity. Each specific interaction was quantified from the separation factors of a pair of similar substances of which one had properties promoting the interaction mode being probed while the other did not. The effects of particle size and pore size of the phases on retention and selectivity were also studied. The phases investigated covered a wide range of surface functional groups including zwitterionic (sulfobetaine and phosphocholine), neutral (amide and hydroxyl), cationic (amine), and anionic (sulfonic acid and silanol). Principal component analysis of the data showed that partitioning was a dominating mechanism for uncharged solutes in HILIC. However, correlations between functional groups and interactions were also observed, which confirms that the HILIC retention mechanism is partly contributed by adsorption mechanisms involving electrostatic interaction and multipoint hydrogen bonding. Phases with smaller pore diameters yielded longer retention of solutes, but did not significantly change the column selectivities. The particle diameter had no significant effect, neither on retention, nor on the selectivities. An increased water content in the eluent reduced the multipoint hydrogen bonding interactions, while an increased electrolyte concentration lowered the selectivities of the tested columns and made their interaction patterns more similar.

  • 42.
    Dinh, Ngoc Phuoc
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Merck SeQuant AB, Umeå.
    Jonsson, Tobias
    Merck SeQuant AB, Umeå.
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Water uptake on polar stationary phases under conditions for hydrophilic interaction chromatography and its relation to solute retention2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1320, p. 33-47Article in journal (Other academic)
    Abstract [en]

    In hydrophilic interaction chromatography, water is known to accumulate on the stationary phase to form a water enriched layer, which is believed to play an important role in the retention mechanism. To gain a better understanding retention mechanism in HILIC, we have determined the water uptake on twelve different HILIC stationary phases. Non-modified and monomerically functionalized silica phases followed a pattern of monolayer formation followed by multiple layer adsorption, while the water uptake on polymerically functionalized silica stationary phase showed the characteristics of formation and swelling of hydrogels. This difference in the nature of water accumulation was found to be related to different water uptake patterns when methanol and tetrahydrofuran were added to 80:20 % (v/v) acetonitrile/water by replacing 5 % of the acetonitrile as tertiary solvents, and also when ammonium acetate was added as buffering electrolyte. The relationship between water uptake and retention mechanism was investigated by looking at the correlation between retention factors of neutral analytes and phase ratios of HILIC columns, calculated either as surface area (adsorption) or volume of the water layer enriched from the acetonitrile/water eluent (partitioning). Regardless of the adsorption or partitioning mechanism, the interaction of neutral analytes and stationary phase could be mainly the hydrogen bonding between analytes and the accumulated water in the water enriched layer.

  • 43.
    Do, Lan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Geladi, Paul
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Multivariate data analysis to characterize gas chromatography columns for dioxin analysis2014In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1347, p. 137-145Article in journal (Refereed)
    Abstract [en]

    Principal component analysis (PCA) was applied for evaluating the selectivity of 22 GC columns for which complete retention data were available for the 136 tetra- to octa-chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). Because the hepta- and octa-homologues are easy to separate the PCA was focused on the 128 tetra- to hexa-CDD/Fs. The analysis showed that 21 of the 22 GC columns could be subdivided into four groups with different selectivity. Group I consists of columns with non-polar thermally stable phases (Restek 5Sil MS and Dioxin 2, SGE BPX-DXN, Supelco Equity-5, and Agilent DB-1, DB-5, DB-5ms, VF-5ms, VF-Xms and DB-XLB). Group II includes ionic liquid columns (Supelco SLB-IL61, SLB-IL111 and SLB-IL76) with very high polarity. Group III includes columns with high-percentage phenyl and cyanopropyl phases (Agilent DB-17 and DB-225, Quadrex CPS-1, Supelco SP-2331, and Agilent CP-Sil 88), and Group IV columns with shape selectivity (Dionex SB-Smectic and Restek LC-50, Supelco beta DEXcst, Agilent VF-Xms and DB-XLB). Thus, two columns appeared in both Group I and IV (Agilent VF-Xms and DB-XLB). The selectivity of the other column, Agilent DB-210, differs from those of these four groups. Partial least squares (PLS) regression was used to correlate the retention times of the tetra- to hexa-CDD/Fs on the 22 stationary phases with a set of physicochemical and structural descriptors to identify parameters that significantly influence the solute-stationary phase interactions. The most influential physicochemical parameters for the interaction were associated with molecular size (as reflects in the total energy, electron energy, core-core repulsion and standard entropy), solubility (aqueous solubility and n-octanol/water partition coefficient), charge distribution (molecular polarizability and dipolar moment), and reactivity (relative Gibbs free energy); and the most influential structural descriptors were related to these parameters, in particular, size and dipolar moment. Finally, the PCA and PLS analyses were complemented with linear regression analysis to identify the most orthogonal column combinations, which could be used in comprehensive two-dimensional gas chromatography (GC x GC) to enhance PCDD/F separation and congener profiling. (C) 2014 Elsevier B.V. All rights reserved.

  • 44.
    Do, Lan
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Liljelind, Per
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Zhang, Jin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Haglund, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Comprehensive profiling of 136 tetra- to octa-polychlorinated dibenzo-p-dioxins and dibenzofurans using ionic liquid columns and column combinations2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1311, p. 157-169Article in journal (Refereed)
    Abstract [en]

    The orders of elution of all 136 tetra- to octa-chlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined on six gas chromatography (GC) columns. Three of these columns had ionic liquid stationary phases (SLB-IL111, SLB-IL76 and SLB-IL61; Supelco), one a liquid crystal phase (LC-50; Restek), one a chiral phase (beta DEXcst; Restek) and one a low bleed non-polar phase (DB-XLB; J&W/Agilent). According to our results, the high polarity and multiple solvation interactions of the ionic liquid stationary phases offered superior resolving power to that achieved with previously evaluated columns. The SLB-IL61 and SLB-IL111 columns resolved or partially separated 106 and 100 congeners, respectively, of the 136 PCDD/Fs. The SLB-IL61 also resolved 15 and partially separated one of the seventeen 2,3,7,8-substituted PCDD/Fs. Additional congeners can be separated by complementary analyses using additional columns in a dual- or triple-column approach. For example, using a combination of the SLB-IL61 and SLB-IL111 columns all but 8 congeners would be separated, including all 2,3,7,8-substituted PCDD/Fs. Two more congeners would be separated using a combination of SLB-IL76 and a liquid crystal (SB-Smectic) column, but in this case the 2,3,7,8-TeCDF would not be resolved. Three-column combinations would give even better separation: the DB-17/Smectic/SLB-IL76 and DB-225/Smectic/SLB-IL111 combinations would separate all but 1 of the 136 PCDD/F congeners. Unfortunately, the smectic column is no longer in production. If only commercially available columns are considered, combinations of SLB-IL61 and SLB-IL111 with DB-XLB, LC-50, or DB-225 offer the best performance, with 4, 4, and 3 unresolved congeners, respectively. Moreover, in each of these cases, one of the congeners in each unresolved pair is resolved on at least one of the other columns and so a reasonable estimate of the unresolved congeners' concentrations can be obtained by subtraction. The profiling of all 136 PCDD/Fs is thus greatly facilitated by using ionic liquid columns or combinations including such columns. However, there is room for improvement in the technical performance of the evaluated ionic liquid columns: their long-term retention time stability was poor and some highly chlorinated and sterically hindered congeners underwent dehalogenation during separation.

    (C) 2013 Elsevier B.V. All rights reserved.

  • 45.
    Edström, Lena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Samuelsson, Jörgen
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Fornstedt, Torgny
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Deformations of overloaded bands under pH-stable conditions in reversed phase chromatography2011In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1218, no 15, p. 1966-1973Article in journal (Refereed)
    Abstract [en]

    It has recently been demonstrated, using mathematical models, how peculiar overloaded band profiles of basic compounds are due to the local pH in the column when using low capacity buffers. In this study, overloaded peak shapes resulting after injection of carefully pH matched samples close to the pK(a) of the chosen solute are investigated primarily on two columns; one hybrid silica C18 column (Kromasil Eternity) and one purely polymeric column (PLRP-S), the latter lacking C18 ligands. It was found that distorted peaks of the basic test compound appear even though there is no difference in pH between the injected sample solution and the eluent; the previous explanation to why these effects occur is based on a pH mismatch. Thus, the unusual band shapes are not due to an initial pH difference. Furthermore, it was observed that the effect does not appear on polymeric columns without C18 ligands, but only on columns with C18 ligands, independently of the base matrix (silica, hybrid silica, polymeric).

  • 46. El-Beqqali, Aziza
    et al.
    Kussak, Anders
    Södertörn University, School of Life Sciences.
    Abdel-Rehim, Mohamed
    Fast and sensitive environmental analysis utilizing microextraction in packed syringe online with gas chromatography-mass spectrometry - Determination of polycyclic aromatic hydrocarbons in water2006In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1114, no 2, p. 234-238Article in journal (Refereed)
    Abstract [en]

    A new sensitive, selective, fast and accurate technique for online sample preparation was developed. Microextraction in a packed syringe (MEPS) is a new miniaturised, solid-phase extraction (SPE) technique that can be connected online to GC or LC without any modifications. In MEPS approximately 1 mg of the solid packing material is inserted into a syringe (100-250 ml) as a plug. Sample preparation takes place on the packed bed. The bed can be coated to provide selective and suitable sampling conditions. The new method is very promising. It is very easy to use, fully automated, of low cost and rapid in comparison with previously used methods. The determination of polycyclic hydrocarbons (PAHs) in water was performed using MEPS as sample preparation method online with gas chromatography and mass spectrometry (MEPS-GC-MS). The results from MEPS as sample preparation were compared with other techniques such as stir bar sorptive extraction (SBSE) and solid-phase microextraction (SPME). The method was validated and the standard curves were evaluated by the means of quadratic regression and weighted by inverse of the concentration: 1/x for the calibration range 5-1000 ng/L. The MEPS applied polymer (silica-C8) could be used more than 400 times before the syringe was discarded. The extraction recovery was about 70%. The results showed close correlation coefficients (R > 0.998) for all analytes in the calibration range studied. The accuracy of MEPS-GC-MS was between 90 and 113% and the inter-day precision (n = 3 days), expressed as the relative standard deviation (RSD%), was 8-16%. MEPS reduced the handling time by 30 and 100 times compared to SPME and SBSE, respectively.

  • 47.
    Elhamili, Anisa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Wetterhall, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Puerta, Angel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    Westerlund, Douglas
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Pharmaceutical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry.
    The effect of sample salt additives on capillary electrophoresis analysis of intact proteins using surface modified capillaries.2009In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 17, p. 3613-3620Article in journal (Refereed)
    Abstract [en]

    The effect of adding alkali salts to protein samples for capillary electrophoretic (CE) analysis of intact proteins was studied. A high degree of peak stacking, even for large proteins, was found to occur when alkali salts were added to the sample. The addition of salt to the protein sample promotes a strong improvement in the peak efficiency of individual proteins giving up to 2.1 x 10(6) apparent plates/m. The concentration of salt required in the sample to reach optimal peak efficiency show dependency on both the molecular weight and molar concentration of the protein. However, adding salt will, at a sufficiently high concentration, cause a mixture of proteins to co-migrate to one very sharp peak. The observed sample stacking effect was obtained with a number of different surface modified silica capillaries indicating a general phenomenon and not surface coating specific.

  • 48.
    Elmongy, Hatem
    et al.
    Stockholm Univ, Dept Environm Sci & Analyt Chem, SE-10691 Stockholm, Sweden.;Damanhour Univ, Fac Pharm, Dept Pharmaceut Anal, Damanhour 22511, Egypt..
    Ahmed, Hytham
    Damanhour Univ, Fac Pharm, Dept Pharmaceut Anal, Damanhour 22511, Egypt..
    Wahbi, Abdel-Aziz
    Univ Alexandria, Fac Pharm, Dept Pharmaceut Analyt Chem, Alexandria 21521, Egypt..
    Koyi, Hirsh
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, Centre for Research and Development, Gävleborg.
    Abdel-Rehim, Mohamed
    Stockholm Univ, Dept Environm Sci & Analyt Chem, SE-10691 Stockholm, Sweden..
    Online post-column solvent assisted and direct solvent-assisted electrospray ionization for chiral analysis of propranolol enantiomers in plasma samples2015In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1418, p. 110-118Article in journal (Refereed)
    Abstract [en]

    An Online post-column solvent-assisted ionization (OPSAI) method was developed for enhancing the ionization of the beta-blocker propranolol utilizing normal phase LC-MS/MS. Solvent-assisted electrospray ionization (SAESI) was studied by the introduction of the assistant solvents A: 0.5% Formic acid in Isopropanolol, B: 0.5% Formic acid in lsopropanolol-Water (1:1), and C: 0.5% Formic acid in water into the electrospray ionization chamber using a spray needle. Analyte molecules can be directly ionized by the aid of the assistant solvent spray. Both methods were applied to the chiral separation of propranolol enantiomers using normal phase analysis on cellulose-based chiral column. Interestingly, both methods are easy to handle and offer a wide range of assistant solvents that can be used in order to gain the optimum ionization of the analyte molecules. The both methods considerably improved the analyte signal and the peak area greatly increased. The propranolol average signal-to-noise (S/N) ratio was enhanced from 26 +/- 1 and 42 +/- 1 to 2341 +/- 61 and 1725 +/- 29 for R-propranolol and S-propranolol, respectively, when the post-column solvent method (OPSAI) was used with isopropanol-assistant solvent (A). While in case of solvent-assisted electrospray ionization method (SAESI) signal was enhanced from 26 +/- 1 and 42 +/- 1 to 2223 +/- 72 and 2155 +/- 58 for R-propranolol and S-propranolol, respectively, with water as an assistant solvent. The limit of detection was 10 ng/mL and the method was linear in the range 50-2000 ng/mL. The NPLC-MS method was applied for the determination of propranolol enantiomers in human plasma after microextraction by packed C18 sorbent.

  • 49.
    Elmongy, Hatem
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Damanhour University, Egypt.
    Ahmed, Hytham
    Wahbi, Abdel-Aziz
    Koyi, Hirsh
    Abdel-Rehim, Mohamed
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Online post-column solvent assisted and direct solvent-assisted electrospray ionization for chiral analysis of propranolol enantiomers in plasma samples2015In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1418, p. 110-118Article in journal (Refereed)
    Abstract [en]

    An Online post-column solvent-assisted ionization (OPSAI) method was developed for enhancing the ionization of the beta-blocker propranolol utilizing normal phase LC-MS/MS. Solvent-assisted electrospray ionization (SAESI) was studied by the introduction of the assistant solvents A: 0.5% Formic acid in Isopropanolol, B: 0.5% Formic acid in lsopropanolol-Water (1:1), and C: 0.5% Formic acid in water into the electrospray ionization chamber using a spray needle. Analyte molecules can be directly ionized by the aid of the assistant solvent spray. Both methods were applied to the chiral separation of propranolol enantiomers using normal phase analysis on cellulose-based chiral column. Interestingly, both methods are easy to handle and offer a wide range of assistant solvents that can be used in order to gain the optimum ionization of the analyte molecules. The both methods considerably improved the analyte signal and the peak area greatly increased. The propranolol average signal-to-noise (S/N) ratio was enhanced from 26 +/- 1 and 42 +/- 1 to 2341 +/- 61 and 1725 +/- 29 for R-propranolol and S-propranolol, respectively, when the post-column solvent method (OPSAI) was used with isopropanol-assistant solvent (A). While in case of solvent-assisted electrospray ionization method (SAESI) signal was enhanced from 26 +/- 1 and 42 +/- 1 to 2223 +/- 72 and 2155 +/- 58 for R-propranolol and S-propranolol, respectively, with water as an assistant solvent. The limit of detection was 10 ng/mL and the method was linear in the range 50-2000 ng/mL. The NPLC-MS method was applied for the determination of propranolol enantiomers in human plasma after microextraction by packed C18 sorbent.

  • 50.
    Elmsjö, Albert
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Science.
    Haglöf, Jakob
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Science.
    Engskog, Mikael K R
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Science.
    Erngren, Ida
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Science.
    Nestor, Marika
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science.
    Arvidsson, Torbjörn
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Science.
    Pettersson, Curt
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Analytical Science.
    Method selectivity evaluation using the co-feature ratio in LC/MS metabolomics: Comparison of HILIC stationary phase performance for the analysis of plasma, urine and cell extracts.2018In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1568, p. 49-56Article in journal (Refereed)
    Abstract [en]

    Evaluation of the chromatographic separation in metabolomics studies has primarily been done using preselected sets of standards or by counting the number of detected features. An alternative approach is to calculate each feature's co-feature ratio, which is a combined selectivity measurement for the separation (i.e. extent of co-elution) and the MS-signal (i.e. adduct formation and in-source fragmentation). The aim of this study was to demonstrate how the selectivity of different HILIC stationary phases can be evaluated using the co-feature ratio approach. The study was based on three sample types; plasma, urine and cell extracts. Samples were analyzed on an UHPLC-ESI-Q-ToF system using an amide, a bare silica and a sulfobetaine stationary phase. For each feature, a co-feature ratio was calculated and used for multivariate analysis of the selectivity differences between the three stationary phases. Unsupervised PCA models indicated that the co-feature ratios were highly dependent on type of stationary phase. For several metabolites a 15-30 fold difference in the co-feature ratio were observed between the stationary phases. Observed selectivity differences related primarily to the retention patterns of unwanted matrix components such as inorganic salts (detected as salt clusters), glycerophospholipids, and polyethylene glycols. These matrix components affected the signal intensity of co-eluting metabolites by interfering with the ionization efficiency and/or their adduct formation. Furthermore, the retention pattern of these matrix components had huge influence on the number of detected features. The co-feature ratio approach has successfully been applied for evaluation of the selectivity performance of three HILIC stationary phases. The co-feature ratio could therefore be used in metabolomics for developing selective methods fit for their purpose, thereby avoiding generic analytical approaches, which are often biased, as type and amount of interfering matrix components are metabolome dependent.

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