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  • 1. Araujo, Pedro
    et al.
    Tilahun, Ephrem
    Zeng, Yingxu
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Section of Sustainable Health.
    A novel strategy for discriminating marine oils by using the positional distribution (sn-1, sn-2, sn-3) of omega-3 polyunsaturated fatty acids in triacylglycerols2018In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 182, p. 32-37Article in journal (Refereed)
    Abstract [en]

    A novel strategy for discriminating genuine and adulterated marine oils is proposed. The strategy consists of i) determining the stereospecific distribution (sn-1, sn-2 and sn-3) of omega 3 polyunsaturated fatty acids (omega-3 PUFA) on the backbone of triacylglycerols by using liquid chromatography tandem mass spectrometry; ii) transforming the qualitative stereospecific information into quantitative data by means of a novel strategy; iii) analyzing the transformed data by principal component analysis. The proposed strategy was tested on pure oils (seal, salmon, cod liver, sandeel, blue whiting, herring), a mixture of blue whiting, herring, sandeel and Norway pout and some intentionally adulterated oils. In addition, some published krill oil data were analyzed to confirm the reliability of the new approach.

  • 2. De Brabandere, Heidi
    et al.
    Danielsson, Rolf
    Sjoberg, Per J. R.
    Ahlgren, Joakim
    Rydin, Emil
    Waldeback, Monica
    Sediment extraction and clean-up for organic phosphorus analysis by electrospray ionization tandem mass spectrometry2008In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 74, no 5, p. 1175-1183Article in journal (Refereed)
    Abstract [en]

    A method to prepare NaOH sediment extracts for organic P compound analysis with electrospray ionization tandem mass spectrometry (ESI-MS-MS) was developed on natural samples. Ion exchange, rotary evaporation and mass cut-off filtering proved to be suitable for sample preparation. Samples were analyzed with ESI-MS-MS, and reproducibility and repeatability of the method was calculated. In addition, P-31-nuclear magnetic resonance Spectroscopy (P-31 NMR)was used to measure recovery of different P compound groups such as orthophosphate (Ortho-P), orthophosphate monoesters (Monoester-P), orthophosphate diesters (Diester-P) and pyrophosphates (Pyro-P). The developed sample preparation method resulted in an easy-to-spray liquid for the ESI-MS-MS instrumentation. The overall P recovery was 65% and P-31 NMR showed that Diester-P, possibly in the form of DNA, was apparently lost through the filtering step most likely due to their size. Variances in the total intensities of the MS scans (relative standard deviation (R.S.D.) 35-54%) were for about 50% due to repeated MS runs. Covariances of the peaks in the MS spectra were calculated to be for about 30% due to the sample preparation procedure. Finally, with the ESI-MS-MS approach, 11 peaks in the mass spectra were found likely to represent phosphate containing compounds. (c) 2007 Elsevier B.V. All rights reserved.

  • 3.
    Ghorbanzad‘e, Mehdi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fatemi, Mohammad H
    Karimpour, Masoumeh
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Andersson, Patrik L
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Quantitative and qualitative prediction of corneal permeability for drug-like compounds2011In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 85, no 5, p. 2686-2694Article in journal (Refereed)
    Abstract [en]

    A set of 69 drug-like compounds with corneal permeability was studied using quantitative and qualitative modeling techniques. Multiple linear regression (MLR) and multilayer perceptron neural network (MLP-NN) were used to develop quantitative relationships between the corneal permeability and seven molecular descriptors selected by stepwise MLR and sensitivity analysis methods. In order to evaluate the models, a leave many out cross-validation test was performed, which produced the statistic Q2 = 0.584 and SPRESS = 0.378 for MLR and Q2 = 0.774 and SPRESS = 0.087 for MLP-NN. The obtained results revealed the suitability of MLP-NN for the prediction of corneal permeability. The contribution of each descriptor to MLP-NN model was evaluated. It indicated the importance of the molecular volume and weight. The pattern recognition methods principal component analysis (PCA) and hierarchical clustering analysis (HCA) have been employed in order to investigate the possible qualitative relationships between the molecular descriptors and the corneal permeability. The PCA and HCA results showed that, the data set contains two groups. Then, the same descriptors used in quantitative modeling were considered as inputs of counter propagation neural network (CPNN) to classify the compounds into low permeable (LP) and very low permeable (VLP) categories in supervised manner. The overall classification non error rate was 95.7% and 95.4% for the training and prediction test sets, respectively. The results revealed the ability of CPNN to correctly recognize the compounds belonging to the categories. The proposed models can be successfully used to predict the corneal permeability values and to classify the compounds into LP and VLP ones.

    Highlights

    ► Linear and nonlinear prediction of corneal permeability using molecular descriptors. ► MLP-NN model was found to be more successful than MLR equation. ► Molecular volume and molecular weight were identified as the most important descriptors. ► Categorizing drugs in two low permeable and very low permeable compounds groups. ► CPNN model can correctly recognize objects belonging to the groups.

  • 4.
    Grabic, Roman
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fick, Jerker
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lindberg, Richard H
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fedeorova, Ganna
    Tysklind, Mats
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Multi-residue method for trace level determination of pharmaceuticals in environmental samples using liquid chromatography coupled to triple quadrupole mass spectrometry2012In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 100, p. 183-195Article in journal (Refereed)
    Abstract [en]

    A multi-residue method for the simultaneous determination of more than 90 pharmaceuticals in water samples was developed and validated. The developed method utilizes a single liquid chromatography–tandem mass spectrometry (LC–MS/MS) run after sample enrichment using solid-phase extraction (SPE). The pharmaceuticals included in this method were chosen based on their potency (effect/concentration ratio) and potential to bioaccumulate in fish. Because the selection was based on ecotoxicological criteria and not on ease of detection, the pharmaceuticals have a wide range of physico-chemical properties and represent twenty-seven distinct classes. No method for surface, waste water or similar matrices was previously described for 52 of the 100 target analytes. Four chromatographic columns were tested to optimize the separation prior to detection by mass spectrometry (MS). The resulting method utilizes a Hypersil Gold aQ column. Three different water matrices were tested during method validation: Milli-Q water, surface water (river water from the Umea River) and effluent from the Umea waste water treatment plant (WWTP). Four of the selected pharmaceuticals exhibited poor method efficiency in all matrices. Amiodarone, Dihydroergotamine, Perphenazine and Terbutalin were omitted from the final analytical method (). In addition, five compounds were excluded from the method for surface water (Atorvastatin, Chloropromazin, Dipyridamol, Furosemid and Ranitidin) and three other pharmaceuticals (Glibenclamid, Glimepirid and Meclozine) from waste water method respectively. Absolute recoveries were above 70% for Milli-Q water, surface water, and sewage effluent for most pharmaceuticals. The limits of quantification (LOQs) ranged from 0.05 to 50 ng L−1 (median 5 ng L−1). The use of matrix-matched standards led to the elimination of ionization enhancement or suppression. The recoveries of the method for real matrices were in the range of 23% to 134% for surface water (only three compounds were outside of the range of 40–130%) and in the range of 47% to 162% for waste water (five compounds were outside of the range of 40–130% at lower validated concentration).

  • 5.
    Larsson, William
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Cedergren, Anders
    Umeå University, Faculty of Science and Technology, Chemistry.
    Coulometric Karl Fischer titration of trace water in diaphragm-free cells2005In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 65, no 5, p. 1349-54Article in journal (Refereed)
    Abstract [en]

    Factors influencing the accuracy and precision for diaphragm-free Karl Fischer coulometric determinations of low mu g-amounts of water have been studied using the Metrohm 756 (pulsed current) coulometer and eight different types of commercial coulometric reagents and some modifications of these. As in the case of diaphragm-free coulometric titration of large amounts of water, the positive errors, due to the formation of oxidizable reduction products (of sulfur dioxide) in the cathode reaction (besides hydrogen), were found to be minimized by the use of highest possible pulse current (in the range 100-400 mA) in combination with the fastest possible titration rate. Most accurate (102-103%) and precise results (typical relative standard deviation 1.8%) were obtained for reagents containing very large concentrations of imidazole in combination with the presence of modifiers like hexanol, chloroform and propylene glycol (i.e. the HYDRA-POINT reagents). Similar results were obtained when this type of reagent was mixed 60/40 with xylene according to the ASTM recommendation for water determinations in petroleum products like crude and lubricating oils. Addition of decanol to this type of reagent mixture was found to reduce the influence from the oxidative reduction products significantly. A reduction of the error from 3.6% relative to 1.6% was achieved by addition of 9% (v/v) of decanol to a 60/40 reagent mixture of HYDRA-POINT Coulometric Gen (containing hexanol as modifier) and xylene. For larger concentrations of decanol the pulse current had to be lowered to 100 mA and this might explain why no further improvement was observed. An additional attempt to minimize the interference by lowering the concentration of sulfur dioxide in the reagents gave no significant effect. However. by means of a home-built computer-controlled coulometric instrumentation based on continuous instead of pulsed current (including a large cathodic current density) it was possible to achieve recovery rates close to 100% for the best reagents investigated. The reason for this improvement is discussed.

  • 6.
    Larsson, William
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Cedergren, Anders
    Investigation of Amine-Buffered Amide Reagents for Coulometric Karl Fischer Titration2009In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 78, no 4-5, p. 1452-1457Article in journal (Refereed)
    Abstract [en]

    Formamide (FA), N-methylformamide (NMF), and dimethylformamide (DMF),were evaluated as solvents for coulometric Karl Fischer (KF) reagents in combination with several amine bases. Except for the effect of the iodine species (iodine or triiodide), the pH of the reagent and the position of the sulfur dioxide/ hydrogen sulfite equilibrium were found to be the main factors explaining the large difference in the observed reaction rates betweenwater and the KF reagent in these solvents. Acid–base titrations showed that hydrogen sulfite is the main sulfur reactant in these media. The results will be of great importance in finding suitable combinations of base and solvent with respect to stoichiometry, side reactions caused by active carbonyl compounds, and reagent stability.

  • 7.
    Larsson, William
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Panitz, Jan-Christoph
    Cedergren, Anders
    Umeå University, Faculty of Science and Technology, Chemistry.
    Interference-free coulometric titration of water in lithium bis(oxalato)borate using Karl Fischer reagents based on N-methylformamide2006In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 69, no 1, p. 276-280Article in journal (Refereed)
    Abstract [en]

    A non-alcoholic coulometric reagent based on N-methylformamide (NMF) was shown to eliminate the severe interference effect caused by the alcohol component of the conventional Karl Fischer (KF) reagent on the battery electrolyte lithium bis(oxalato)borate (LiBOB). For sample amounts up to 240 μg of water, the stoichiometry of the KF reaction deviated only slightly from the ideal 1:1 ratio for the best reagent composition. Both solid and dissolved (in acetonitrile, tetrahydrofuran (THF), and ethylene carbonate/ethyl methyl carbonate) LiBOB were titrated successfully using a Metrohm 756 KF Coulometer with a diaphragm cell. The detection limit was estimated to be 0.5–1 μg of water using 100 ml of reagent in this system.

  • 8.
    Lindberg, Richard H.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Fedorova, Ganna
    Umeå University, Faculty of Science and Technology, Department of Chemistry. University of South Bohemia in Ceske Budejovice, Faculty of Fisheries and Protection of Waters, South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses, Zatisi 728/II, 389 25 Vodnany, Czech Republic.
    Blum, Kristin M.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Pulit-Prociak, Jolanta
    Gillman, Anna
    Järhult, Josef
    Appelblad, Patrik
    Söderström, Hanna
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Online solid phase extraction liquid chromatography using bonded zwitterionic stationary phases and tandem mass spectrometry for rapid environmental trace analysis of highly polar hydrophilic compounds – Application for the antiviral drug Zanamivir2015In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 141, p. 164-169Article in journal (Refereed)
    Abstract [en]

    Abstract Zanamivir (Za) is a highly polar and hydrophilic antiviral drug used for the treatment of influenza A viruses. Za has been detected in rivers of Japan and it's environmental occurrence has the risk of inducing antiviral resistant avian influenza viruses. In this study, a rapid automated online solid phase extraction liquid chromatography method using bonded zwitterionic stationary phases and tandem mass spectrometry (SPE/LC–MS/MS) for trace analysis of Za was developed. Furthermore, an internal standard (IS) calibration method capable of quantifying Za in Milli-Q, surface water, sewage effluent and sewage influent was evaluated. Optimum pre-extraction sample composition was found to be 95/5 v/v acetonitrile/water sample and 1% formic acid. The developed method showed acceptable linearities (r2≥0.994), filtration recovery (≥91%), and intra-day precisions (RSD≤16%), and acceptable and environmentally relevant LOQs (≤20 ng L−1). Storage tests showed no significant losses of Za during 20 days and +4/−20 °C (≤12%) with the exception of influent samples, which should be kept at −20 °C to avoid significant Za losses. The applicability of the method was demonstrated in a study on phototransformation of Za in unfiltered and filtered surface water during 28 days of artificial UV irradiation exposure. No significant (≤12%) phototransformation was found in surface water after 28 days suggesting a relatively high photostability of Za and that Za should be of environmental concern.

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