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  • 1.
    Bexell, Ulf
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Engkvist, Josefin
    Chalmers University of Technology, Göteborg, Sweden.
    Malmberg, Per
    Chalmers University of Technology, Göteborg, Sweden.
    Comparing 69Ga+ and C60+ for ToF-SIMS sputter depth profiling in a Cr2O3 formed during oxidation of a Ce coated FeCr steel substrate2012Conference paper (Other academic)
  • 2.
    Blessborn, Daniel
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Römsing, Susanne
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    A semi-quantitative screening method to identify some of the most commonly used antimalarial drugs2009In: Tropical medicine & international health, ISSN 1360-2276, E-ISSN 1365-3156, Vol. 14, p. 130-130Article in journal (Other academic)
  • 3.
    Blessborn, Daniel
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Römsing, Susanne
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Annerberg, Anna
    Sundquist, Daniel
    Björkman, Anders
    Lindegårdh, Niklas
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Development and validation of an automated solid-phase extraction and liquid chromatographic method for determination of lumefantrine in capillary blood on sampling paper.2007In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 45, no 2, p. 282-287Article in journal (Refereed)
    Abstract [en]

    A bioanalytical method for the determination of lumefantrine in 100 µl blood applied onto sampling paper, by solid-phase extraction and liquid chromatography, has been developed and validated. Whatman 31 ET Chr sampling paper was pre-treated with 0.75 M tartaric acid before sampling capillary blood to enable a high recovery of lumefantrine. Lumefantrine was extracted from the sampling paper, then further purified using solid-phase extraction and finally quantified with HPLC. The between-day variation was below 10% over the range 0.4–25 µM. The lower limit of quantification was 0.25 µM in 100 µl capillary blood. No decrease in lumefantrine concentration in dried blood spot is seen after 4 months storage at 22 °C. The method was also evaluated in field samples from patients in Tanzania after treatment with lumefantrine/artemether. Lumefantrine could be estimated accurately enough to assess bioavailability and treatment compliance on day 7 (i.e. 4 days after the last dose) after a standard regimen with the lumefantrine/artemether combination.

  • 4.
    Blessborn, Daniel
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Römsing, Susanne
    Dalarna University, School of Education, Health and Social Studies, Chemistry.
    Bergqvist, Yngve
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Lindegardh, Niklas
    Assay for screening for six antimalarial drugs and one metabolite using dried blood spot sampling, sequential extraction and ion-trap detection2010In: Bioanalysis, ISSN 1757-6180, E-ISSN 1757-6199, Vol. 2, no 11, p. 1839-1847Article in journal (Refereed)
    Abstract [en]

    Background: More parasites are becoming resistant to antimalarial drugs, and in many areas a change in first-line drug treatment is necessary. The aim of the developed assay is to help determine drug use in these areas and also to be a complement to interviewing patients, which will increase reliability of surveys.

    Results: This assay detects quinine, mefloquine, sulfadoxine, pyrimethamine, lumefantrine, chloroquine and its metabolite desethylchloroquine in a 100-mu l dried blood spot. Most of the drugs also have long half-lives that make them detectable at least 7 days after administration. The drugs are extracted from the dried blood spot with sequential extraction (due to the big differences in physicochemical properties), solid-phase extraction is used as sample clean-up and separation is performed with gradient-LC with MS ion-trap detection.

    Conclusion: Detection limits (S/N > 5:1) at 50 ng/ml or better were achieved for all drugs except lumefantrine (200 ng/ml), and thus can be used to determine patient compliance. A major advantage of using the ion-trap MS it that it will be possible to go back into the data and look for other drugs as needed.

  • 5.
    Engkvist, Josefin
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science. Chalmers University of Technology, Göteborg, Sweden.
    Israelsson, Niklas
    Chalmers University of Technology, Göteborg, Sweden.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    The initial effect of KCl deposit on alumina scales characterized by ToF-SIMS and AES2013In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 45, no 1, p. 445-448Article in journal (Refereed)
    Abstract [en]

    A FeCrAl alloy was preoxidized to form a protective alumina scale, and the effect of KCl deposits on the alumina scale was investigated while exposed during 1 and 24 h at 600 °C. However, impurity concentrations in the alumina scale change the ion conductivity and hence affect its protective properties. Therefore, Auger electron spectroscopy and time-of-flight secondary ion mass spectrometry were used to characterize the alumina scales and detect traces of K and Cl. The results showed that K and Cl existed as large sharp-edged crystals surrounded by a dendritic network after 1 h. However, after 24 h, those were dissolved, and K together with Cl was detected only in the outer layer of the duplex alumina scale, which was formed during preoxidation.

  • 6. Hultquist, Gunnar
    et al.
    Graham, M. J.
    Kodra, O.
    Moisa, R.
    Liu, R.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Smialek, J. L.
    Corrosion of copper in distilled water without molecular oxygen and the detection of produced hydrogen2013Report (Other academic)
    Abstract [en]

    This paper reports on hydrogen pressures measured during the longterm immersion (~19 000 hours) of copper in oxygen-free distilled water. Hydrogen gas evolution is from copper corrosion and similar pressures (in the mbar range) are measured for copper contained in either a 316 stainless steel or titanium system. Copper corrosion products have been examined ex-situ by SEM and characterized by Xray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). XPS strongly indicates a corrosion product containing both hydroxide and oxide. SIMS shows that oxygen is mainly present in the outer 0.3 um surface region and that hydrogen penetrates to depths in the substrate well below the corrosion product.

  • 7. Jansson-Löfmark, Rasmus
    et al.
    Römsing, Susanne
    Dalarna University, School of Education, Health and Social Studies, Chemistry.
    Albers, E
    Ashton, M
    Determination of eflornithine enantiomers in plasma by precolumn derivatization with o-phthalaldehyde-N-acetyl-L-cysteine and liquid chromatography with UV detection2010In: BMC Biomedical chromotography, ISSN 0269-3879, E-ISSN 1099-0801, Vol. 24, no 7, p. 768-773Article in journal (Refereed)
    Abstract [en]

    A bioanalytical method for indirect determination of eflornithine enantiomers in 75?µL human plasma has been developed and validated. l- and d-eflornithine were derivatized with o-phthalaldehyde and N-acetyl-L-cysteine to generate diastereomers which were separated on two serially connected Chromolith Performance columns (RP-18e 100 × 4.6?mm i.d.) by a isocratic flow followed by a gradient flow for elution of endogenous compounds. The diastereomers were detected with UV (340?nm). The between-day precisions for L- and D-eflornithine in plasma were 8.4 and 2.3% at 3?µm, 4.0 and 5.1% at 400?µm, and 2.0 and 3.7% at 1000?µm. The lower limit of quantification was determined to be 1.5?µm, at which precision was 14.9 and 9.9% for L- and D-eflornithine, respectively

  • 8. Kofoed, P.E.
    et al.
    Ursing, J.
    Poulsen, A.
    Rodrigues, A.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Aaby, P.
    Rombo, L.
    Different doses of amodiaquine and chloroquine for treatment of uncomplicated malaria in children in Guinea-Bissau: implications for future treatment recommendations2007In: Transactions of the Royal Society of Tropical Medicine and Hygiene, ISSN 0035-9203, E-ISSN 1878-3503, Vol. 101, no 3, p. 231-238Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to compare different doses of chloroquine (CQ) and amodiaquine (AQ) for the treatment of falciparum malaria in children. Children with Plasmodium falciparum monoinfection were allocated by block randomisation to treatment with CQ 50/kg mg or 25 mg/kg or AQ 15 mg/kg or 30 mg/kg. The main outcomes were the cumulative adequate clinical and parasitological response (ACPR) rates and the number of true recrudescences as determined by PCR. A total of 729 children were included. In an evaluability analysis, the PCR-uncorrected cumulative ACPR rates on Day 28 for the treatment groups CQ 50/kg mg or 25 mg/kg and AQ 15 mg/kg or 30 mg/kg were 90%, 76%, 92% and 94%, respectively; the PCR-adjusted ACPR rates on Day 28 were 92%, 80%, 94% and 94%, respectively. No differences in adverse effects were observed. AQ has a high cure rate given as 30 mg/kg and 15 mg/kg, although it is not superior to treatment with CQ 50 mg/kg. However, 25 mg/kg of CQ is less efficient. As an interim option, Guinea-Bissau could change the recommended first-line treatment of uncomplicated malaria to CQ 50 mg/kg, reserving AQ as a partner drug for a future combination therapy.

  • 9. Lindegårdh, Niklas
    et al.
    Annerberg, A.
    Blessborn, Daniel
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Day, N.
    White, N.J.
    Development and validation of a bioanalytical method using automated solid-phase extraction and LC-UV for the simultaneous determination of lumefantrine and its desbutyl metabolite in plasma2005In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 37, no 5, p. 1081-1088Article in journal (Refereed)
    Abstract [en]

    A bioanalytical method for the determination of lumefantrine (LF) and its metabolite desbutyl-lumefantrine (DLF) in plasma by solid-phase extraction (SPE) and liquid chromatography has been developed. Plasma proteins were precipitated with acetonitrile: acetic acid (99:1, v/v) containing a DLF analogue internal standard before being loaded onto a octylsilica (3 M Empore) SPE column. Two different DLF analogues were evaluated as internal standards. The compounds were analysed by liquid chromatography UV detection on a SB-CN (250 mm x 4.6 mm) column with a mobile phase containing acetonitrile-sodium phosphate buffer pH (2.0; 0.1 M) (55:45, v/v) and sodium perchlorate 0.05 M. Different SPE columns were evaluated during method development to optimise reproducibility and recovery for LF, DLF and the two different DLF analogues. The within-day precisions for LF were 6.6 and 2.1% at 0.042 and 8.02 μ g/mL, respectively, and for DLF 4.5 and 1.5% at 0.039 and 0.777 μ g/mL, respectively. The between-day precisions for LF were 12.0 and 2.9% at 0.042 and 8.02 μ g/mL, respectively, while for DLF 0.7 and 1.2% at 0.039 and 0.777 μ g/mL, respectively. The limit of quantification was 0.024 and 0.021 μ g/mL for LF and DLF, respectively. Different amounts of lipids in plasma did not affect the absolute recovery of LF or DLF.

  • 10. Lindegårdh, Niklas
    et al.
    Blessborn, Daniel
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Simultaneous quantification of the highly lipophilic atovaquone and the hydrophilic strong basic proguanil and its metabolites, using a new mixed-mode SPE approach and Steep-Gradient LC2005In: Journal of Chromatographic Science, ISSN 0021-9665, E-ISSN 1945-239X, Vol. 43, no 5, p. 259-266Article in journal (Refereed)
    Abstract [en]

    A bioanalytical method is described for the simultaneous quantitative analysis of the highly lipophilic atovaquone and the strong basic proguanil with metabolites in plasma. The drugs are extracted from protein precipitated plasma samples on a novel mixed-mode solid-phase extraction (SPE) column containing carboxypropyl and octyl silica as functional groups. The analytes are further separated and quantitated using a steep-gradient liquid chromatograhic method on a Zorbax SB-CN column with UV detection at 245 nm. Two different internal standards (IS) are used in the method to compensate for both types of analytes. A structurally similar IS to atovaquone is added with acetonitrile to precipitate proteins from plasma. A structurally similar IS to proguanil and its metabolites is added with phosphate buffer before samples are loaded onto the SPE columns. A single elution step is sufficient to elute all analytes. The method is validated according to published guidelines and shows excellent performance. The within-day precisions, expressed as relative standard deviation, are lower than 5% for all analytes at three tested concentrations within the calibration range. The between-day precisions are lower than 13% for all analytes at the same tested concentrations. The limit of quantitation is 25nM for the basic substances and 50nM for atovaquone. Several considerations regarding development and optimization of a method for determination of analytes with such a difference in physiochemical properties are discussed.

  • 11.
    Lindkvist, Jenny
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Malm, Mikaela
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Straightforward and rapid determination of sulfadoxine and sulfamethoxazole in capillary blood on sampling paper with liquid chromatography and UV detection2009In: Transactions of the Royal Society of Tropical Medicine and Hygiene, ISSN 0035-9203, E-ISSN 1878-3503, Vol. 103, no 4, p. 371-376Article in journal (Refereed)
    Abstract [en]

    A method for the determination of sulfadoxine and sulfamethoxazole in capillary blood on sampling paper has been developed and validated. The method is straightforward with minimal sample preparation, and is suitable for rural settings. Separation of sulfadoxine, sulfamethoxazole and internal standard was performed using a Purospher STAR RP-18 endcapped LC column (150 x 4.6 mm) with a mobile phase consisting of acetonitrile: sodium acetate buffer pH 5.2, 1=0.1 (1:2, v/v). For sulfadoxine, the within-day precision was 5.3% at 15 mu mol/l and 3.7% at 600 mu mol/l, while for sulfamethoxazole it was 5.7% at 15 mu mol/l and 3.8% at 600 mu mol/l. The tower limit of quantification was determined to 5 mu mol/l and precision was 5.5% and 5.0% for sulfadoxine and sulfamethoxazole, respectively.

  • 12.
    Malm, Mikaela
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Determination of eflornithine enantiomers in plasma, by solid-phase extraction and liquid chromatography with evaporative light-scattering detection2007In: Journal of Chromatography B: Biomedical Sciences and Applications, ISSN 1387-2273, E-ISSN 1878-5603, Vol. 846, no 1-2, p. 98-104Article in journal (Refereed)
    Abstract [en]

    A bioanalytical method for determination of eflomithine (DEMO) in 1000 p,L human plasma has been developed and validated. DFMO and the internal standard (IS) were analysed by liquid chromatography with evaporative light-scattering detection (ELSD). Separation was performed on a Chirobiotic TAG (250 mm x 4.6 mm) column with ethanol (99.5%):0.01 mol/L acetic acid-triethylamine buffer at the rate of 25:75% (v/v) with flow rate of 1.0 mL/min. For D-DFMO in plasma the inter-assay precision was 6.5% at 75 p,mol/L, 6.6% at 375 mu mol/L and 5.8% at 750 mu mol/L. For L-DFMO in plasma the inter-assay precision was 10.4% at 75 mu mol/L, 6.5% at 375 mu mol/L and 5.0% at 750 lumol/L. The lower limit of quantification (LLOQ) was determined to 25 mu mol/L where the precision was 4.3% and 5.7%, respectively.

  • 13.
    Malm, Mikaela
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Römsing, Susanne
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Obua, Celestino
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Determination of lamivudine, zidovudine and nevirapine, in capillary blood sampled on filter paper, by liquid chromatography2009In: Journal of Chromatographic Science, ISSN 0021-9665, E-ISSN 1945-239X, Vol. 47, no 10, p. 855-862Article in journal (Refereed)
    Abstract [en]

    A bioanalytical method for determination of lamivudine (3TC), zidovudine (AZT), and nevirapine (NVP) in 100 μL capillary blood applied onto sampling paper has been developed and validated. The antiretroviral drugs (ARV) were analyzed by reversed phase gradient liquid chromatography with UV detection. Separation was performed on a Zorbax SB C8 (250 × 4.6 mm) column with a twostep gradient: (i) methanol.0.05 mol/L acetic acid-sodium acetate buffer (pH 3.95, 15:85 v/v) and (ii) methanol.0.05 mol/L acetic acid-sodium acetate buffer (pH 3.95, 50:50 v/v) with a flow rate of 1.0 mL/min. UV detection was performed at 260 nm. Total assay precisions were 6.3, 4.7, and 4.9% for 3TC at 0.34, 0.69, and 3.9 μg/mL, and 5.1, 5.5, and 3.2% for AZT at 0.40, 0.80, and 4.5 μg/mL. For NVP, total assay precisions were 5.2, 8.3, and 3.5% at 2.6, 4.5, and 8.8 μg/mL. Lower limit of quantifications (LLOQ) were 0.11 and 0.13 μg/mL for 3TC and AZT where the precisions were 2.0% for both the analytes. For NVP, LLOQ was 1.3 μg/mL where precision was 2.6%. Concentrations were determined for 10 h for two subjects receiving standard twice daily antiretroviral therapy containing 3TC, AZT, and NVP. Maximum 3TC concentrations were 2.5 and 2.8 μg/mL for subject 1 and 2, respectively. For AZT, maximum concentrations were 1.8 and 1.1 μg/mL while being 15 and 9.6 μg/mL for NVP. Pre-dose trough concentration of NVP was 11 μg/mL for subject 1 and 9.6 μg/mL for subject 2.

  • 14.
    Rhenlund, David
    et al.
    Uppsala Universitet.
    Lindgren, Fredrik
    Uppsala Universitet.
    Böhme, Solveig
    Uppsala Universitet.
    Nordh, Tim
    Uppsala Universitet.
    Zou, Yiming
    Uppsala Universitet.
    Pettersson, Jean
    Uppsala Universitet.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Boman, Mats
    Uppsala Universitet.
    Edström, Kristina
    Uppsala Universitet.
    Leif, Nyholm
    Uppsala Universitet.
    Improved Cycling Stability of Conversion and Alloying Anodes through the use of Nanomaterials2016Conference paper (Refereed)
  • 15.
    Zhou, Nian
    Dalarna University, School of Technology and Business Studies, Materials Technology. KTH.
    Influence of grinding operations on surface integrity and chloride induced stress corrosion cracking of stainless steels2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Stainless steels were developed in the early 20th century and are used where both the mechanical properties of steels and corrosion resistance are required. There is continuous research to allow stainless steel components to be produced in a more economical way and be used in more harsh environments. A necessary component in this effort is to correlate the service performance with the production processes.

    The central theme of this thesis is the mechanical grinding process.  This is commonly used for producing stainless steel components, and results in varied surface properties that will strongly affect their service life. The influence of grinding parameters including abrasive grit size, machine power and grinding lubricant were studied for 304L austenitic stainless steel (Paper II) and 2304 duplex stainless steel (Paper I). Surface integrity was proved to vary significantly with different grinding parameters. Abrasive grit size was found to have the largest influence. Surface defects (deep grooves, smearing, adhesive/cold welding chips and indentations), a highly deformed surface layer up to a few microns in thickness and the generation of high level tensile residual stresses in the surface layer along the grinding direction were observed as the main types of damage when grinding stainless steels. A large degree of residual stress anisotropy is interpreted as being due to mechanical effects dominating over thermal effects.

    The effect of grinding on stress corrosion cracking behaviour of 304L austenitic stainless steel in a chloride environment was also investigated (Paper III). Depending on the surface conditions, the actual loading by four-point bend was found to deviate from the calculated value using the formula according to ASTM G39 by different amounts. Grinding-induced surface tensile residual stress was suggested as the main factor to cause micro-cracks initiation on the ground surfaces. Grinding along the loading direction was proved to increase the susceptibility to chloride-induced SCC, while grinding perpendicular to the loading direction improved SCC resistance.

    The knowledge obtained from this work can provide a reference for choosing appropriate grinding parameters when fabricating stainless steel components; and can also be used to help understanding the failure mechanism of ground stainless steel components during service.

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