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  • 1. Annerberg, A
    et al.
    Lindegårdh, Niklas
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Blessborn, Daniel
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    White, N
    A bioanalytical method using automated solid-phase extraction and LC-UV for the simultaneous determination of lumefantrine and its desbutyl metabolite in plasma2004In: PBA, Florens, Italien, 2004Conference paper (Other academic)
  • 2.
    Bergqvist, Yngve
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Lindegårdh, N
    Determinations of Antimalarial Drug Levels in Body Fluids2007In: Travelers´ Malaria / [ed] Schlagenhauf, Patricia, London: BC Decker , 2007, p. 135-170Chapter in book (Other academic)
  • 3. Blessborn, D
    et al.
    Lindegårdh, Niklas
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Ericsson, Ö
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Determination of pyronaridine in whole blood by automated solid-phase extraction and high-performance liquid chromatography2003In: Therapeutic Drug Monitoring, ISSN 0163-4356, E-ISSN 1536-3694, no 25, p. 264-270Article in journal (Refereed)
  • 4.
    Blessborn, Daniel
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Development of Analytical Methods for Measurement of Drugs against Malaria in Plasma and Whole Blood2006Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The aim of this thesis was to develop analytical methods for measuring drugs in blood and/or plasma. Solid phase extraction was used for the enrichment and purification of the drugs from the sample matrix. Automatic extraction procedures using a solid phase extraction robot to reduce the workload of the analyst and to minimize variations in the extraction procedure were developed. To determine sample concentrations, liquid chromatography was used together with UV absorbance detection through out this work. Determination of Pyronaridine in whole blood utilised a weak cation exchanger to extract Pyronaridine from blood. From the beginning there were problems in separating Pyronaridine from the internal standard but by adding sodium perclorate as an ion-pairing agent, good separation was achieved. For the simultaneous quantification of the highly lipophilic Atovaquone and the strong basic drug Proguanil with metabolites, a novel mixed mode solid phase extraction column was used. It combines the properties of a carboxylic acid (CBA) column and a non-polar octyl-silica (C8) column to extract the compounds from plasma. Their different physiochemical properties also required a gradient separation on the liquid chromatography system. Stability is an important factor when developing new methods. A new approach was used to evaluate the stability of Amodiaquine in blood and plasma. This included the use of a stability marker, in this case Chloroquine, a stable compound which was added together with Amodiaquine when preparing the stability samples. When using the ratio of Amodiaquine and the stability marker, between-run variations and variations associated with the preparation of new stock solutions and calibration standards were eliminated.

  • 5.
    Blessborn, Daniel
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Lundrell, R
    Lindegårdh, N
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Determination of lumefantrine in plasma after sampling onto sampling paper by solid-phase extraction and liquid chromatography with UV-detection2005In: International Congress for Tropical medicine and Malaria, Marseille, 2005Conference paper (Refereed)
  • 6.
    Blessborn, Daniel
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Neamin, G.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Lindegårdh, N.
    A new approach to evaluate stability of amodiaquine and its metabolite in blood and plasma2006In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 41, no 1, p. 207-212Article in journal (Refereed)
    Abstract [en]

    A stability study for amodiaquine (AQ) and desethylamodiaquine (AQm) in whole blood and plasma is reported. AQ, AQm and chloroquine (CQ) were simultaneously analysed and the ratios AQ/CQ and AQm/CQ were used to ensure correct interpretation of the stability results. CQ was stable in whole blood and plasma at all tested temperatures enabling it to be a stability marker in stability studies. Simultaneous analysis of compounds, of which at least one is already known to be stable, permits a within sample ratio to be used as a stability indicator, The new approach significantly reduced bias when compared to the traditional approach. AQ and AQm were stable in plasma at -86 degrees C and -20 degrees C for 35 days, at 4 degrees C for 14 days and at 22 degrees C for 1 day. AQ and AQm were stable in blood at -86 degrees C and 4 degrees C for 35 days, at -20 degrees C and 22 degrees C for 7 days and at 37 degrees C for 1 day.

  • 7.
    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)
  • 8.
    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.
    Determination of Lumefantrine after Capillary Sampling onto Sampling Paper2007In: The Royal Society of Tropical Medicine and Hygiene, London, 2007Conference paper (Refereed)
    Abstract [en]

    The antimalarial lumefantrine was first synthesised and registered in China and is now commercially available as a coformulated product together with artemether (Coartem®/Riamet®). This combination is well tolerated and has proven highly efficacious for treatment of uncomplicated falciparum malaria. Lumefantrine is highly lipophilic with an extensive protein binding (99.9%). The day 7 plasma lumefantrine level has been shown to be an important determinant of treatment efficacy. To date no method has been published for the determination of lumefantrine after capillary sampling onto filter paper for field use. The aim of this work was to develop a method with adequate sensitivity for quantification of lumefantrine in capillary blood sampled onto filter paper. The method has been validated according to the current FDA guideline for bioanalytical method validation. Method: Whatman 31 ET Chr filter paper was pre-treated with an organic acid before sampling capillary blood to enable a high recovery of lumefantrine. Lumefantrine was extracted from the filter paper, then further purified using solid phase extraction and finally quantified with HPLC. Results: The between day variation is below 10 % over the range 0.4 to 25 µmol/l. The lower limit of quantification is 0.25 µmol/l in 100 µl capillary blood. No decrease in Lumefantrine concentration in dried blood spot is seen after 3 months at 37o C. The field sampling for lumefantrine assay with pre-treated Whatman 31 ET Chr has been tested in Tanzania with good results. Discussion: The field sampling for lumefantrine concentration assay with pre-treated Whatman 31 ET Chr has been evaluated and proven to be a valid method for field studies. The day 7 level after treatment can lumefantrine be accurately estimated in capillary blood to follow up compliance and efficacy. Validation data will be presented.

  • 9.
    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.

  • 10.
    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.

  • 11. Bwijo, B
    et al.
    Kaneko, A
    Takechi, M
    Zungu, I.L.
    Moriyama, Y
    Lum, J.K.
    Tsukahara, T.
    Mita, T
    Takahashi, N
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Björkman, A
    Kobayakawa, T
    High prevalence of quintuple mutant dphps/dhfr genes in Plasmodium falciparum infections seven years after introduction of sulfadoxine and Pyrimethamine as first line treatment in Malawi2003In: Acta Tropica, ISSN 0001-706X, E-ISSN 1873-6254, no 85, p. 363-373Article in journal (Refereed)
  • 12. Färnert, A
    et al.
    Lindberg, J
    Gil, P
    Swedberg, G
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Thapar, M.M
    Berezcky, S
    Björkman, A
    Lindegårdh, Niklas
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Evidence of Plasmodium falciparum malaria resistant to atovaquone and proguanil hydrochloride: case reports2003In: BMJ. British Medical Journal (International Ed.), ISSN 0959-8146, E-ISSN 0959-535X, no 326, p. 628-629Article in journal (Refereed)
  • 13. Jansson, R.
    et al.
    Malm, Mikaela
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Roth, C.
    Ashton, M.
    Enantioselective and dose dependent intestinal absorption of eflornithine in rats2007In: Tropical medicine & international health, ISSN 1360-2276, E-ISSN 1365-3156, Vol. 12, no s1, p. 245-246Article in journal (Other academic)
  • 14. Jansson, R.
    et al.
    Malm, Mikaela
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Roth, C.
    Ashton, M.
    Enantioselective and nonlinear intestinal absorption of eflornithine in the rat2008In: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 52, no 8, p. 2842-2848Article in journal (Refereed)
    Abstract [en]

    This study aimed to investigate if the absorption of the human African trypanosomiasis agent eflornithine was stereospecific and dose dependent after oral administration. Male Sprague-Dawley rats were administered single doses of racemic eflornithine hydrochloride as an oral solution (750, 1,500, 2,000, or 3,000 mg/kg of body weight) or intravenously (375 or 1,000 mg/kg of body weight). Sparse blood samples were obtained for determination of eflornithine enantiomers by liquid chromatography with evaporative light-scattering detection (lower limit of quantification [LLOQ], 83 mu M for 300 mu l plasma). The full plasma concentration-time profile of racemic eflornithine following frequent sampling was determined for another group of rats, using a high-performance liquid chromatography-UV method (LLOQ, 5 mu M for 50 mu l plasma). Pharmacokinetic data were analyzed in NONMEM for the combined racemic and enantiomeric concentrations. Upon intravenous administration, the plasma concentration-time. profile of eflornithine was biphasic, with marginal differences in enantiomer kinetics (mean clearances of 14.5 and 12.6 ml/min/kg for L- and D-eflornithine, respectively). The complex absorption kinetics were modeled with a number of transit compartments to account for delayed absorption, transferring the drug into an absorption compartment from which the rate of influx was saturable. The mean bioavailabilities for L- and D-eflornithine were 41% and 62%, respectively, in the dose range of 750 to 2,000 mg/kg of body weight, with suggested increases to 47% and 83%, respectively, after a dose of 3,000 mg/kg of body weight. Eflornithine exhibited enantioselective absorption, with the more potent L-isomer being less favored, a finding which may help to explain why clinical attempts to develop an oral treatment have hitherto failed. The mechanistic explanation for the stereoselective absorption remains unclear.

  • 15. 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.

  • 16. Lindegårdh, N
    et al.
    Ashley, E.A.
    Tarning, J
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Annerberg, A
    Singtoroj, T
    Ashton, M
    Nosten, F
    Day, N.P.J.
    White, N.J.
    Piperaquine, new findings2005In: International Congress for Tropical medicine and Malaria, Marseille, 2005Conference paper (Refereed)
  • 17.
    Lindegårdh, Niklas
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Development of field-adapted analytical methods for the determination of new antimalarial drugs in biological fluids2003Doctoral thesis, monograph (Other academic)
  • 18. 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.

  • 19.
    Lindegårdh, Niklas
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Ashton, M
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Automated Solid-Phase Extraction Method for the Determination of Piperaquine in Plasma by Peak Compression Liquid Chromatography2003In: Journal of Chromatographic Science, ISSN 0021-9665, E-ISSN 1945-239X, Vol. 41, no 1, p. 44-49Article in journal (Refereed)
  • 20.
    Lindegårdh, Niklas
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Ashton, M
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Automated Solid-Phase Extraction Method for the Determination of Piperaquine in Whole Blood by Rapid Liquid Chromatography2003In: Therapeutic Drug Monitoring, ISSN 0163-4356, E-ISSN 1536-3694, Vol. 25, no 5, p. 544-551Article in journal (Refereed)
  • 21.
    Lindegårdh, Niklas
    et al.
    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 highly lipophilic analytes and hydrophilic strong basic analytes. Method development- strategies and practical considerations2004In: PBA, Florens, Italien, 2004Conference paper (Other academic)
  • 22.
    Lindegårdh, Niklas
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    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 determination of atovaquone, progunail and its metabolites in plasma by automatic mixed mode solid phase extraction and LC2004In: PBA, Florens, Italien, 2004Conference paper (Other academic)
  • 23. 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.

  • 24.
    Lindkvist, Jenny
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Determination of sulfadoxine and sulfamethoxazole in capillary blood with different approaches of sample preparation.2007Licentiate thesis, monograph (Other academic)
  • 25.
    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 Technology and Business Studies, Chemical Engineering.
    Determination of sulfonamides from capillary blood on sampling paper with solid-phase extraction, liquid chromatography and UV detection. [Poster]2006In: Analysdagarna, Göteborg, 2006Conference paper (Other academic)
  • 26.
    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.

  • 27.
    Malm, Mikaela
    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 detection – Selection of regression model.2006In: Analysdagarna, Göteborg, 2006Conference paper (Other academic)
  • 28.
    Malm, Mikaela
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Development of analytical methods for determination of drugs, used against tropical diseases, in biological fluids2006Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The overall aim of this thesis was to develop analytical methods for determination of drugs, used against tropical diseases, in biological fluids. For the treatment of malaria, piperaquine (PQ) is used in combination with another antimalarial. Human African trypanosomiasis is treated with eflornithine (DFMO), a chiral drug administered as a racemic mixture. A method for determination of PQ in capillary blood applied and dried onto sampling paper has been developed and validated. This method uses perchloric acid and acetonitrile to extract PQ from the biological matrix and sampling paper. The liquid phase is then loaded onto a strong cation-exchange solid-phase extraction column. PQ and the IS are separated on a Chromolith Performance column at high flow rate, allowing fast chromatography, and detected with UV absorbance detection. Capillary blood sampling onto sampling paper facilitates clinical studies performed in the field, eliminates need of venipuncture, simplify storage as well as transportation and makes handling samples safer for laboratory personnel. A method for determination of underivatized DFMO enantiomers in plasma has been developed and validated. Proteins are percipitated with trichloro acetic acid and the liquid phase is loaded onto a strong cation-exhange solid-phase extraction column. D-DFMO and L-DFMO and the IS are separated on a Chirobiotic TAG column with a chiral stationary phase. Detection is performed using evaporative light-scattering detection. This method allows study of behavior of individual enantiomers in humans. There is an indication that D-DFMO and L-DFMO differ and this needs to be investigated further. Therefore, a chiral method of determination is of value. This method has also been evaluated for determination of DFMO enantiomers in cerebrospinal-fluid.

  • 29.
    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 and cerebrospinal fluid, by solid-phase extraction and liquid chromatography with evaporative light-scattering detection2005In: International Congress for Tropical medicine and Malaria, Marseille, 2005Conference paper (Refereed)
  • 30.
    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.

  • 31.
    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.
    Development of bioanalytical methods to support field based studies of drugs against tropical diseases in developing countries.2006In: Analysdagarna, Göteborg, 2006Conference paper (Other academic)
  • 32.
    Malm, Mikaela
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Lindegårdh, Niklas
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Automated solid-phase extraction method for the determination of piperaquine in capillary blood applied on sampling paper by liquid chromatography2004In: PBA, Florens, Italien, 2004Conference paper (Other academic)
  • 33.
    Malm, Mikaela
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Lindegårdh, Niklas
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Automated Solid-Phase Extraction method for the Determination of Piperaquine in Capillary/Venous Blood applied on Sampling Paper by Rapid Liquid Chromatography2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, no B 809, p. 43 - 49Article in journal (Refereed)
  • 34.
    Malm, Mikaela
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Lindkvist, Jenny
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Importance of pre-analytical factors contributing to measurement uncertainty, when determining sulfadoxine and sulfamethoxazole from capillary blood dried on sampling paper.2008In: Journal of Chromatographic Science, ISSN 0021-9665, E-ISSN 1945-239X, Vol. 46, no 9, p. 837-843Article in journal (Refereed)
    Abstract [en]

    A bioanalytical method is developed and validated for determination of sulfadoxine (SD) and sulfamethoxazole (SM) in 100 µL capillary blood dried on sampling paper (Whatman 31ET Chr). SD and SM are extracted with 2000 µL perchloric acid and the liquid phase is loaded onto ENV+ solid-phase extraction columns. SD, SM, and the internal standard are separated on a Purospher STAR RP-18 liquid chromatography column (150 × 4.6 mm) with a mobile phase consisting of acetonitrile–sodium acetate buffer pH 5.2, I = 0.1 (33:67, v/v). Analytes are detected with UV at 256 nm. Lower limit of quantitation is 5 µmol/L, where precisions are 4.2% and 3.9% for SD and SM, respectively. Three brands of sampling papers have been compared with respect to absorption properties, extraction recoveries, and variations. Punching out dried blood spots (DBS) instead of cutting spots into strips prior to extraction has been evaluated by examining precision and accuracy of SD and SM determinations. Importance of uniformity of types of sampling paper, sampling volume and biological matrix, benefit of punching out discs from DBS, and impact on absorption properties of different brands of sampling papers are discussed. Avoiding pre-analytical errors whenever possible results in concentrations determined being more accurate and precise.

  • 35.
    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.

  • 36.
    Römsing, Susanne
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Blessborn, Daniel
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    A METHOD FOR SCREENING SOME OF THE MOST COMMON ANTIMALARIAL DRUGS OF TODAY2008In: Pharmaceutical & Biomedical Analysis, Gdansk, Poland , 2008Conference paper (Refereed)
    Abstract [en]

    Malaria is an infectious decease caused by a one-celled parasite called Plasmodium. The most common types are falciparum and vivax malaria where falciparum is the deadliest form of malaria infection. Malaria is present in almost all tropical and sub-tropical regions around the world and there are at least 300 million cases of malaria in the world with over a million deaths every year. Some of the most frequently used antimalarial drugs are chloroquine, amodiaquine and sulphadoxine-pyrimethamine but drug resistance of the plasmodium falciparum parasite is spreading. The situation is especially serious in Southeast Asia where multi-drug resistant falciparum malaria is widespread. One factor that adds to drug resistance is poor compliance with dosing schedules. There are also increasing problems with counterfeit drugs that contain none or to low amount of antimalarial drug and this will also speed up drug resistance. It has recently become more common to combine different antimalarial drugs, preferably using drugs with different mechanisms of action, in order to increase efficacy and reduce the spread of malarial drug resistance within the malaria parasite populations. The aim of the developed screening method is to determine drug use in areas where a change in treatment policy has taken place since this would be more accurate than interviewing patients. Several of the drugs included in this screening method have relative long half-life e.g.chloroquine, pyrimethamine, mefloquine, and lumefantrine that are detectable at least 7 days after administration. Solid phase extraction is used as sample clean-up of plasma samples and separation is performed with gradient-LC and UV-detection at two different wavelengths. The developed method will be presented together with detection limits of the various drugs.

  • 37.
    Römsing, Susanne
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bökman, Fredrik
    Bergqvist, Yngve
    Dalarna University, School of Education, Health and Social Studies, Medical Science.
    Determination of melatonin in saliva using solid-phase extraction, high-performance liquid chromatography and fluorescence detection2006In: Scandinavian Journal of Clinical and Laboratory Investigation, ISSN 0036-5513, E-ISSN 1502-7686, Vol. 66, no 3, p. 181-190Article in journal (Refereed)
    Abstract [en]

    A sensitive bioanalytical method for the determination of melatonin in saliva by solid-phase extraction (SPE), high-performance liquid chromatography (HPLC) and fluorescence detection has been developed and validated. Saliva was collected with a Salivette((R)) sampling device (Sarstedt) and a mixed-mode SPE column was used for the extraction of melatonin and internal standard (N-acetyl-6-methoxytryptamine) from the saliva. Chromatographic separation was performed using a HyPurity C18 LC column (150x2.1 mm) with mobile phase acetonitrile-ammonium hydrogen carbonate buffer, 0.015 M, pH 6.8 (23:77, v/v). Excitation and emission wavelengths were set to 285 nm and 345 nm, respectively. The within-day precision for the method at 50 pmol/L was 7.9% and the between-day precision was 10.5%. The limit of quantification was 50 pmol/L.

  • 38.
    Römsing, Susanne
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bökman, Fredrik
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Determination of melatonin in saliva with solid-phase extraction, liquid chromatography and fluorescence detection2004In: PBA, Florens, Italien, 2004Conference paper (Other academic)
  • 39.
    Römsing, Susanne
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bökman, Fredrik
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Determination of melatonin in saliva with solid-phase extraction, liquid chromatography and fluorescence detection2003In: Analysdagarna, Göteborg, 2003Conference paper (Other academic)
  • 40.
    Römsing, Susanne
    et al.
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Ulfberg, J
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Determination of melatonin in human plasma with solid-phase extraction, high-performance liquid chromatography and fluorescence detection2003In: Scand J Clin Lab Invest, ISSN 1502-7686, no 63, p. 81-88Article in journal (Refereed)
  • 41. Singtoroj, T.
    et al.
    Tärning, J.
    Annerberg, A.
    Ashton, M.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    White, N.
    Lindegårdh, N.
    Day, N.A.
    A new approach to evaluate regression models during validation of bioanalytical assays2006In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 41, no 1, p. 219-227Article in journal (Refereed)
    Abstract [en]

    The quality of bioanalytical data is highly dependent on using an appropriate regression model for calibration curves. Non-weighted linear regression has traditionally been used but is not necessarily the optimal model. Bioanalytical assays generally benefit from using either data transformation and/or weighting since variance normally increases with concentration. A data set with calibrators ranging from 9 to 10 000 ng/mL was used to compare a new approach with the traditional approach for selecting an optimal regression model. The new approach used a combination of relative residuals at each calibration level together with precision and accuracy of independent quality control samples over 4 days to select and justify the best regression model. The results showed that log–log transformation without weighting was the simplest model to fit the calibration data and ensure good predictability for this data set.

  • 42. Tarning, J.
    et al.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Day, N. P.
    Bergquist, J.
    Arvidsson, B.
    White, N. J.
    Ashton, M.
    Lindegardh, N.
    Characterization of human urinary metabolites of the antimalarial piperaquine2006In: Drug Metabolism And Disposition, ISSN 0090-9556, E-ISSN 1521-009X, Vol. 34, no 12, p. 2011-2019Article in journal (Refereed)
    Abstract [en]

    Five metabolites of the antimalarial piperaquine (PQ) (1,3-bis-[4-(7chloroquinolyl-4)-piperazinyl-1]-propane) have been identified and their molecular structures characterized. After a p.o. dose of dihydroartemisinin-piperaquine, urine collected over 16 h from two healthy subjects was analyzed using liquid chromatography (LC)/UV, LC/tandem mass spectrometry (MS/MS), Fourier transform ion cyclotron resonance (FTICR)/MS, and H NMR. Five different peaks were recognized as possible metabolites [M1, 320 m/z; M2, M3, and M4, 551 m/z (PQ + 16 m/z); and M5, 567 m/z (PQ + 32 m/z)] using LC/MS/MS with gradient elution. The proposed carboxylic M1 has a theoretical monoisotopic molecular mass of 320.1166 m/z, which is in accordance with the FTICR/MS (320.1168 m/z) findings. The LC/MS/MS results also showed a 551 m/z metabolite (M2) with a distinct difference both in polarity and fragmentation pattern compared with PQ, 7-hydroxypiperaquine, and the other 551 m/z metabolites. We suggest that this is caused by N-oxidation of PQ. The results showed two metabolites (M3 and M4) with a molecular ion at 551 m/z and similar fragmentation pattern as both PQ and 7-hydroxypiperaquine; therefore, they are likely to be hydroxylated PQ metabolites. The molecular structures of M1 and M2 were also confirmed using H NMR. Urinary excretion rate in one subject suggested a terminal elimination half-life of about 53 days for M1. Assuming formation rate-limiting kinetics, this would support recent findings that the terminal elimination half-life of PQ has been underestimated previously.

  • 43. Tarning, J
    et al.
    Singtoroj, T
    Annerberg, A
    Ashton, M
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    White, N.J.
    Day, N
    Lingegårdh, N
    Development and validation of an automated solid phase extraction and liquid chromatographic method for determination of piperaquine in urine2005In: HPLC 2005, Stockholm, 2005Conference paper (Refereed)
  • 44. Tärning, J.
    et al.
    Singtoroj, T.
    Annerberg, A.
    Ashton, M.
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    White, N.
    Day, N.
    Lindegårdh, N.
    Development and validation of an automated solid phase extraction and liquid chromatographic method for determination of piperaquine in urine2006In: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 41, no 1, p. 213-218Article in journal (Refereed)
    Abstract [en]

    A sensitive and specific bioanalytical method for determination of piperaquine in urine by automated solid-phase extraction (SPE) and liquid chromatography (LC) has been developed and validated. Buffered urine samples (containing internal standard) were loaded onto mixed phase (cation-exchange and octylsilica) SPE columns using an ASPEC XL SPE robot. Chromatographic separation was achieved on a Chromolith Performance RP-18e (100 mm × 4.6 mm I.D.) LC column with phosphate buffer (pH 2.5; 0.1 mol/L)–acetonitrile (92:8, v/v). Piperaquine was analysed at a flow rate of 3 mL/min with UV detection at 347 nm. A linear regression model on log–log transformed data was used for quantification. Within-day precision for piperaquine was 1.3% at 5000 ng/mL and 6.6% at 50 ng/mL. Between-day precision for piperaquine was 3.7% at 5000 ng/mL and 7.2% at 50 ng/mL. Total-assay precision for piperaquine over 4 days using five replicates each day (n = 20) was 4.0%, 5.2% and 9.8% at 5000, 500 and 50 ng/mL, respectively. The lower limit of quantification (LLOQ) was set to 3 ng/mL using 1 mL of urine, which could be lowered to 0.33 ng/mL when using 9 mL of urine and an increased injection volume.

  • 45. Valecha, Neena
    et al.
    Mohanty, Suman
    Srivastava, Prakriti
    Sharma, Surya
    Tyagi, Prajesh
    Bergqvist, Yngve
    Dalarna University, School of Technology and Business Studies, Chemical Engineering.
    Ringwald, Pascal
    Short report: Efficacy of artemether-lumefantrine in area of high malaria endemicity in India and its correlation with blood concentration of lumefantrine2012In: American Journal of Tropical Medicine and Hygiene, ISSN 0002-9637, E-ISSN 1476-1645, Vol. 86, no 3, p. 395-397Article in journal (Refereed)
    Abstract [en]

    This study was conducted to correlate blood concentrations of lumefantrine with treatment outcome for patients with Plasmodium falciparum malaria when the drug was given without specific instructions for administration with food. Patients with P. falciparum malaria in the highly endemic state of Orissa, India, were enrolled during 2008 and followed-up for 28 days after admistration of artemether-lumefantrine for three days according to a World Health Organization protocol. Drug concentration in whole blood was determined by using blood spots placed on filter paper on day 7. The technology is suitable for field studies. One hundred percent of the patients had an adequate clinical and parasitological response. These results confirm the efficacy of artemether-lumefantrine in persons from poor tribal communities when given without specific instructions regarding co-administration with food, despite high inter-individual variability in blood concentrations of lumefantrine.

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