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  • 1.
    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.

  • 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.
    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.

  • 3. 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.

  • 4. 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.

  • 5. 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.

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