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  • 1.
    Blessborn, Daniel
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Neamin, G.
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Lindegårdh, N.
    A new approach to evaluate stability of amodiaquine and its metabolite in blood and plasma2006Ingår i: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 41, nr 1, s. 207-212Artikel i tidskrift (Refereegranskat)
    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. Goos, Elke
    et al.
    Hippler, Horst
    Kachiani, Chatuna
    Svedung, Harald
    Collisional energy transfer in CH3 radical decomposition—experiment versus theory2002Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 4, s. 4372-4378Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experimentally determined incubation times in the thermal decomposition of methyl radicals were used to obtain collisional energy transfer probability information by adopting a discrete vibrational energy level masterequation scheme with specific rate constants from the statistical adiabatic channel model. The agreement with information from classical molecular dynamic, MD, simulations of CH3–Ar collisions was shown to be remarkably good. Results from MD simulations also support the assumption of thermally equilibrated rotations used here and in earlier work. The sensitivity of the pressure fall-off behaviour of the decomposition channels to remaining uncertainties in the energy transfer profiles is shown to be significant, in this case, as a consequence of the large number of collisions needed to reach activation. Nevertheless, we find classical molecular dynamics simulation to be useful and a good starting point in obtaining the collisional energy transfer kernel to be used in master-equation calculations treating the most obvious quantum effects through the use of discrete energy levels at low energies.

  • 3. Jansson, R.
    et al.
    Malm, Mikaela
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Roth, C.
    Ashton, M.
    Enantioselective and dose dependent intestinal absorption of eflornithine in rats2007Ingår i: Tropical medicine & international health, ISSN 1360-2276, E-ISSN 1365-3156, Vol. 12, nr s1, s. 245-246Artikel i tidskrift (Övrigt vetenskapligt)
  • 4. Jansson, R.
    et al.
    Malm, Mikaela
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Roth, C.
    Ashton, M.
    Enantioselective and nonlinear intestinal absorption of eflornithine in the rat2008Ingår i: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 52, nr 8, s. 2842-2848Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Kostela, Johan
    Uppsala Universitet.
    Electrochemical Behavior of Redox Molecules in Michelles and in a Bicontinous Cubic Phase2003Licentiatavhandling, monografi (Övrigt vetenskapligt)
  • 6.
    Kostela, Johan
    et al.
    Uppsala Universitet.
    Elmgren, Maja
    Uppsala Universitet.
    Almgren, Mats
    Uppsala Universitet.
    Electrochemical properties and diffusion of a redox active surfactant incorporated in bicontinuous cubic and lamellar phase2005Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 50, nr 16-17, s. 3333-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this study was to investigate the electrochemical behaviour of the divalent redox active surfactant, N-cetyl-N′-methylviologen (CMV), in bicontinuous cubic and lamellar phases. The liquid crystalline phases were prepared from the system glycerolmonooleate (GMO)–water (and brine)–cationic surfactant. A comparison of the phase behaviour of GMO with the monovalent cetyltrimethylammonium bromide (CTAB) and the divalent CMV surfactant showed that the surfactants gave about the same effect at the same surface charge density. The electrochemical measurements were made with a mixture of CTAB and CMV as the surfactant. Cyclic voltammetry was used to study the electrochemistry of CMV incorporated in the cubic and lamellar phases that were spread on a gold electrode. The E0-values in the cubic samples were more negative (−0.55 V versus SCE) than in the lamellar samples (−0.53 V versus SCE). This can be explained by the higher charge density in the lamellar phase. The diffusion coefficients were also measured in the cubic phase. The mass transport is slowed down about fifty times in the cubic phase compared to in the pure electrolyte. The concentration dependence on the diffusion coefficient was also investigated. No electron hopping could be observed, which suggest that diffusional movement of the redox probe is the main source of charge transport. By placing the samples on a conducting glass slide, spectroelectrochemical investigations were performed. In the lamellar phase strong dimerization was detected at high concentration of viologen, but much less in the cubic phase.

  • 7.
    Kostela, Johan
    et al.
    Uppsala universitet.
    Elmgren, Maja
    Uppsala universitet.
    Hansson, Per
    Uppsala universitet.
    Almgren, Mats
    Uppsala universitet.
    Electrochemical properties of an amphiphilic viologen in differently charged micelles2002Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 536, nr 1-2, s. 97-107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electrochemical properties of N-tetradecyl-N′-methylviologen (TMV) in differently charged micelles were studied with a glassy carbon electrode using electrochemical techniques. The redox potential varied depending on the charge of the surrounding surfactants. When the viologen was situated in cationic micelles the redox potential for the 2+/1+ reaction was more positive than when situated in negatively charged micelles. The non-ionic micelles destabilised the 2+-state most showing the highest redox potentials. From studies of several different cationic micelles it was concluded that the most important parameter for the redox potential was the surface charge density. A calculation based on a simple model confirmed this. Other interactions also influenced the stability of the redox states. Adsorption, desorption and reorganisation of the surfactants at the electrode surface caused capacitive currents. To control the nonfaradaic current, differential pulse voltammetry (DPV) was used in addition to cyclic voltammetry.

  • 8.
    Kostela, Johan
    et al.
    Uppsala Universitet.
    Elmgren, Maja
    Uppsala Universitet.
    Kadi, Mari
    Uppsala Universitet.
    Almgren, Mats
    Redox activity and diffusion of hydrophilic, hydrophobic, and amphiphilic redox active molecules in a bicontinuous cubic phase2005Ingår i: The Journal of Physical Chemistry. B, ISSN 1520-6106, Vol. 109, nr 11, s. 5073-Artikel i tidskrift (Refereegranskat)
  • 9.
    Malm, Mikaela
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Lindkvist, Jenny
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Importance of pre-analytical factors contributing to measurement uncertainty, when determining sulfadoxine and sulfamethoxazole from capillary blood dried on sampling paper.2008Ingår i: Journal of Chromatographic Science, ISSN 0021-9665, E-ISSN 1945-239X, Vol. 46, nr 9, s. 837-843Artikel i tidskrift (Refereegranskat)
    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.

  • 10. Nordholm, Strure
    et al.
    Börjesson, Lars Erik Börje
    Ming, Liu
    Svedung, Harald
    Progress on the modeling of the collisional energy transfer mechanism in unimolecular reactions1997Ingår i: Berichte Der Bunsen-Gesellschaft: Physical Chemistry, Chemical Physics, ISSN 0005-9021, Vol. 101, s. 574-580Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The RRKM theory of unimolecular reaction rates is a statistical mechanical theory based on an assumption of microcanonical equilibrium in the reactant phase space. The energy transfer in reactant medium collisions was originally described by a canonical strong collision assumption, i.e., an assumption of full thermal equilibration in each collision. In our work we first introduce a microcanonical strong collision assumption which gives the RRKM theory a consistent form. We then introduce parametrizations of the degree of weakness (nonergodicity) of the collisions. A concept of collision efficiency is defined. The weakness of the collision is expressed in terms of reduced subsets of active reactant and medium degrees of freedom. The corresponding partially ergodic collision theory (PECT) yields physical functional forms of the collisional energy transfer kernel P(E,E). In order to resolve the energy and temperature dependence and the dependence on interaction strength a multiple encounter theory is introduced (PEMET). Initially each encounter may be described by a semiempirical PECT model. Eventually the encounters may be resolved by quantum dynamical calculations of the semiclassical or CAQE (classical approach quantum encounter) type. Simple statistical collision models only distinguish between hits and misses . In reality the energy transfer efficiency exhibits characteristic fall off with increasing impact parameter b. This b-dependence can be explicitly accounted for in the master equation for the reaction rate coefficient.

  • 11. Nordholm, Sture
    et al.
    Svedung, Harald
    Nyeland, Carl
    Simple analysis of intermolecular potentials: The mBq pair potential for collisions and energy transfer2001Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 3, nr 12, s. 2209-2215Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have investigated and compared four different theoretical and empirical procedures for the generation of simple but reliable pairwise atomÈatom potentials to be used as components in the construction of intermolecular potentials. A method is proposed wherein the parameters of a modified Buckingham potential with atomic monopoles (mBq potential) is obtained by Ðtting to MP2 energies for interacting molecules confined to approach in selected symmetry directions. The results for 31 atomic pairs are compared with earlier results obtained by electron gas density functional theory, best available quantum chemical calculation or spectroscopic Ðt. The evidence is that the mBq potentials can be of signiÐcant practical value in a wide range of applications.

  • 12.
    Römsing, Susanne
    et al.
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Bökman, Fredrik
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Medicinsk vetenskap.
    Determination of melatonin in saliva using solid-phase extraction, high-performance liquid chromatography and fluorescence detection2006Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation, ISSN 0036-5513, E-ISSN 1502-7686, Vol. 66, nr 3, s. 181-190Artikel i tidskrift (Refereegranskat)
    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.

  • 13.
    Römsing, Susanne
    et al.
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Kemi.
    Lindegardh, Niklas
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Medicinsk vetenskap.
    Determination of tafenoquine in dried blood spots and plasma using LC and fluorescence detection2011Ingår i: Bioanalysis, ISSN 1757-6180, E-ISSN 1757-6199, Vol. 3, nr 16, s. 1847-1853Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: The growing problem of parasites developing resistance to the traditional antimalarial drugs makes the development of new effective and safe drugs crucial. Tafenoquine is a new promising antimalarial drug for prophylaxis and treatment.

    Results: A bioanalytical method for the determination of tafenoquine in 100 mu l of capillary blood applied onto sampling paper and in 100 mu l of plasma has been developed and validated. The Whatman 31 ET Chr paper was treated with 0.6 mol/l tartaric acid to improve the extraction recovery and solid-phase extraction was used for cleanup procedure of the blood samples. Plasma samples were precipitated with methanol. Tafenoquine and internal standard were separated on a Zorbax SB-CN column by reversed-phase LC and detected with fluorescence detection at 262 and 470 nm. The within- and between-day variations were below 10 and 14%, respectively, over the range 50-200 nmol/l for capillary blood on sampling paper and below 6 and 10% for plasma samples. The LLOQ of the method was 50 nmol/l.

    Conclusion: The developed method has adequate sensitivity and is highly suitable for clinical studies in dried blood spots and plasma.

  • 14. Sahlin, K
    et al.
    Sallstedt, E-K
    Bishop, D
    Tonkonogi, Michail
    Högskolan Dalarna, Akademin Utbildning, hälsa och samhälle, Medicinsk vetenskap.
    Turning down lipid oxidation during heavy exercise--what is the mechanism?2008Ingår i: Journal of Physiology and Pharmacology, ISSN 0867-5910, E-ISSN 1899-1505, Vol. 59, nr 4, s. 19-30Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A high potential for lipid oxidation is a sign of metabolic fitness and is important not only for exercise performance but also for health promotion. Despite considerable progress during recent years, our understanding of how lipid oxidation is controlled remains unclear. The rate of lipid oxidation reaches a peak at 50-60% of (V) over dotO(2) (max) after which the contribution of lipids decreases both in relative and absolute terms. In the high-intensity domain (> 60% (V) over dotO(2 max)), there is a pronounced decrease in energy state, which will stimulate the glycolytic rate in excess of the substrate requirements of mitochondrial oxidative processes. Accumulation of glycolytic products will impair lipid oxidation through an interaction with the carnitine-mediated transfer of FA into mitochondria. Another potential site of control is Acyl-CoA synthetase (ACS), which is the initial step in FA catabolism. The activity of ACS may be under control of CoASH and energy state. There is evidence that additional control points exist beyond mitochondrial influx of fatty acids. The electron transport chain (ETC) with associated feed-back control by redox state is one suggested candidate. In this review it is suggested that the control of FA oxidation during heavy exercise is distributed between ACS, CPT1, and ETC.

  • 15. Singtoroj, T.
    et al.
    Tärning, J.
    Annerberg, A.
    Ashton, M.
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    White, N.
    Lindegårdh, N.
    Day, N.A.
    A new approach to evaluate regression models during validation of bioanalytical assays2006Ingår i: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 41, nr 1, s. 219-227Artikel i tidskrift (Refereegranskat)
    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.

  • 16. Svedung, Harald
    Dynamical theory of collisional energy transfer between reactant and medium molecules2001Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 17. Svedung, Harald
    et al.
    Börjesson, Lars Erik Börje
    Markovic, Nikola
    Nordholm, Sture
    The mechanism of energy transfer in H2O-H2O collisions - a molecular dynamics simulation1998Ingår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 236, nr 1-3, s. 189-205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Earlier work on the activation-deactivation mechanism of gas phase unimolecular reactions is extended to the study of the detailed energy transfer mechanism in collisions of water molecules. Molecular dynamics simulations of binary collisions between a reactant water molecule at high internal energy with medium molecules at various selected initial temperatures are compared with results from approximate statistical theory. Energy transfer is related to i. interaction strength, ii. hard atom–atom encounters, iii. multiple minima in the center of mass separation, iv. collision lifetime and v. anharmonicity of the intramolecular potential function. The observed trends are interpreted within the framework of the partially ergodic multiple encounter theory PEMET. of collisional energy transfer. By comparison with typical stable molecule collisions the water–water collisions are more efficient as a reflection of the strong hydrogen bonding interactions. A good agreement between PEMET and molecular dynamics simulations over a wide range of interaction strengths and initial reactant energies is shown, indicating the possibility of a priori use of the PEMET model.

  • 18. Svedung, Harald
    et al.
    Krems, Roman
    Markovic, Nikola
    Nordholm, Sture
    Pair-potential model for simulation of collisional energy transfer: quantum effects and hardness dependence2001Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 3, nr 12, s. 2216-2222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A study of the sensitivity of energy transfer efficiency in molecular collisions is reported with special focus on the hardness of repulsion in atomÈatom contact. An improved pair potential is proposed with independent parameters for atomic size, attraction and hardness determined speciÐcally for a chosen atom pair by supermolecular quantum chemistry or equivalent experimental interaction data. Colinear and full 3D collisions of atomÈdiatomic molecule collisions are simulated using classical or quantum (in the colinear case) mechanics to illustrate : (i) remarkable agreement between classical and quantum dynamics for VÈT energy transfer ; (ii) greater sensitivity to hardness than to attraction and (iii) suitability of MP2 energies in symmetry constrained axial directions as a data set for the determination of pair-potential parameters.

  • 19. Svedung, Harald
    et al.
    Markovic, Nikola
    Nordholm, Sture
    Collisional deactivation of CF3I - a molecular dynamics simulation1999Ingår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 248, nr 2-3, s. 195-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The detailed mechanisms of ro-vibrational energy transfer in collisions between CF3I and argon or propane are investigated. Molecular dynamics simulations of collisions between a reactant CF3I molecule at energies from 50 to 200 kJrmol with medium argon or propane at selected initial temperatures are interpreted in terms of ergodic collision limits. The intramolecular potential used for CF3I is a Morse-stretchrharmonic-bend type function with parameters fitted to equilibrium structure, normal mode frequencies and dissociation energies. Simple generic Buckingham type pair-potentials are used for intermolecular atom–atom interactions. Energy transfer is related to i. geometry of collision, ii. impact parameter, iii. number of atom–atom encounters, iv. average dynamical hardness of interaction at atom–atom collisions, v. number of minima in the center of mass separation and vi. lifetime of the collisional complex. The energy transfer in our molecular dynamics calculations is compared with experimental results for the same colliders. The observed trends are interpreted in terms of detailed collisional mechanisms. Our results highlight the importance of rotational excitation and the repulsive part of the intermolecular potential.

  • 20. Tarning, J.
    et al.
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Day, N. P.
    Bergquist, J.
    Arvidsson, B.
    White, N. J.
    Ashton, M.
    Lindegardh, N.
    Characterization of human urinary metabolites of the antimalarial piperaquine2006Ingår i: Drug Metabolism And Disposition, ISSN 0090-9556, E-ISSN 1521-009X, Vol. 34, nr 12, s. 2011-2019Artikel i tidskrift (Refereegranskat)
    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.

  • 21. Tärning, J.
    et al.
    Singtoroj, T.
    Annerberg, A.
    Ashton, M.
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    White, N.
    Day, N.
    Lindegårdh, N.
    Development and validation of an automated solid phase extraction and liquid chromatographic method for determination of piperaquine in urine2006Ingår i: Journal of Pharmaceutical and Biomedical Analysis, ISSN 0731-7085, E-ISSN 1873-264X, Vol. 41, nr 1, s. 213-218Artikel i tidskrift (Refereegranskat)
    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.

  • 22. Valecha, Neena
    et al.
    Mohanty, Suman
    Srivastava, Prakriti
    Sharma, Surya
    Tyagi, Prajesh
    Bergqvist, Yngve
    Högskolan Dalarna, Akademin Industri och samhälle, Kemiteknik.
    Ringwald, Pascal
    Short report: Efficacy of artemether-lumefantrine in area of high malaria endemicity in India and its correlation with blood concentration of lumefantrine2012Ingår i: American Journal of Tropical Medicine and Hygiene, ISSN 0002-9637, E-ISSN 1476-1645, Vol. 86, nr 3, s. 395-397Artikel i tidskrift (Refereegranskat)
    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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