Didier Ortelli

Publications (19) View all

• Article: Analysis of dihydroartemisinin in plasma by liquid chromatography—Mass spectrometry

  D. Ortelli, S. Rudaz, E. Cognard, J. -L. Veuthey
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  ABSTRACT: Artemisinin (ART), or qinghaosu, a sesquiterpene lactone containing an endoperoxide bridge, is an efficient drug against chloroquine-resistant strains ofPlasmodium falciparum in the treatment of cerebral malaria. ART and its derivatives are rapidly metabolized into dihydroartemisinin (DHA), which is responsible for the antimalarial activity. After a simple liquid-liquid extraction (LLE), determination of DHA in plasma was conducted by liquid chromatography-mass spectrometry (LC-MS) with an electrospray ionization (ESI) interface. Addition of dodecylamine to the mobile phase and analysis in selected-ion monitoring (SIM) mode resulted in enhanced sensitivity and selectivity. Use of a primary amine, e.g. propylamine, pentylamine, hexylamine or dodecylamine, in the mobile phase can inhibit the formation of multimer clusters and ion adducts by forming one dominating species (analyte-primary amine adduct). Dodecylamine (DDA) was selected after several assays as a competitive agent for adduct formation. The procedure was validated and precision and accuracy were found to be good for the matrix studied. The method was applied to samples provided by patients receiving artesunate (ARS) for antimalarial treatment.
  Chromatographia 04/2012; 52(7):445-450. · 1.20 Impact Factor
• Article: Analysis of Chloramphenicol Residues in Honey by Liquid Chromatography–Tandem Mass Spectrometry

  D. Ortelli, P. Edder, C. Corvi
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  ABSTRACT: Antibiotics are often used in bee-keeping to control European and American foulbrood. The broad spectrum antibiotic chloramphenicol (CAP) was used for curative purposes in veterinary medicine, but is now forbidden in numerous countries, although still used in south-east Asia. A liquid-chromatographic method with tandem mass spectrometric detection (LC–MS–MS) has been developed for analysis of sub-g kg–1 residues of chloramphenicol in honey. Results from full validation of the procedure and analysis of 75 honey samples obtained commercially in Switzerland are presented. These show the method is satisfactory and useful for monitoring chloramphenicol residues in honey.
  Chromatographia 12/2003; 59(1):61-64. · 1.20 Impact Factor
• Article: Use of large particles support for fast analysis of methadone and its primary metabolite in human plasma by liquid chromatography-mass spectrometry.

  S Souverain, S Rudaz, D Ortelli, E Varesio, J L Veuthey
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  ABSTRACT: A bioanalytical method was developed for the quantitation of methadone (MTD) and its primary metabolite, (EDDP) in plasma. The extraction step was performed within a capillary column packed with large particles (35x0.3 mm I.D.; d(p) 30 micrometer) at high flow-rate conditions (450 microliter/min). The separation was performed on a microbore analytical column (55x2 mm I.D.; d(p) 3 micrometer) coupled to a mass spectrometer (MS). This procedure was based on a column-switching unit. Analytes of interest were retained on the precolumn by hydrophobic interactions and backflushed from the precolumn to the analytical column. The detection was carried out with a MS single quadrupole equipped with an electrospray interface. The total analysis time was 6 min. The limits of quantification were evaluated at 10 and 25 ng/ml for MTD and EDDP, respectively. At this level, good accuracies were obtained for both analytes with repeatability values less than 18%.
  Journal of Chromatography B 02/2003; 784(1):117-23. · 2.89 Impact Factor
• Article: Restricted access materials for fast analysis of methadone in serum with liquid chromatography‐mass spectrometry

  Didier Ortelli, Serge Rudaz, Sandrine Souverain, Jean‐Luc Veuthey
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  ABSTRACT: Restricted access materials (RAM) which allow direct injection of biological fluids in a chromatographic system were evaluated for the direct analysis of methadone (MTD) in serum by liquid chromatography (LC) and mass spectrometry (MS). Two methods were developed for the determination of methadone and its major metabolite, EDDP, in serum samples in a concentration range of 10 to 500 ng mL–1. The first method used the single column approach with a Pinkerton GFF II (100×2.1 mm ID) analytical column. In this mode, the column is the same for the sample preparation and the analysis. The total analysis time was less than 15 min with a limit of quantification of 10 ng mL—1. At this level, repeatability values were 11.8% and 15.8% for MTD and EDDP, respectively. The second method used a column-switching device. A RP-4 ADS (25×2 mm ID) precolumn was coupled to a LC column and achieved a total analysis time of less than 8 minutes. At the LOQ, repeatability values were 3.2% and 7.6% for MTD and EDDP, respectively. Compared to a classical liquid-liquid extraction, RAM proved to be very convenient stationary phases. Both methods a gave short analysis time with a minimum of sample handling and allowed quantitative determination of MTD and EDDP in serum.
  Journal of Separation Science 03/2002; 25(4):222 - 228. · 2.73 Impact Factor
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  Article: Enantioselective analysis of methadone in saliva by liquid chromatography-mass spectrometry.

  D Ortelli, S Rudaz, A F Chevalley, A Mino, J J Deglon, L Balant, J L Veuthey
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  ABSTRACT: Saliva was tested and evaluated as a biological matrix for methadone (Mtd) monitoring. Conventional method using a narrow bore C18 column, and an enantioselective method using a narrow bore alpha1-acid glycoprotein column, were developed using liquid chromatography coupled with a mass spectromeric (MS) detector. After optimisation of MS conditions by flow injection analysis, selected ion monitoring detection was used to enhance sensitivity. The total Mtd concentration and the enantiomeric ratio in saliva were validated using an experimental design. The methods were applied to samples provided by heroin addicts undergoing a Mtd treatment. Results on total Mtd determination showed a very poor correlation between saliva and serum, whereas the enantiomeric ratios of Mtd gave a very good one.
  Journal of Chromatography 03/2000; 871(1-2):163-72. · 4.53 Impact Factor