The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform
Caroline Schober - One of the best experts on this subject based on the ideXlab platform.
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Direct-injection high performance liquid chromatography ion trap mass spectrometry for the quantitative determination of olanzapine, clozapine and N-desmethylclozapine in human plasma.
Rapid communications in mass spectrometry : RCM, 2002Co-Authors: Manfred Kollroser, Caroline SchoberAbstract:A specific and sensitive direct-injection high performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) method has been developed for the rapid identification and quantitative determination of olanzapine, clozapine, and N-desmethylclozapine in human plasma. After the addition of the internal standard Dibenzepin and dilution with 0.1% formic acid, plasma samples were injected into the LC/MS/MS system. Proteins and other large biomolecules were removed during an online sample cleanup using an extraction column (1 x 50 mm i.d., 30 microm) with a 100% aqueous mobile phase at a flow rate of 4 mL/min. The extraction column was subsequently brought inline with the analytical column by automatic valve switching. Analytes were separated on a 5 microm Symmetry C18 (Waters) analytical column (3.0 x 150 mm) with a mobile phase of acetonitrile/0.1% formic acid (20:80, v/v) at a flow rate of 0.5 mL/min. The total analysis time was 6 min per sample. The inter- and intra-assay coefficients of variation for all compounds were
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Simultaneous determination of seven tricyclic antidepressant drugs in human plasma by direct-injection HPLC-APCI-MS-MS with an ion trap detector.
Therapeutic drug monitoring, 2002Co-Authors: Manfred Kollroser, Caroline SchoberAbstract:A sensitive and specific direct-injection high-performance liquid chromatography-atmospheric pressure chemical ionization tandem mass-spectrometry (HPLC-APCI-MS-MS) method has been developed for the rapid identification and quantitation of seven tricyclic antidepressants-amitriptyline, nortriptyline, doxepin, dosulepin, Dibenzepin, opipramol, and melitracen-in human plasma. After the addition of the internal standard lofepramine and dilution with 0.1% formic acid, plasma samples were injected into the LC-MS-MS system. Proteins and other large biomolecules were removed during an on-line sample cleanup using an Oasis extraction column (1 x 50 mm, ID, 30 microm) with a 100% aqueous mobile phase at a flow rate of 4 mL/min. The extraction column was subsequently brought in-line with the analytical column by automatic valve switching. Analytes were separated on a 5-microm Symmetry C18 (Waters) analytical column (3.0 x 150 mm, ID) using a step gradient of acetonitrile-0.1% formic acid at a flow rate of 0.6 mL/min. The total analysis time was only 12 minutes per sample. The interday and intraday coefficients of variation for all compounds were
Manfred Kollroser - One of the best experts on this subject based on the ideXlab platform.
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Direct-injection high performance liquid chromatography ion trap mass spectrometry for the quantitative determination of olanzapine, clozapine and N-desmethylclozapine in human plasma.
Rapid communications in mass spectrometry : RCM, 2002Co-Authors: Manfred Kollroser, Caroline SchoberAbstract:A specific and sensitive direct-injection high performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) method has been developed for the rapid identification and quantitative determination of olanzapine, clozapine, and N-desmethylclozapine in human plasma. After the addition of the internal standard Dibenzepin and dilution with 0.1% formic acid, plasma samples were injected into the LC/MS/MS system. Proteins and other large biomolecules were removed during an online sample cleanup using an extraction column (1 x 50 mm i.d., 30 microm) with a 100% aqueous mobile phase at a flow rate of 4 mL/min. The extraction column was subsequently brought inline with the analytical column by automatic valve switching. Analytes were separated on a 5 microm Symmetry C18 (Waters) analytical column (3.0 x 150 mm) with a mobile phase of acetonitrile/0.1% formic acid (20:80, v/v) at a flow rate of 0.5 mL/min. The total analysis time was 6 min per sample. The inter- and intra-assay coefficients of variation for all compounds were
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Simultaneous determination of seven tricyclic antidepressant drugs in human plasma by direct-injection HPLC-APCI-MS-MS with an ion trap detector.
Therapeutic drug monitoring, 2002Co-Authors: Manfred Kollroser, Caroline SchoberAbstract:A sensitive and specific direct-injection high-performance liquid chromatography-atmospheric pressure chemical ionization tandem mass-spectrometry (HPLC-APCI-MS-MS) method has been developed for the rapid identification and quantitation of seven tricyclic antidepressants-amitriptyline, nortriptyline, doxepin, dosulepin, Dibenzepin, opipramol, and melitracen-in human plasma. After the addition of the internal standard lofepramine and dilution with 0.1% formic acid, plasma samples were injected into the LC-MS-MS system. Proteins and other large biomolecules were removed during an on-line sample cleanup using an Oasis extraction column (1 x 50 mm, ID, 30 microm) with a 100% aqueous mobile phase at a flow rate of 4 mL/min. The extraction column was subsequently brought in-line with the analytical column by automatic valve switching. Analytes were separated on a 5-microm Symmetry C18 (Waters) analytical column (3.0 x 150 mm, ID) using a step gradient of acetonitrile-0.1% formic acid at a flow rate of 0.6 mL/min. The total analysis time was only 12 minutes per sample. The interday and intraday coefficients of variation for all compounds were
Katharina Rentsch - One of the best experts on this subject based on the ideXlab platform.
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Therapeutic drug monitoring of 13 antidepressant and five neuroleptic drugs in serum with liquid chromatography-electrospray ionization mass spectrometry.
Clinical Chemistry and Laboratory Medicine, 2003Co-Authors: Ursula Gutteck, Katharina RentschAbstract:Therapeutic drug monitoring of antipsychotic drugs has become more and more important in recent years, and a well-organized therapeutic drug monitoring service with fast turn-around times is very important. Therefore, an analytical method coupling high-performance liquid chromatography to mass spectrometry with electrospray ionization in the positive mode was established in our laboratory. Amitriptyline, citalopram, clomipramine (including norclomipramine), desipramine, Dibenzepin, doxepin (including nordoxepin), escitalopram, flupentixol, fluphenazine, fluvoxamine, imipramine, nortriptyline, opipramol, pipamperone, reboxetine, thioridazine, trimipramine and zuclopenthixol were separated on a reversed-phase C18 column. The mobile phase consisted of acetonitrile and ammonium acetate buffer pH 4. Because of different organic solvents used for the liquid-liquid extraction and the different volumes of mobile phases in which the residues were dissolved, four analytical systems had to be applied. Within the run-time of maximal 10 minutes the 13 antidepressant and five neuroleptic drugs were baseline separated on the corresponding mass-to-charge track. The calibration range of each drug was linear, all between-day coefficients of variation were below 7% and the recovery rates were between 60 and 103%. Using 1 ml of serum, the lower limits of quantification were between 1.2 and 54 nmol/l for the different drugs and below the therapeutic range for each of the different drugs.
Gilberto De Nucci - One of the best experts on this subject based on the ideXlab platform.
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ticlopidine quantification in human plasma by high performance liquid chromatography coupled to electrospray tandem mass spectrometry application to bioequivalence study
Journal of Mass Spectrometry, 2001Co-Authors: Ney Carter Do Carmo Borges, Gustavo D Mendes, Andre Borges, Sandro Oliveira, Rafael E Barrientosastigarraga, Gilberto De NucciAbstract:: A rapid, sensitive and specific method to quantify nevirapine in human plasma using Dibenzepine as the internal standard (IS) was developed and validated. The method employed a liquid-liquid extraction. The analyte and the IS were chromatographed on a C(18) analytical column, (150 x 4.6 mm i.d. 4 microm) and analyzed by tandem mass spectrometry in the multiple reaction monitoring mode. The method had a chromatographic run time of 5.0 min and a linear calibration curve over the range 10-5000 ng ml(-1) (r(2) > 0.9970). The between-run precision, based on the relative standard deviation for replicate quality controls was 1.3% (30 ng ml(-1)), 2.8% (300 ng ml(-1)) and 3.6% (3000 ng ml(-1)). The between-run accuracy was 4.0, 7.0 and 6.2% for the above-mentioned concentrations, respectively. This method was employed in a bioequivalence study of two nevirapine tablet formulations (Nevirapina from Far-Manguinhos, Brazil, as a test formulation, and Viramune from Boehringer Ingelheim do Brasil Quimica e Farmaceutica, as a reference formulation) in 25 healthy volunteers of both sexes who received a single 200 mg dose of each formulation. The study was conducted using an open, randomized, two-period crossover design with a 3 week washout interval. The 90% confidence interval (CI) of the individual ratio geometric mean for Nevirapina/Viramune was 96.4-104.5% for AUC((0-last)), 91.4-105.1% for AUC((0-infinity)) and 95.3-111.6% for C(max) (AUC = area under the curve; C(max) = peak plasma concentration). Since both 90% CI for AUC((0-last)) and AUC((0-infinity)) and C(max) were included in the 80-125% interval proposed by the US Food and Drug Administration, Nevirapina was considered bioequivalent to Viramune according to both the rate and extent of absorption.
Jos H Beijnen - One of the best experts on this subject based on the ideXlab platform.
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quantification of protease inhibitors and non nucleoside reverse transcriptase inhibitors in dried blood spots by liquid chromatography triple quadrupole mass spectrometry
Journal of Chromatography B, 2008Co-Authors: R Ter Heine, Hilde Rosing, E C M Van Gorp, J W Mulder, W A Van Der Steeg, Jos H Beijnen, Alwin D R HuitemaAbstract:Abstract A bioanalytical method for the determination of most commonly prescribed protease inhibitors (atazanavir, darunavir, lopinavir and ritonavir) and non-nucleoside reverse transcriptase inhibitors (efavirenz and nevirapine) was developed and validated according to FDA guidelines. In brief, dried blood spots were punched out of a collection paper with a 0.25 in. diameter punch. The analytes were extracted from the punched-out disc using a mixture of acetonitrile, methanol and 0.2M zinc sulphate in water (1:1:2, v/v/v) containing the internal standards Dibenzepine, 13C6-efavirenz and D5-saquinavir. 20 μL of the extract was injected onto the reversed-phase C18 column (150 mm × 2.0 mm) for separation from endogenous compounds and the analytes were quantified using a triple quadrupole mass spectrometer. The analytical run time was only 10 min. Validated concentration ranges covered the ranges encountered in routine clinical practice. The assay was linear over the concentration ranges tested (0.1–20 mg/L for atazanavir, lopinavir, nevirapine and efavirenz and 0.05–10 mg/L for darunavir and ritonavir). Accuracies and inter- and intra-run precisions at all levels ranged from 96.2 to 113.9% and 3.1 to 13.3%, respectively. Analytes in dried blood spots were stable for at least 7 days at 30 °C. The method enabled patient-friendly sample collection, easy and cheap sample shipment and non-hospital based sampling for therapeutic drug monitoring and pharmacokinetic studies.
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fast and simultaneous determination of darunavir and eleven other antiretroviral drugs for therapeutic drug monitoring method development and validation for the determination of all currently approved hiv protease inhibitors and non nucleoside revers
Rapid Communications in Mass Spectrometry, 2007Co-Authors: Rob Ter Heine, Hilde Rosing, Alwin D R Huitema, Carolien G Alderdenlos, Michel J X Hillebrand, Eric C M Van Gorp, Jos H BeijnenAbstract:: For the quantification of all currently approved non-nucleoside reverse transcriptase inhibitors and protease inhibitors, including the new protease inhibitor darunavir and the active nelfinavir metabolite M8, an assay was developed, using liquid chromatography coupled with tandem mass spectrometry. The sample pretreatment consisted of a protein precipitation with a mixture of methanol and acetonitrile using only 100 microL plasma. Chromatographic separation was performed on a reversed-phase C18 column (150 x 2.0 mm, particle size 5 microm) with a quick stepwise gradient using an acetate buffer (pH 5) and methanol, at a flow rate of 0.25 mL/min. The analytical run time was only 10 min. The triple quadrupole mass spectrometer was operated in the positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over a range of 0.1 to 20 microg/mL for amprenavir, atazanavir, efavirenz, indinavir, lopinavir, nelfinavir, the active nelfinavir metabolite M8, nevirapine and ritonavir, a range of 0.05 to 10 microg/mL for saquinavir and darunavir and a range of 0.5 to 100 microg/mL for tipranavir, based on observed concentration ranges in patients treated with these drugs. D5-squinavir, D6-indinavir, 13C6-efavirenz and Dibenzepine were used as internal standards. The method was proven to be specific, accurate, precise and robust. Accuracies ranged from 88.5% to 102.2% and all precisions were less than 9.5%. Furthermore, the assay demonstrates a high sensitivity for all analytes and the stepwise gradient allows addition of new analytes into the same method. The method is now successfully applied for routine therapeutic drug monitoring and pharmacokinetic studies in HIV-infected patients.