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A fully automated high-throughput liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed for the determination of roxithromycin in human plasma. The plasma samples were treated by liquid-liquid extraction (LLE) in 2.2mL 96-deep-well plates. Roxithromycin and the internal standard clarithromycin were extracted from 100 μL of human plasma by LLE, using methyl t-butyl ether as the organic solvent. All liquid transfer steps were performed automatically using robotic liquid handling workstations. After vortexing, centrifugation and freezing, the supernatant organic solvent was evaporated and reconstituted. Sample analysis was performed by reversed-phase LC-MS/MS, with positive ion electrospray ionization, using multiple-reaction monitoring. The method had a very short chromatographic run time of 1.6 min. The calibration curve was linear for the range of concentrations 50.0-20.0 × 103 ng mL-3. The proposed method was fully validated and it was proven to be selective, accurate, precise, reproducible and suitable for the determination of roxithromycin in human plasma. Therefore, it was applied to the rapid and reliable determination of roxithromycin in a bioequivalence study after per os administration of 300 mg tablet formulations of roxithromycin. Copyright © 2007 John Wiley & Sons, Ltd.

In the current study, a semi-automated, 96-well format, solid-phase extraction (SPE), analytical column-switching method for alendronate determination in human urine is developed, validated and applied to a bioequivalence study. The current protocol was a substantial improvement of an existing classical method. A robotic liquid handling system was employed to simplify and reduce the time of sample preparation procedure. Automated SPE was carried out using a 96-well cartridge plate and a vacuum control system. Urine samples were determined by applying a column-switching protocol with fluorescence detection. Analysis time, due to the column-switching procedure, was about half of the conventional LC approach (11.5 min instead of 21 min). The method application required the determination of alendronate in urine samples obtained from 96 healthy volunteers as part of a bioequivalence study of two 70 mg alendronate sodium tablets. All major pharmacokinetic parameters of the bioequivalence study were estimated and reported. © 2006 Elsevier B.V. All rights reserved.

A fully automated high-throughput liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed for terbinafine quantification in human plasma. The plasma samples were treated by liquid-liquid extraction (LLE) in 2.2 mL 96-deepwell plates. Terbinafine and the internal standard (IS) N-methyl-1-naphthalenemethylamine were extracted from human plasma by LLE, using a mixture of methyl t-butyl ether (MTBE)-hexane (70:30, v/v) as the organic solvent. All liquid transfer steps, including preparation of calibration standards and quality control samples, as well as the addition of the IS, were performed automatically by using robotic liquid handling workstations. After vortexing, centrifugation and freezing, the supernatant organic solvent was evaporated and reconstituted in a small volume of a reconstitution solution. Sample analysis was performed by reversed-phase LC-MS/MS, with positive ion electrospray ionization, using multiple reaction monitoring (MRM). The method had a very short sample preparation time and a chromatographic run time of 2.2 min. It was proved to have excellent sensitivity, specificity, accuracy as well as inter- and intraday precision for the quantification of terbinafine in human plasma. The calibration curve was linear for the range of concentrations 5.0-2000.0 ng/mL. The proposed method was applied to the rapid and reliable determination of terbinafine in a bioequivalence study after per os administration of 250 mg tablet formulations of terbinafine. Copyright © 2007 John Wiley & Sons, Ltd.

A semi-automated liquid chromatography-tandem mass spectrometry (LC/MS/MS) method was developed for the simultaneous quantification of the antifungal drug itraconazole (ITZ) and its coactive metabolite hydroxyitraconazole (OH-ITZ) in human plasma. The plasma samples underwent liquid-liquid extraction (LLE) in 2.2 mL 96 deepwell plates. ITZ, OH-ITZ and the internal standard (IS) R51012 were extracted from plasma, using a mixture of acetonitrile (ACN) and methyl t-butyl ether (MTBE) as the organic solvent. This specific mixture, due to its composition, had a significant impact on the performance of the assay. All liquid transfer steps, including preparation of calibration standards and quality control samples as well as the addition of the IS, were performed automatically using robotic liquid handling workstations for parallel sample processing. After vortexing, centrifugation and freezing, the supernatant organic solvent was evaporated. The analytes and IS were dissolved in a small volume of a reconstitution solution, an aliquot of which was analyzed by combined reversed phase LC/MS/MS, with positive ion electrospray ionization and a TurboIonSpray interface, using multiple reactions monitoring (MRM). The method was shown to be sensitive and specific to both ITZ and OH-ITZ, it revealed excellent linearity for the range of concentrations 2-500 ng mL-1 for ITZ and 4-1000 ng mL-1 for OH-ITZ, it was very accurate and it gave very good inter- and intra-day precisions. The proposed high-throughput method was employed in a bioequivalence study after per os administration of two 100 mg tablets of ITZ, and it allowed this study to be completed in under four days.

A rapid and sensitive LC-MS/MS method for the quantification of ondansetron was developed and validated. The plasma samples were treated by a semi-automated liquid-liquid extraction (LLE) in 1.2 mL 96-well format micro-tubes. Ondansetron and the internal standard (IS) granisetron were analyzed by combined reversed phase LC-MS/MS, with positive ion electrospray ionization, using multiple reactions monitoring (MRM). The statistical evaluation for this method reveals excellent linearity, accuracy and precision values for the range of concentrations 0.25-40.0 ng/mL. The proposed method enabled the reliable determination of ondansetron in bioequivalence studies after per os administration of a 4 or 8 mg tablet. © 2006 Elsevier B.V. All rights reserved.

A semi-automated liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the determination of glimepiride in human plasma. The plasma samples were treated by liquid-liquid extraction (LLE) in 1.2 mL 96-well format micro-tubes. Glimepiride and the internal standard (IS) glibenclamide were extracted from human plasma by LLE, using a mixture of ethyl acetate/diethyl ether 50:50 (v/v) as the organic solvent. After vortexing, centrifugation and freezing, the supernatant organic solvent was evaporated. The analyte and IS were dissolved in a small volume of a reconstitution solution, an aliquot of which was analyzed by reversed-phase LC/ MS/MS with positive ion electrospray ionization, using multiple reaction monitoring. The method proved to be sensitive and specific for both drugs, and statistical evaluation revealed excellent linearity for the range of concentrations 2.0-500.0 ng/mL with very good accuracy and inter- and intra-day precisions. The proposed method enabled the rapid and reliable determination of glimepiride in pharmacokinetic or bioequivalence studies after per os administration of a 3 or 4 mg tablet of glimepiride. Copyright © 2005 John Wiley & Sons, Ltd.

A rapid liquid chromatography/tandem mass spectrometry (LC/MS-MS) method was developed for the determination of lisinopril in human plasma. Lisinopril and the internal standard enalaprilat (IS) were extracted from human plasma by semi-automated solid phase extraction (SPE) using a 96-well format extraction plate. Initially, a 1:1 plasma: acetonitrile (ACN) mixture was prepared and vortexed to achieve protein precipitation. After centrifugation, an aliquot of the supernatant water/ACN solvent mixture was evaporated. The residue was dissolved in a certain volume of a reconstitution solution, which was passed through the extraction plate and the eluent was analyzed by combined reversed phase liquid chromatography tandem mass spectrometry with positive ion electrospray ionization using multiple reactions monitoring (MRM). The method was proved to be sensitive and specific for both drugs and its statistical evaluation revealed excellent linearity for the range of concentrations 2.0-200.0 ng mL-1 and very good accuracy, and inter- and intraday precisions. The proposed method enables the rapid and reliable determination of lisinopril in pharmacokinetic or bioequivalence studies after per os administration of 20 mg tablet formulations of lisinopril and it was applied in such study from our laboratory. © 2005 Elsevier B.V. All rights reserved.