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The authors developed a novel, sensitive high-throughput ultra-performance liquid chromatography-tandem mass spectrometric method for the determination of dofetilide in human plasma. To compensate for the matrix effect, a deuterated internal standard was used. The method employed a very low sample volume (50 μL) of plasma for sample processing by using simple protein precipitation extraction in a 96-well plate. The extracted samples were chromatographed on an Acquity BEH C18 column (2.1 × 100 mm, 1.7 μm) and eluted in a gradient manner at a flow rate of 0.5 mL/min for 2 min using 5 mM ammonium formate (0.1% formic acid) and methanol. The calibration curve was linear from 25 to 2,500 pg/mL with a correlation coefficient (r2)  ≥ 0.99 (0.9969–0.9980; n  = 3). The developed method was validated as per the current United States Food and Drug Administration's guidance for industry on 'Bioanalytical Method Validation'. The multiple reaction–monitoring mode was employed for quantitation of dofetilide with m/z 442.2/198.2 and dofetilide d4 with m/z 446.2/198.2. The validated method was used for evaluation of dofetilide concentration in the Comprehensive in vitro Proarrhythmia Assay phase 1 electrocardiogramic biomarker validation study. [ABSTRACT FROM AUTHOR]

In mass spectrometry, compounds that have different ionization properties experience challenges in simultaneous analysis. In the present paper, the authors proposed a polarity switching (+ve and -ve) LC-MS/MS method to analyze oxycodone and topiramate in a single run. The developed method was validated in the range of 5–1000 ng/mL for oxycodone and 20–5000 ng/mL for topiramate as per the US FDA guidelines. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode to analyze oxycodone and topiramate simultaneously using oxycodone-d 6 and topiramate-d 12 as internal standards, respectively. Sample preparation was performed in 96-well protein precipitation plates using acetonitrile. Processed samples were analyzed using a C 18 column with a gradient mobile phase composed of 10 mm ammonium formate with 0.1% formic acid and acetonitrile. The method was validated for selectivity, specificity, linearity, precision and accuracy, dilution integrity and stability. After validation, this method was successfully applied to quantify oxycodone and topiramate in plasma of concomitantly treated Sprague Dawley (SD) rats. • Polarity switching to detect and quantify analytes with different polarities. • High-throughput sample processing using 96-well plate format. • Application to pharmacokinetic interaction study. [ABSTRACT FROM AUTHOR]