Sensitive method for the determination of ibutilide in human plasma by liquid chromatography-tandem mass spectrometry

A rapid, selective and sensitive liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed and validated for determination of ibutilide in human plasma. The analyte and internal standard sotalol were extracted from plasma samples by liquid-liquid extraction, and separated on a C(18) column, using acetonitrile-water-10% butylamine-10% acetic acid (80:20:0.07:0.06, v/v/v/v) as the mobile phase. Detection was performed on a triple-quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via TurboIonSpray ionization (ESI). Linear calibration curves were obtained in the concentration range of 20-10,000 pg/ml, with a lower limit of quantitation of 10 pg/ml. The intra- and inter-day precision values were below 8% and accuracy was within +/-3% at all three QC levels. The method was utilized to support clinical pharmacokinetic studies of ibutilide in healthy volunteers following intravenous administration.