Determination of ranolazine in human plasma by liquid chromatographic-tandem mass spectrometric assay

A highly sensitive liquid chromatographic-tandem mass spectrometric method (LC-MS-MS) is developed to quantitate ranolazine in human plasma. The analyte and internal standard tramadol are extracted from plasma by liquid-liquid extraction using diethyl ether-dichloromethane (60:40 v/v), and separated on a Zorbax extend C(18) column using methanol-10mM ammonium acetate (60:40 v/v, pH 4.0) at a flow of 1.0 mL/min. Detection is carried out by multiple reaction monitoring on a QtrapTM LC-MS-MS system with an electrospray ionization interface. The assay is linear over the range 10-5000 ng/mL with a limit of quantitation of 10 ng/mL and a lower limit of detection (S/N > 3) of 1 ng/mL. Intra- and inter-day precision are < 3.1% and < 2.8%, respectively, and the accuracy is in the range 96.7-101.6%. The validated method is successfully used to analyze the drug in samples of human plasma for pharmacokinetic studies.