An isocratic liquid chromatography-electrospray ionization tandem mass spectrometric determination of varenicline in human plasma and dosage form

A simple, sensitive and accurate liquid chromatography tandem mass spectrometric (LC/MS/MS) method has been developed and validated for determination of varenicline (VRC) in human plasma and pharmaceutical tablets as a tool for therapeutic drug monitoring. The VRC and internal standard (paracetamol, IS) were extracted by liquid-liquid extraction technique. The separation was achieved on C18 column (150mm × 4.6 mm, 5 µm, maintained at 25°C) by isocratic mode at a flow rate of 0.7 ml/min using a mobile phase consisted of a mixture of 5 mM ammonium formate, pH 7.5 (A) and (acetonitrile: methanol, 50:50, v/v) (B) in a ratio of A:B (15:85, v/v) for 10 min. The analytes were monitored by electrospray ionization in positive ion multiple reaction monitoring (MRM) mode. Optimization of MRM mode and chromatogrphic conditions were applied to elmeinate the interference peaks and increse of sensitivity. The method was linear ( r 2 = 0.9998) at concentration range of 20.0 to 500.0 ng/ml with lower limit of detection of 6.0 ng/ml. The method was statistically validated for linearity, accuracy, precision and selectivity following Food and Drug Administration (FDA) guidelines. The mean extraction recovery of VRC from human plasma was 87.06 ± 2.47%. The reproducibility of the method was reliable with the intra- and inter-day precision was < 5% and average accuracy of 103.54%. The validated method was successfully applied to quantify VRC in human plasma as well as bulk and dosage form in quality control laboratory.