Application of Sensitive, Rapid and Validated Liquid Chromatography Tandem Mass Spectrometry Method for Simultaneous Determination of Letrozole and Metformin in Human Plasma

A rapid and sensitive liquid chromatography tandem mass spectrometry method has been developed and validated for the simultaneous determination of metformin and letrozole in human plasma. The solid-phase extraction technique was used for the extraction of metformin and letrozole from human plasma. Anastrozole was used as the internal standard (IS). Chromatography was performed on a Hypurity C18, 5 μm, 50 mm × 4.6 mm column, with the mobile phase consisting of 5mM ammonium formate and acetonitrile (in a 20:80 ratio), followed by detection using mass spectrometry. The method involves a simple reversed isocratic chromatography condition and mass spectrometry detection, which enables detection at sub-nanogram levels. The method was validated and the lower limit of quantification for metformin and letrozole was found to be 5.0 ng mL−1and 0.5 ng mL respectively. The mean recovery for letrozole and metformin ranged from 90.1 to 95.6%. This method increased the sensitivity and selectivity; resulting in high-throughput analysis of letrozole and metformin using single IS in a single experiment for bioequivalence studies, with a chromatographic run time of 2.5 min only.