Simultaneous estimation of atorvastatin and its two metabolites from human plasma by ESI-LC-MS/MS.

A selective, sensitive, and fast high performance liquid chromatography (HPLC) method with mass spectrometric (MS) detection mode has been developed and validated completely in human plasma. Atorvastatin (ATO), p-hydroxy atorvastatin (p-HATO), o-hydroxy atorvastatin (o-HATO) and internal standard (IS) are extracted from human plasma via solid phase extraction (SPE) technique. After elution, the solution is evaporated, then reconstituted with 250 µL of Mobile Phase and analyzed using HPLC/MS/MS system. An isocratic mode is used to separate interference peaks using a Symmetry C-18, 75 × 4.6 mm ID, 3.5 µ, column. The m/z of ATO, o-HATO and p-HATO are 559.2/440.2, 575.3/440.4 and 575.0/440.4 respectively. Linearity ranges are 0.05 to 252.92 ng/mL for ATO, p-HATO and o-HATO respectively. Calibration functions, lower limit of quantitation (LLOQ), stability, intra- and inter-day reproducibility, accuracy, and recovery are estimated. This method is free from matrix effects and any abnormal ionization. This method was successfully applied to a single dose 80 mg tablet bioequivalence (BE) study of Atorvastatin.