A rapid and most sensitive method for simultaneous determination of enalapril (ENP) and its metabolite, enalaprilat (ENPT), in human plasma using ESI-LC-MS/MS (electrospray ionization liquid chromatography tandem mass spectrometry) positive ion multiple reactions monitoring (MRM) mode, was developed and validated. The procedure involves a simple solid-phase extraction (SPE) followed by evaporation of the sample. Chromatographic separation was carried out on a Hypurity C(18) column (50 mm × 4.6 mm, 5 µm) with an isocratic mobile phase and a total run time of 2.0 min only. The MRM of ENP and ENPT is 377.10 → 234.20 and 349.20 → 206.10 respectively. The standard calibration curves showed excellent linearity within the range of 0.064 to 431.806 ng/mL for ENA and 0.064 to 431.720 ng/mL for ENPT (r ≥ 0.990). This is the only method which can quantitate upto 0.064 ng/mL for both ENP and ENPT in a single run with the shortest analysis time. In matrix effect experiment, this method shows a % CV (% coefficients of variation) of less than 5, which means that the proposed method is free from any kind of irregular ionization process. This method was successfully applied to a pharmacokinetic study after oral administration of enalapril maleate 20 mg tablet in Indian healthy male volunteers.

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. Copyright © 2011 John Wiley & Sons, Ltd.