Bioanalytical LC-MS/MS method for simultaneous estimation of atorvastatin, its major active metabolites and ezetimibe.

Background: Hyperlipidemia is one of the most common chronic diseases encountered globally, and atorvastatin (ATV) is mainly metabolized into two major active metabolites. Methodology: Hence, we aimed to estimate ATV and ezetimibe (EZE) simultaneously in the presence of ATV major and active metabolites using a validated LC-MS/MS method. Conclusion: The proposed method was linear (r2 >0.99), accurate (92.02-109.94%) and precise (CV% ≤14) over the concentration range of 0.50-120 ng/ml, 0.20-48 ng/ml, 0.50-120 ng/ml and 0.20-48 ng/ml for ATV, EZE, 2-hydroxy ATV and 4-hydroxy ATV, respectively. The applied liquid-liquid extraction gave rise to reliable extraction recoveries of 84.91 ± 1.14%, 85.20 ± 1.62%, 85.46 ± 0.41% and 105.46 ± 2.35% for ATV, EZE, 2-hydroxy ATV and 4-hydroxy ATV, respectively.

LC-MS/MS bioassay of four proton pump inhibitors.

A new validated bio-analytical LC-MS/MS method was developed for the simultaneous extraction and determination of four proton pump inhibitors: esomeprazole, lansoprazole, pantoprazole and rabeprazole in human plasma using escitalopram as an internal standard. The proteins in plasma samples were precipitated using acetonitrile for the extraction of analytes which is a simple economic method. The separation was accomplished using a mobile phase composed of 10 mM ammonium formate: acetonitrile: methanol (20:40:40% v/v) at a flow rate of 0.8 mL/min in isocratic mode on a reversed phase C18 INERTSIL ODS-3 (5 µm, 150 × 4.6 mm) and column temperature of 40 °C. Positive mode electrospray ionization source was used prior to multiple reaction monitoring (MRM) detection using parent and daughter ions: m/z 346.2 → 198.1 for esomeprazole, m/z 370.1 → 252 for lansoprazole, m/z 384.2 → 200.2 for pantoprazole, m/z 360.1 → 242.1 for rabeprazole and m/z 325.2 → 109 for escitalopram. The calibration curves were constructed, and the method was linear in the range of 20-5000 ng/mL applying weighted (1/X2) linear regression coefficient for all drugs. The method was fully validated following US-FDA and EMA guidelines.