Nageswara Rao Pilli

In the present paper, the authors described a novel Liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the determination of montelukast in human plasma using montelukast d6 as internal standard (IS). After solid phase extraction (SPE), the analyte and the IS were chromatographed on a C18 columns using a isocratic mobile phase composed of acetonitrile–5mM ammonium acetate (80:20, v/v) pumped at a flow rate of 0.8mL/min. The proposed method was validated in the range of 5.01–599.91 ng/mL as per the US FDA guidelines. Precision and accuracy results were calculated using five successful calibration curves. Analyte stability in true samples and in plasma samples under different conditions were established and results met the acceptance criteria. The chromatographic run time was set at 3 min, which makes the proposed method is high through put. The method was successfully applied to a pharmacokinetic study in healthy South Indian male subjects under fasting condition.

The authors proposed a simple, rapid and sensitive liquid chromatography / tandem mass spectrometry assay method for the determination of nateglinide in human plasma using carbamazepine as internal standard (IS). Analyte and the IS were extracted from the human plasma via liquid-liquid extraction using ethyl acetate. The chromatographic separation was achieved on a C18 column by using a mixture of 0.1% formic acid buffer –acetonitrile buffer (20:80, v/v) as the mobile phase at a flow rate of 0.8 mL/min. The calibration curve obtained was linear (r2 ³ 0.99) over the concentration range of 10.0–10005 ng/mL. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The proposed method was found to be applicable to pharmacokinetic studies.

This paper describes a simple, rapid and sensitive bioanalytical method based on liquid chromatography / tandem mass spectrometry (LC–MS/MS) for the determination of integrase inhibitor raltegravir in human plasma samples. Carbamazepine was used as an internal standard (IS). Analyte and the internal standard were extracted from 200 µL of human plasma via solid phase extraction. The chromatographic separation was achieved on a C18 column by using a mixture of acetonitrile and 0.1% formic acid (90:10, v/v) as the mobile phase at a flow rate of 0.8 mL/min. The calibration curve obtained was linear (r2 ³ 0.99) over the concentration range of 20.1–4007 ng/mL. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. A run time of 2.0 min for each sample made it possible to analyze more number of samples in short time, thus increasing the productivity. The proposed method was found to be applicable to pharmacokinetic studies in humans.

A simple and rapid liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and validated for simultaneous quantification of two protease inhibitors ritonavir and atazanavir in human plasma. Saquinavir was used as an internal standard. The analytes were extracted from human plasma samples by solid-phase extraction technique using a Orpheus C18 extraction cartridges. The reconstituted samples were chromatographed on a C18 column by using a 85:15 (v/v) mixture of methanol and 5mM ammonium acetate as the mobile phase at a flow rate of 0.9 mL/min. The calibration curves obtained were linear (r ³ 0.99) over the concentration range of 8.0-1600.0 ng/mL for ritonavir and 50.5-5995.2 ng/mL for atazanavir. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. A run time of 2.0 min for each sample made it possible to analyze more than 300 plasma samples per day. The proposed method was found to be applicable to clinical studies.

  A rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and fully validated for simultaneous quantification of two lipid lowering agents rosuvastatin and fenofibric acid in human plasma. Lovastatin was used as an internal standard. Analytes and the internal standard were extracted from human plasma by liquid-liquid extraction technique using a 50:50, v/v mixture of ethyl acetate and diethyl ether. The reconstituted samples were chromatographed on a C18 column by using a 80:20, v/v mixture of acetonitrile and 0.1% formic acid as the mobile phase at a flow rate of 1.0 mL/min. The calibration curve obtained was linear (r2 ³ 0.99) over the concentration range of 0.10-80.00 ng/mL for rosuvastatin and 50-9003 ng/mL for fenofibric acid. The multiple reaction monitoring mode was used for quantification of ion transitions at m/z 482/258, 319/233 and 405/199 for the rosuvastatin, fenofibric acid and the internal standard, respectively. The results of the intra-day and inter-day precision and accuracy study results were well within the acceptable limits. A run time of 3.0 min for each sample made it possible to analyze more than 300 plasma samples per day. The proposed method was successfully applied for the determination of the fenofibric acid in real time plasma samples for pharmacokinetic studies. Key words: Rosuvastatin, Fenofibric acid, human plasma, LC-MS/MS quantification, Pharmacokinetics.