Development and validation of a highly sensitive and robust LC-MS/MS with electrospray ionization method for...

A high-throughput, simple, highly sensitive and specific LC-MS/MS method (liquid chromatography coupled with tandem mass spectrometry) has been developed for the estimation of rosuvastatin (CAS 287714-41-4, RST) with 100 microl human plasma using atorvastatin (CAS 134523-00-5) as an internal standard (IS). The API-4000 LC-MS/MS was operated under the multiple reaction-monitoring mode (MRM) using the electro spray ionization technique. The assay procedure involved direct precipitation of RST and IS from plasma with acetonitrile. Sample preparation with this method yielded clean extracts and consistent recoveries: 91.39% for RST and 99.28% for IS. The total chromatographic run time was 3.5 min and the elution of RST and IS occurred at 2.5 and 3.1 min, respectively; this was achieved with a mobile phase consisting of 0.05 mol/L formic acid: acetonitrile (20:80, v/v) at a flow rate of 0.50 ml/min on an Inertsil ODS-3 column (4.6 x 100 mm, 3.0 microm). The developed method was validated in human plasma with a limit of quantitation of 0.05 ng/ml. A linear response function was established for the range of concentrations of 0.05 to 50.0 ng/ml with a correlation coefficient (r) of 0.999. The inter- and intra-day precision in the measurement of RST quality control (QC) samples at 0.05, 0.15, 25 and 40 ng/ml were in the range of 6.55 to 11.40% relative standard deviation (RSD) and 1.76 to 11.17% RSD, respectively. Accuracy in the measurement of QC samples for RST was in the range of 95.02 to 101.37% of the nominal values. RST was stable in the battery of stability studies viz., bench-top, auto-sampler and freeze-thaw cycles. The stability of RST was established for 1 month at -80 degrees C. The application of the assay to a clinical study confirmed the utility of the assay to derive human pharmacokinetic parameters.