Determination of amlodipine in human plasma using automated online solid-phase extraction HPLC-tandem mass spectrometry: application to a bioequivalence study of Chinese volunteers.

An automated method (XLC-MS/MS) that uses online solid-phase extraction coupled with HPLC-tandem mass spectrometry was reported here for the first time to quantify amlodipine in human plasma. Automated pre-purification of plasma was performed using 10 mm × 2 mm HySphere C8 EC-SE online solid-phase extraction cartridges. After being eluted from the cartridge, the analyte and the internal standard were separated by HPLC and detected by tandem mass spectrometry. Mass spectrometric detection was achieved in the multiple reaction monitoring mode using a quadrupole tandem mass spectrometer in the positive electrospray ionization mode. The XLC-MS/MS method was validated and yielded excellent specificity. The calibration curve ranged from 0.10 to 10.22 ng/mL, and both the intra- and inter-day precision and accuracy values were within 8%. This method proved to be less laborious and was faster per analysis (high-throughput) than offline sample preparation methods. This method has been successfully applied in clinical pharmacokinetic and bioequivalence analyses.