UPLC-MS/MS determination of doxazosine in human plasma

A sensitive, selective and rapid method for the analysis of doxazosine (DOX) in human plasma based on ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) is described. DOX and tamsulosin, used as an internal standard (IS), were extracted by liquid-liquid extraction, and the chromatography was performed on a C18 UPLC column packed with 1.7 mu m particles. The total run time was 2 min. Detection was achieved by the multiple reaction monitoring of the following transitions: m/z 452 -> 344 and m/z 409 -> 228 for DOX and IS, respectively. Transitions of m/z 452 -> 247 and m/z 409 -> 271 were also collected for confirmation purposes. The calibration curve based on peak area ratio was linear up to at least 100 ng ml(-1), with a detection limit of 0.02 ng ml(-1) (a signal-to-noise ratio of 3). The method showed satisfactory reproducibility, and the short-term stability of the analyte was assessed. The method was successfully applied to the analysis of DOX in human plasma.