Liquid chromatographic analysis of doxazosin in human serum with manual and robotic sample preparation

A specific method for the determination of the antihypertensive drug doxazosin in human serum is described. The method utilizes the related drug prazosin as an internal standard and is based on a simple extraction scheme followed by analysis by reversed-phase ion suppression high-performance liquid chromatography (HPLC) on an alumina-based column with fluorescence detection. The method is completely automated with a flexible robotic system for the analysis of drugs in biological fluids. The robotic automation of the method allows a 20% increase in the sample throughput and the savings of about 7 man-hours a day. Both the manual and robotic procedures yield precise quantitative results over the therapeutically relevant concentration range of 0.5 to 20 ng/mL of serum.