Parallel extraction columns and parallel analytical columns coupled with liquid chromatography/tandem mass spectrometry for on-line simultaneous quantification of a drug candidate and its six metabolites in dog plasma

A method with parallel extraction columns and parallel analytical columns ( PEC-PAC) for on-line high-flow liquid chromatography/tandem mass spectromet ry (LC/MS/MS) was developed and validated for simultaneous quantification o f a drug candidate and its six metabolites in dog plasma. Two on-line extra ction columns were used in parallel for sample extraction and two analytica l columns were used in parallel for separation and analysis. The plasma sam ples, after addition of an internal standard solution, were directly inject ed onto the PEC-PAC system for purification and analysis. This method allow ed the use of one of the extraction columns for analyte purification while the other was being equilibrated. Similarly, one of the analytical columns was employed to separate the analytes while the other was undergoing equili bration. Therefore, the time needed for reconditioning both extraction and analytical columns was not added to the total analysis time, which resulted in a shorter run time and higher throughput. Moreover, the on-line column extraction LC/MS/MS method made it possible to extract and analyze all seve n analytes simultaneously with good precision and accuracy despite their ch emical class diversity that included primary, secondary and tertiary amines , an alcohol, an aldehyde and a carboxylic acid. The method was validated w ith the standard curve ranging from 5.00 to 5000 ng/mL. The intra- and inte r-day precision was no more than 8% CV and the assay accuracy was between 9 5 and 107%. Copyright (C) 2001 John Wiley & Sons, Ltd.