A SPE/HPLC/DAD method was developed for the in vivo monitoring of three new antileishmanial 2-substituted quinolines under study in our laboratory for the development of an oral treatment. Three phase I metabolites were included in this work for the optimization of the method. Trifunctional tC(18) cartridges (resulting from the reaction of trifunctional silanes with silica surface) were selected among four sorbents tested. Two linear gradients were developed to ensure resolution of metabolites. Recovery of quinolines from rat plasma was comprised between 80.6 and 88.2%. In a drug development perspective, apparent pK(a), lipophilicity and solubility were determined, as well as the extent of plasma protein or albumin binding.