Development of a novel 96-well format for liquid-liquid microextraction and its application in the HPLC analysis of biological samples

A novel 96-well liquid-liquid microextraction system combined with modern HPLC was developed and used for the simultaneous analysis of 96 biological samples. The system made use of hollow fibers, a 96-well plate, and a plastic base with a center hole and a side hole. One end of the hollow fiber was sealed, while the other end was attached to one of the holes positioned at the center for the plastic base. The needle was inserted into the liquid from inside or outside of the hollow fiber through the center or the side holes, respectively. The system was tested with plasma samples containing three compounds, acidic indomethacin, neutral dexamethasone, and basic propafenone. Some parameters, such as the kind and dimension of hollow fiber, pH and salt concentration of the donor phase, the selection of organic solvent for the acceptor phase, and the extraction time were investigated. Under the optimization conditions, the Log D and drug concentration of indomethacin, dexamethasone, and propafenone in plasma and urine samples were analyzed. Then, the methodology was validated. The results demonstrated that ng/mL levels could be exactly and rapidly analyzed by our system, which was equipped with an auto-injection sampler, making sample analysis more convenient.