Pre-Equilibrium Solid-Phase Microextraction of Free Analyte in Complex Samples: Correction for Mass Transfer Variation from Protein Binding and Matrix Tortuosity

摘要

The accurate measurement of free analyte concentrationsnwithin complex sample matrixes by pre-equilibriumnsolid-phase microextraction (SPME) has proven challengingndue to variations in mass uptake kinetics. For the first time, theneffects of the sample binding matrix and tortuosity on thenkinetics of analyte extraction (from the sample to the SPMEnfiber) are demonstrated to be quantitatively symmetrical withnthose of the desorption of preloaded deuterated standardsn(from the fiber to the sample matrix). Consequently, kineticncalibration methods can be employed to correct for variation innSPME sampling kinetics, facilitating the application of preequilibriumnSPME within complex sample systems. This approachnwas applied ex vivo to measure pharmaceuticals in fishnmuscle tissues, with results consistent with those obtained fromnequilibrium SPME and microdialysis. The developed methodnhas the inherent advantages of being more accurate, precise, and reproducible, thus providing the framework for applications wherenrapid measurement of free analyte concentrations (within complicated sample matrixes such as biological tissues, sediment, andnsurface water) are required.