A method for measuring or identifying a component of interest in a biological system is disclosed herein. The method includes positioning a fiber within the biological system, the fiber being at least partially coated with a polymeric extraction phase for adsorbing the component of interest from the biological system, the extraction phase being positioned within the biological system adsorbing the component of interest onto the extraction phase removing the fiber from the biological system inserting the fiber into a nanospray needle flowing solvent through the nanospray needle desorbing the component of interest from the extraction phase into the solvent and nanospraying the desorbed component of interest into an analytical instrument for measurement or identification.
