Methods and issues in microdialysis calibration

A review of calibration in microdialysis is presented. This review covers the methodological aspects of microdialysis including how physico-chemical parameters such as analyte diffusion coefficient, kinetics, volumetric flow rates, and membrane length affect calibration. The effects of diffusion versus diffusion coupled with chemical reaction are discussed in relationship to microdialysis extraction fraction and calibration. Resistance theory is used throughout to illustrate how diffusion and chemical reaction affect microdialysis calibration. In vivo calibration methods such as mass transfer coefficient, no-net flux method (Lonnroth method), internal standards (retrodialysis), in vivo delivery, and slow perfusion method are discussed. Applications of these various in vivo calibration methods are also included. Mathematical models are presented as a means to help understand the physical parameters that affect microdialysis calibration. Finally, the challenges in interpreting results from transient methods such as trapping free radicals and in situ metabolism are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.