Very accurate measurements of mass transfer can be made rapidly by permitting diffusion of an agent desired to be measured into or out of a small, very precisely known volume of a microdialysis probe, then rapidly pumping or flushing (“pulsing”) the probe with a known volume of fluid as a single pulse. The diffusion and pulsing may be repeated. The method, hereinafter called pulsatile microdialysis (PMD) to distinguish it from prior art continuous flow microdialysis, is useful for measurements in a number of processes, including protein binding, adsorption to binding agents such as activated charcoal, release from microemulsion drug delivery systems, determination of drug diffusion coefficients and concentrations, and for various other purposes.The method is based on mathematical manipulation of Ficks Laws. Resulting equations were verified against experimental data using methazolamide, warfarin and benzocaine as test drugs.
