The pH-Stat method represents an extension of the Ussing chamber technique. Using this method, it is possible to simultaneously monitor fluxes of protons (acids) or basic equivalents.
With the help of this method it is possible to determine in which form ammonia is absorbed across a piece of ruminal epithelium. If the efflux occurs in the form of NH₃, no change in potential should be observed and an alkalinization should occur. After efflux of NH₄⁺, a change in current and voltage and a discrete acidification should occur. Of course, both may simultaneously occur – so that pH remains the same, but a change in current and potential is observed!
As a rule, it will be necessary to carry out many different investigations using various methods to determine via what pathway a substance is absorbed.