There is no doubt that the field of artificial membrane transport using
synthetic ionophores has advanced remarkably in the past 15 years due
primarily to the synthesis of new ionophores. Even though the
theoretical framework substantially predated this activity, the merging
of theory with transport experiment has often been sketchy. The purpose
of this outline has been to examine key examples to illustrate the
underlying principles and to suggest how experimental variables dominate
the results obtained. To a very good approximation the assumption of a
"diffusion" regime is often justified, is easily confirmed
experimentally and provides a clear framework for exploitation of the
inherent selectivity of a given ionophore. Thus for synthetic chemists
who wish a "quick and nasty" experiment to examine the question of
selectivity, the recipe is clear: a mixture containing all ions of
interest in a standard experiment for each ligand of interest using a
moderately stirred (100-200 rpm) cell and analysis of the mixture
produced on the OUT side of the cell at a fixed, small extent of
transport. Together with duplicates and controls, this modest set of
experiments will place the results on an unambiguous footing from which
clear conclusions about each ionophore's characteristics are readily
obtained. For those with more detailed interests in the transport
process the demands are correspondingly higher.