this invention improves the pampa method used in pharmaceutical , biotechnological , and agrochemical r & amp ; d . this new high - throughput method and apparatus for measurement of permeability and membrane retention of compounds overcomes shortcomings of prior art and includes sensitivity and speed enhancing reagents . the phospholipid membranes used here consist of 10 – 74 % wt / vol soybean lecithin extract dissolved in dodecane . concentrations are measured by direct uv spectroscopy . to reduce membrane retention , surfactants , cyclodextrins , or water - soluble lipophilic polymers with low uv absorption are used in the acceptor comparment of the permeation cells and create an artificial sink state . a ph gradient established between donor and acceptor solutions creates a secondary sink state . this “ double - sink ” makes successful modeling of passive - diffusion transport of molecules possible . by accelerating transport of certain molecules , it shortens measurement time and increases assay throughput . a new permeability equation accounts for the “ double - sink ” condition as well as membrane retention .