Comparison of liposome entrapment parameters by optical and atomic absorption spectrophotometry

Methods for the complete characterization of liposomes prepared by ether-injection are described in detail. The validity of atomic absorption spectrophotometry for measuring markers of trapped volume was checked by comparative determinations of markers with established optical spectrophotometrical methods. The favorable results using atomic absorption spectrophotometry to quantitate the marker Mn2+ are of particular relevance as manganese ion is also the paramagnetic probe in n.m.r. measurements of water permeability of liposomes; our results indicate that in such measurements no other marker need be incorporated.