Rapid determination of entrapment efficiency of liposomes by solid phase extraction-fluorospectrophotometry

The objective of this study was to establish a method for the determination of the entrapment efficiency of liposomes by solid phase extraction-fluorospectrophotometry.Paclitaxel was selected as the model drug.SampliQ C₁₈ solid phase extraction columns were applied to separate free paclitaxel and its liposome using water and 75% methanol solution as elute solutions,respectively.A fluorospectrophotometries method (λ_ex=244 nm,λ_em=311 nm) was applied to determine the entrapment efficiency of paclitaxel liposome.The calibration curve was linear in the range of 0.006-0.078 mg/mL(r=0.998),and the recoveries of blank liposome and free paclitaxel were all above 97.5%.The entrapment efficiency of paclitaxel liposome determined by this method was 50.8%（RAD=1.5%）,which has no significant difference from those results measured by mini-column centrifugation.Solid phase extraction-fluorospectrophotometry could be applied to determine the entrapment efficiency of paclitaxel liposome rapidly and accurately and could be used to control the quality of paclitaxel liposome.