Hydrodynamic size characterization of a self-emulsifying lipid pharmaceutical excipient by Taylor dispersion analysis with fluorescent detection

In this work, the sizing of microemulsion droplets of a lipid-based pharmaceutical excipient (Labrasol® ALF) is performed by Taylor dispersion analysis (TDA) using fluorescent detection. An hydrophobic fluorescent marker is used to tag the microemulsion droplet and to increase the sensitivity of detection (compared to UV detection). Combined with the frontal TDA mode, fluorescent detection was mandatory for an accurate sizing of microemulsions containing large coacervates. Microemulsion sizing of Labrasol was performed at various concentrations from 1 to 70g.L−1 and at two different temperature (25°C and 37°C). Results obtained by TDA are compared to those derived from DLS measurements. The combination of both techniques allows estimating the size and proportion of coacervates in the microemulsion, as well as the polydispersity in size of the sample.