Upon sample illumination with a laser, droplets scatters light in all directions. Photon correlation spectroscopy measures droplets’ Brownian motion and correlates to the droplets’ size ( Rahman et al., 2011 Kathe et al., 2014). The most commonly used techniques for determination of droplet size upon SEDDS dilution with water are photon correlation spectroscopy or dynamic light scattering, laser diffraction, and coulter counting. Additionally, chain length of the TG in the oil phase of SEDDS can also affect emulsion droplet size, wherein using of TG with shorter chain length results in generation of the emulsion with lower droplet size ( Atef and Belmonte, 2008). Therefore, differences in chemical structure and chain length can predominantly determine emulsification efficiency and droplet size of the produced emulsion. (2015) obtained SNEDDS formulations which generate nanoemulsions with droplet size below 50 nm, if Tween 80 was used as a surfactant and above 100 nm, if Cremophor EL was used, although both surfactant exhibit similar HLB values. (2014) showed that increasing the proportion of higher HLB surfactant (Tween 80) in respect to lower HLB surfactant (Labrasol), results in decreasing the droplet size from 139 to 40 nm, due to greater reduction of the interfacial energy and better emulsification caused by higher HLB surfactant.
(2014) showed that increasing the proportion of oil component and decreasing the surfactant proportion results in increasing the droplet size. It has been reported that increasing the surfactant/cosurfactant ratio results in decreasing of the droplet size, as surfactants stabilize and condense interfacial film, while cosurfactant causes expansion of the film ( Kadu et al., 2011). Droplet size of the micro- or nanoemulsion generated after SEDDS dilution can be tuned by choosing suitable constituents and their concentration. Svetlana Ibrić, in Lipid Nanocarriers for Drug Targeting, 2018 12.3.2 Droplet Size Analysisĭroplet size is an important parameter in assessment of SEDDS, since it influences lipolysis process, drug release, and consequently absorption.