For nano-emulsions prepared by the phase inversion temperature
method, optimization by selective variation parameters is
presented in several cited references of recent bibliography. In
[43,46] variation of droplet size is studied with respect to oil
surfactant ratio with the obvious result that the higher the oil surfactant ratio the greater the droplet size, and in [45] variation
of droplet size with surfactant mixing ratio is studied with the
remarkable result that droplet size does not depend on surfactant
mixing ratio if nano-emulsions are prepared by cooling from the
HLB temperature.
For nano-emulsions prepared by the phase inversion composition
method, there are also several studies in recent bibliography.
In [54] optimization with respect to preparation
method and variation of droplet size with oil surfactant ratio are
presented. In [49] different routes for emulsification are studied
and droplet size variation with HLB, water fraction and surfactant
concentration is also reported. In Ref. [55], effect of
variables HLB and oil surfactant ratio are separately studied with
the expected result that there is an optimum HLB and that the
higher the oil surfactant ratio the greater the droplet size. In Ref.
[56] optimization of W/O nano-emulsion preparation is presented.
For different combinations of Span-Tween surfactants,
an optimum surfactant composition presenting a water solubility
maximum is chosen, and droplet size variation is studied with
respect to water concentration. Also with W/O nano-emulsions,
the result is, as expected and coinciding with Ref. [47], that the
higher the water concentration the greater the droplet size.
For nano-emulsions prepared by self-emulsification, there is
a detailed work on optimization [57]. Droplet size variation
with oil, surfactant HLB, and solvents, was studied. The results
indicated that there are optimum values for HLB and proportions
of solvents.
As an example of optimization of nano-emulsion function, in
Ref. [26] the influence of sucrose surfactants on percutaneous
penetration is studied, and in Ref. [35] the efficacy of a
schistosomicidal agent is improved by incorporating the agent
in nano-emulsions.