Sure, you can also work with a trial-and-error method but, building a phase diagram will give you the limits of the Winsor IV (one phase) domain. On the whole, the surfactant amount required for a microemulsion is much higher than for an emulsion, say, ca. 10 wt.% or a surfactant-to-oil ratio higher than 1, but it also depends whether or not you add a cosolvent or co-surfactant. See, for instance J. McClements' works.

Thanks for the information. However, I'm sure trial and error takes much longer time and constructing a phase diagram is more feasible.

Dear Poonam Singha,

you may look into this.

www.stevenabbott.co.uk/HLD-NAC.html

Sure, J. McClements' works are a good guide to fabricate and optimize micro/ nanoemulsions. Besides, I believe that pseudo-ternary phase diagrams help to fine tune the formulation components of micro-emulsion in a quicker way.

You could also read the recent review by J.L. Salager and coworkers in the latest issue of the Journal of Surfactants and Detergents.

Thank you for the references

there a several aspects when considering optimization of a microemulsion. From a pharmaceutical point of view, the biocompatibility of the formulation, the release rate of the drug, the pH, viscosity etc. may be referred. So, first you need to define the behavior you want your microemulsion to possess. Afterwards, you can find the optimum ratio between components by evaluating one or more parameters for that system (like viscosity, interfacial or superficial tension, pH and so on). 

Hello Singha,

I am currently working a lot on micro and nanoemulsion. I tell you 2 ways, both are easy.1. take all components together (oil:water=1:1, surfactant (5-6%wt), add salt (.5%), measure conductivity with temperature. The lowest value will tell you the phase inversion. Now keep that temperature and increase surfactant concentration untill an isotropic phase is appeared. When you get it, just dilute with water and it will form nanoemulsion spontaneously.

2. If you dont have conductometer: Just take oil:water=1:1 and gradually add surfactant to get an isotropic phase. When you reach, just dilute with water and you will get nanoemulsion.

why you choose oil:water=1:1?

I took oil:water ratio 1:1 so that I could obtain a bicontinuous micro emulsion.

in general Bicontinuous microemulsion gives spontaneous emulsification. There are lot of artists available.