I am preparing a emulsifiable concentrate (EC) formulation for pesticidal activity; in which first one will be drug (oily substance), second one will be solvent and third one is surfactant. I have been trying many surfactants including anionic (Sodium lauryl sulphate, SLS) and nonionic surfactant (tween 20 and 80, span 20 and 80) but these are not showing stability in o/w type of emulsion. According to literature, mixture of anionic and nonionic surfactants is good to form stable emulsion but SLS in only soluble in water and not soluble with nonionic surfactant. How can i prepare stable emulsion, kindly suggest?