Determination of required hydrophilic-lipophilic balance of citronella oil and development of stable cream formulation.

Context: Citronella oil is reported to have excellent mosquito-repellent activity. To develop a stable cream formulation (emulsion), its hydrophilic-lipophilic balance (HLB) value is important.

Objective: To determine required hydrophilic-lipophilic balance (rHLB) value of citronella oil and to develop stable cream formulation.

Materials And Methods: Emulsions of citronella oil were prepared by phase inversion temperature technique using water, Tween 80 and Span 80. A first series of 11 emulsions with HLB values ranging from 5.0 to 15.0 and a second series of eight emulsions with smaller interval in HLB values from 11.0 to 13.8 were prepared. Emulsions were evaluated for creaming index, droplet size and turbidity to determine rHLB. Utilizing determined rHLB, citronella oil cream was formulated and evaluated for different texture parameters. rHLB of light liquid paraffin was also determined for validation of methodology.

Results: rHLB of light liquid paraffin and citronella oil was determined to be 11.80 and 12.60, respectively. Stable citronella oil cream was developed with 10% emulsifier blend. Texture parameters were found to be consistent over the entire storage period.

Discussion: Creaming index, droplet diameter, percent increase in droplet diameter and turbidity are the established parameters to determine rHLB and to develop stable emulsion. Emulsions with optimum emulsifier concentration resulted in less percentage creaming index, smallest droplet, less percentage increase in droplet diameter and highest turbidity. Texture properties evaluation ensures the stability of the developed cream.

Conclusion: rHLB value of citronella oil was found 12.6 and a stable cream was formulated utilizing determined rHLB.