Determination of Required Hydrophilic-Lipophilic Balance (RHLB) of Oleic Acid-Rich Vegetable Oil as Internal Phase of O/W Emulsion

Olive oil (OO) and avocado oil (AO) are rich in oleic acid, exhibiting health benefits that may help prevent several degenerative diseases. For oral administration, the oils need to be formulated as an emulsion in which the oil’s required hydrophilic-lipophilic balance (RHLB) is valuable data needed by the drug product formulator as the basis of surfactant hydrophilic lipophilic balance (HLB) selection. This research aimed to determine the RHLB of oils for oil-in-water emulsions using sorbitan-based surfactants. Ten emulsions were prepared comprising oil, surfactants, and water in the concentrations of 10%, 10%, and 80%, respectively. Tween 80 and Span 80 were varied to produce surfactant mixtures exhibiting an HLB range of 4.3 to 15. The height and transmittance at 800 nm (T) of the remaining emulsion after creaming were evaluated at 10 and 17 days of storage for AO and OO, respectively, which were used to calculate two stability parameters of RHLB determination, namely, percent height of remaining emulsion to the initial height (ESI) and 1/T. The curve of the parameters as a function of surfactant HLB shows the highest parameter, indicating maximum emulsion stability. The RHLB of oil is equivalent to the surfactant HLB that produces maximum stability, which was calculated using two mathematical approaches. Based on ESI and 1/T, the RHLB of OO were 11.02 and 11.11, while those for AO were 11.45 and 10.79, respectively. It is concluded that the RHLB of OO and AO are the same, i.e., 11.1.