DETERMINATION OF REQUIRED HLB VALUE 413 M ETHODS P REPARATION OF EMULSIONS T he volume of the O /W emulsion prepared was 50 mL and contained 1 wt% surfactant, 3 wt% of essential oils or HF, and 96 wt% pure water. The surfactants, sorbitan sesquio- leate (HLB = 3.70) and polysorbate 60 (HLB = 14.90), comprised 1 wt% of the total blend concentration used in the O /W emulsions. A series of emulsions with HLB values were prepared by blending the emulsifi ers together in different ratios (1). We can calcu- late the HLB of the mixed surfactants using the following formula (12,14): PL[ WRWDO +/% +/% D D E E & & & q q+/% where Ca and Cb are the quantities of surfactants (%) an d HLBa and HLBb are the HLB values of surfactants. Af ter mixing the surfactant with essential oil, the mixture was kept for 2 h at a tempera- ture control of 45°C in a screw cap bottle to prevent the essential oil from volatilization and was placed in an ultrasonic cleaner (JAC-3010, KODO, Seongnam, Korea) for 20 min and mixed well. After addition of purifi ed water, the solution was vortexed for 1 min using a vortex mixer (vortex genie-2, Scientifi c Industries Inc., Bohemia, NY), and then stored at room temperature for 1 week. X: Sorbitan sesquioleate (HLB = 3.70) + polysorbate 60 (HLB = 14.90), Y: Sorbitan ses- quioleate (HLB = 3.70) + polysorbate 20 (HLB = 16.70), Z: Polysorbate 60 (HLB = 14.90) + polysorbate 20 (HLB = 16.70) Table II Main Composition Content for Two Citrus unshiu Oils INCI name Main composition content (%)a Citrus unshiu fruit oil dl-Limonene (92.51), gamma-Terpinene (0.68), alpha-Pinene (0.53) Citrus unshiu peel oil dl-Limonene (91.97), gamma-Terpinene (3.48), alpha-Pinene (0.69) a Gas chromatograph mass spectrometer (GCMS-QP2010 plus, Shimadzu, Japan). INCI, International Nomenclature Cosmetic Ingredient.

JOURNAL OF COSMETIC SCIENCE 414 UV- VIS SPECTROPHOTOMETER MEASUREMENTS The O /W emulsions shown previously were used for UV-vis measurements (2,4,6,15). Turbid- ity was compared using a UV-vis spectrophotometer (OPTIZEN Alpha, KLAB, Daejeon, Korea). For measurements, 1 mL of each CUFO and CUPO were used and diluted with 15 mL of purifi ed water. Likewise, 1 mL of CJSO was diluted with 10 mL of purifi ed water, and 1 mL HF was diluted with 15 mL of purifi ed water. All measurements were carried out at 600 nm. Turbidity was measured using the following equation (1,4,15): 7XUELGLW\ 7 $ ORJ7 w here T is transmittance and A is absorbance. The measurements were performed in triplicate. TURB IDITY METER MEASUREMENT Turb idity was compared using a turbidity meter (TU-2016, Lutron, Taipei, Taiwan). Turbidities of the essential oils or the HF emulsions were measured with the turbidity meter (Lutron) after 1 week storage at room temperature (2–4). Turbidity by nephelometry as ntu (nephelometry turbidity unit) was measured by diluting with purifi ed water [CUFO emulsion 30% (v/v), CUPO and CJSO emulsions 50% (v/v), and HF emulsion 60% (v/v)]. Measurements were performed in triplicate. DROP LET SIZE ANALYSIS Oil droplet sizes of the O /W emulsions were determined by dynamic light scattering using a Nano Zeta sizer (Nano ZS, Malvern Panalytical, England). Tubes with the O /W emulsions were stored undisturbed at room temperature. On the seventh day, each emulsion was diluted using pure water (1:100). Measurements were performed in trip- licate, and the average droplet size was expressed by using the mean droplet diameter. RESU LTS AND DISCUSSION MACR OSCOPIC APPEARANCE OF THE EMULSIONS Appe arance of the O /W emulsion [surfactant X: sorbitan sesquioleate (HLB = 3.70) + poly- sorbate 60 (HLB = 14.90)] was observed after storing for 1 week at room temperature. Figures 1, 4, and 5 show that the lower the HLB value, the more the upper part is separated. Figures 2 and 3 show that the highest turbidity when HLB had the highest value, 14.90. The comparison of the degree of emulsifi cation by suspension or layer separation is diffi cult for the HF (Figure 4) and CJSO (Figure 5) emulsions in the HLB from 5.94 to 12.66. TURB IDITY MEASUREMENT UV-v is spectrophotometer. The O /W emulsions stored at room temperature for 1 week were used in this experiment. The turbidity values for liquid paraffi n, CUFO, CUPO, HF, and CJSO emulsions at different HLB values are illustrated in Figures 6 and 7.