FACILE SYNTHESIS OF TITANIUM PHOSPHATES 155 COSMETIC PROPERTIES OF SYNTHESIZED TPS UV -Vis DRS (Figure 4) were obtained t o assess the optical property of synthesized sam- ples of TPs and to compare with PG-TiO2 and Degussa P25. The degree of diffuse refl ec- tance is dependent on parameters such as the refractive index, band gap, shape, and particle size of the material. A higher refractive index of 2.6 for TiO2 (30) favors higher light scattering properties than TPs, which has a lower refractive index below 1.8 (31). Therefore, Degussa P25 (Figure 4C) and PG-TiO2 (Figure 4D) show comparatively higher diffuse refl ectance than TPs (Figure 4A and B). PG-TiO2 having particle diameter 50 nm exhibit lower diffuse refl ectance than Degussa P25. The pigment materials used in cosmetic pr oducts having a lower photoactivity is an added advantage to minimize a certain degree of sebum breakdown on the skin (6,7). Titanium dioxide, the white pigment used in cosmetics is a powerful photoactive mate- rial capable of degrading wide variety of organic substances via rapid photochemical reac- tions in hydrated environments (32–34). Therefore, photoactivity of the synthesized TOP and TP were tested and compared with both PG-TiO2 and Degussa P25. Photo- induced abstraction of hydrogen atoms from hydrocarbons by DPPH can be assisted by the presence of semiconductor materials such as TiO2 (35,36). Photo-induced fading of DPPH from purple to pale yellow was followed by a rapid decrease in the absorption at 520 nm (see Figure 5B). The photoactivities of TP, TOP, PG-TiO2, and Degussa 25 were compared by measuring the decrease in absorption intensity at 520 nm for a period of 30 min of the analyte containing DPPH mixture and a test material. Gradual decrease in the Figure 4. UV - Vis DRS of (A) TOP, (B) TP, (C) P25, and (D) PG-TiO2.

JOURNAL OF COSMETIC SCIENCE 156 peak intensity at 520 nm recorded as a function of time is shown in Figure 5A. Samples show a 50% drop of the intensity at 28, 13, 11, and 4 min, respectively, for TP, TOP, PG-TiO2, and Degussa P25. Results clearly indicate that synthesized TP and TOP are fairly photoinactive when compared with TiO2. WR ability is another signifi cant paramet er in cosmetic products and urea is commonly used as an additive to maintain the moisture level on the skin and for the smoothness (37). Therefore, WR capacities of both TOP and TP samples with 5% w/w urea were tested after moisturizing at 57% RH (Figure 6A and B) (18). PG-TiO2 and Degussa P25 TiO2 were used as controls (Figure 6C and D). For TOP, PG-TiO2, and Degussa P25 TiO2, WR capacities rapidly declined to a 15–20% level because of the evaporation of loosely bound water from the surface in the fi rst 5 h. Subsequently, it remained relatively constant for the next tested time period. Interestingly, TP indicates a drop of WR to ~35% at 5 h and thereafter shows a slow water release rate. After 7 h, it shows about ~30% WR capacity, a higher value than TOP and control TiO2 samples. This indi- cates a good WR ability for the synthesized TP, which is better than the commercially available TiO2. CONCLUSIONS Two potential replacements fo r PG-TiO2 in cosmetic products, TOP and TP, were syn- thesized using ilmenite obtained from mineral sand as the starting material through H3PO4 digestion. The synthesized TOP and TP white pigments demonstrate signifi - cantly less photoactivity than PG-TiO2, implying a reduced risk of sebum breakdown on human skin. The WR capacities of moisturized pastes prepared with powdered materials, TOP, TP, and TiO2 with 5% urea, were measured. The synthesized TP shows a better WR capacity than TOP and PG-TiO2. As a potential next step in this research, safety data would be needed to generate to be used as a permitted colorant in the cosmetics industry. Figure 5. (A) Effect of UV irradiation on DPPH absorption at 520 nm with (i) no catalyst, (ii) TP, (iii) TOP, (iv) PG-TiO2, and (v) Degussa P25 dispersions. (B) UV-Vis absorption spectra of the DPPH• radical (i) and (ii-iii) the reduced form of the DPPH2.