QUANTITATION OF TITANIUM DIOXIDE 383 CONCLUSION In this research, we analyzed amounts of titanium dioxide in sunscreen cosmetics by employing a novel volumetric method based on redox titration. On the basis of the results of this study, we found that the method gives quantitatively accurate and reliable data with routine lab-ware and chemicals. REFERENCES (1) K. F. De Polo, A Short Textbook of Cosmetology, 1st ed. (Verlag for chemische Industrie, H. Ziolkowsky GmbH, Augsburg, Germany, 1998). (2) M. Caswell, Sunscreen formulation and testing, Cosmet. Toiletr., 116, 49-60 (2004). (3) J. Glowczyk-Zubek, Cosmetic application of microfine titanium dioxide,]. Appl. Cosmetol., 22, 74-76 (2004). (4) J. Ginestar, Pigments as photoprotectans, Cosmet. Toiletr., 118, 73-78 (2003). (5) K. Klein, Encyclopedia of UV absorbers for sunscreen products, Cosmet. Toiletr., 107, 45-50 (1992). (6) L. Rigano, A. Mezzanotte, M. Lohman, and L. Kujansivu, Hydrogenated polydecenes and high-SPF physical sunscreens, Cosmet. Toiletr., 117, 79-85 (2002). (7) A. Townshend, Encyclopedia of Analytical Science (Academic Press, London, 1995), vol. 9, pp. 5236- 5240. (8) H. Onishi, "Photometric Determination of Traces of Metals, Part IIB: Individual Metals, Magnesium to Zirconium," in Chemical Analysis, 4th ed. (John Wiley & Sons, New York, 1989), vol. 3, pp. 535-585. (9) J. C. Bailar, H.J. Emeleus, R. Nyholm, and A. F. Trotman-Dickenson, "Group IB, IIB, IIIA, IV A, VA VIA, VIIA, VIII," in Comprehensive Inorganic Chemistry (Pergamon Press, 1976), vol. 3, pp. 359-361. (10) F. D. Snell and L. S. Eltre, Encyclopedia of Industrial Chemical Analysis (Interscience Publishers, 1979), vol. 13, pp. 425-427.

J. Cosmet. Sci., 57, 385-395 (September/October 2006) Photostabilization of organic UV-absorbing and anti-oxidant cosmetic components in formulations containing micronized manganese-doped titanium oxide G. WAKEFIELD and J. STOTT, Oxonica Healthcare, 7 Begbroke Science Park, Sandy Lane, Yarnton, Oxford OX5 JPF, UK. Accepted for publication June 12, 2006. Synopsis Micronized titanium oxide (TiO2) and manganese-doped titanium oxide (TiO2:Mn) particles have been incorporated into a variety of oil-in-water (O/W) and water-in-oil-in-water (W/O/W) emulsions in con­ junction with the UV-absorbing organic compounds butyl methoxydibenzoylmethane (BMDM) and octyl methoxycinnamate (OMC) and with the anti-oxidants vitamin E and vitamin C. The retention of the organics under solar exposure has been shown to be significantly enhanced by the addition of TiO2:Mn to the formulation. In the case of BMDM and OMC, the retention is increased from 20% and 24% to 63% and 83%, respectively, after two hours of solar exposure. In this system, TiO2 particles are shown to provide only limited protection relative to BMDM and OMC. Vitamin E and vitamin C are actively degraded by the presence of TiO2 in the emulsion during solar exposure. This effect is reversed with TiO2:Mn, the use of which can protect 90% of anti-oxidants in both the oil and water phases of the formulation. The absence of reactive oxygen species (ROS) generation and surface scavenging of ROS by TiO2:Mn is responsible for a significantly reduced ROS load on the organic components and consequent photostabilization of the emulsion. INTRODUCTION Incident UV solar irradiation has been implicated in a number of skin pathologies. Conventionally, the UV portion of the solar spectrum is split into two regions, UVB (290-320 nm) and UVA (320-400 nm). UVA comprises 90-95% of incident UV radiation energy at the surface of the earth and penetrates deeper into the skin layer (20-50% can reach the melanocytes) than UVB (1,2). Although the skin penetration depth is much lower in the case of UVB radiation, UVB is approximately 1000 times more effective at causing sunburn and corresponding chromosomal damage as a result of direct UVB absorption, and as such UVB has historically been considered a more likely carcinogen than UVA. However, recent work has called this assumption into question Address all correspondence to J. Stott. 385