JOURNAL OF COSMETIC SCIENCE 594 30 sunscreen, with its absorbance spectrum being close to the dynamic range limits of the transmittance analyzer. These limitations prohibit the evaluation of high SPF sunscreens on a roughened quartz substrate. The utilization of the roughened quartz substrate also creates the following technical problems: CV values were much higher than the required 10% or less for all tested products due to the lack of uniformity. An alternative substrate, Vitro Skin® N-19, worked well with the application dose recommended by the FDA however, it was found that the application time of ten seconds was not suffi cient to evenly apply the sunscreen over a relatively large application area. Thirty seconds of application time seems more reasonable in conjunction with this substrate. It was possible to obtain CV values of 10% or less on the alternative substrate. The surface of Vitro Skin® N-19 is more effi cient in de-emulsifying sunscreen emulsions and supporting low spot-to-spot variability during the transmittance measurements compared to the roughened quartz plates proposed by the Figure 3. Absorbance spectra of experimental sunscreen P (SPF~30) with “highest” UVA rating (Labsphere UV 2000S Vitro Skin® N-19 Q-Glass). Figure 4. Absorbance spectra of test articles after irradiation (Labsphere UV 2000S Vitro Skin® N-19).

Table V Test Articles and Their Respective UVAI/UV Ratios Obtained with Labsphere UV 2000S and with Vitro Skin ® N-19 and Roughened Quartz (Q-glass) Substrates Commercial sunscreen products Experimental A C D E K L N P Boots Five Star 2156-16 2156-18 Actives SPF-15 SPF-15 SPF-15 SPF-30 SPF-30 SPF-25 SPF∼50 SPF∼30 Avobenzone 3 2 3 + + 3 3 Octocrylene 10 2.35 + + 2.3 2 Homosalate 10 8 + Octisalate 5 4 + + Oxybenzone 5 3 5 Octinoxate 7.5 + Bemotrizinol (USAN) + 2 2.3 Bisoctrizole (USAN) active 6 3.5 Diethylhexyl butamido triazone + Pre-irradiation dose, MED 10 10 10 20 20 17 33.3 20 Vitro Skin UVAI/UV ratio 0.905-0.926 0.469-0.519 0.750-0.787 0.853-0.862 0.880-0.893 0.734-0.736 0.960-0.964 0.950-0.954 Q-Glass UVAI/UV ratio 0.929 0.912 0.948-0.955 FDA UVA rating High Medium High High High High Highest Highest CHALLENGES TO SUNSCREEN EVALUATION 595