A NEW IN VITRO METHOD TO DETERMINE SPF 105 Figure 2. In vitro SPF test for commercial sunscreen lotion (SPF 30, PA++) by EBT3 fi lm method. Figure 3. In vitro SPF test results of different UV irradiation time based on EBT3 fi lm. to 0. As other in vitro SPF test methods, the EBT3 fi lm method could also be improved by optimizing test parameters, such as sunscreen amount, irradiation time, and EBT3 fi lm, as long as the reproducibility is good. Similar to the in vivo SPF test, the EBT3 fi lm method considers the photostability of sunscreens. If the sunscreen is degraded under UV light, the SPF value measured should be lower than that measured by UV spectrophotometer. For example, samples 1 and 6 (SPF 15) might have low photostability which results in

JOURNAL OF COSMETIC SCIENCE 106 Table I SPF Test Results Based on EBT3 Film for Commercial Sunscreen Products (1–8 Products—Organic UV Filters Only 9–15 Products—Organic and Inorganic UV Filters) Commercial sample Labeled SPF (in vivo)a In vitro SPF results (EBT3 fi lm) UV fi lters 1 FDA:14.0, ISO:16.2 3.2 BP-3, EHDP 2 Colipa:16 16.6 EHMC, OCR, BMDM, BEMT 3 SPF 15, PA++ 14.6 EHMC 4 SPF 30, PA+++ 34.5 EHMC, MBBT, BEMT 5 SPF 20, PA++ 19.2 EHS, HMS, OCR, BMDM, Ensulizole, PBSA 6 SPF 15, PA++ 7.3 EHMC, BMDM, PBSA 7 SPF 25, PA++ 22.5 EHMC, OCR,EHT,DHHB,MBBT, BEMT 8 SPF 50 51.7 BMDM, HMS, EHS, OCR, EHMC 9 SPF 30, PA++ 29.8 ZnO, EHMC, OCR, DHHB 10 SPF 30+, PA+++ 18.1 TiO2, EHMC, OCR, PBSA 11 SPF 50+, PA++++ 49.9 ZnO, EHMC, DHHB, OCR 12 SPF 15, PA++ 3.0 EHMC, BMDM, TiO2, MBC 13 SPF 30, PA+++ 31.5 HMS, PBSA, OCR, MBC, TiO2, BMDM, Neo Heliopan AP 14 SPF 30+, PA++ 34.2 EHMC, OCR, DHHB, TiO2, MBBT, PBSA 15 SPF 50+, PA+++ 61.8 EHMC, OCR, ZnO, TiO2 16 SPF 30, PA++ 30.5 ZnO 17 SPF 30+ 19.7 ZnO, TiO2 ISO: International Organization for Standardization. a Where inexact SPF values were given, additional SPF 5 added on labeled value. For example, for SPF 30+, SPF 35 will be used in the calculations. lower SPF results as compared to labeled value. All products tested in this study were performed at least in triplicate. The results of each test proved similar (data not shown). Sunscreen products containing inorganic UV fi lters are diffi cult to measure accurately with in vitro SPF tests based on UV spectrophotometers. The results for commercial prod- ucts with both organic and inorganic UV fi lter (sample 9–15) and the correlation of EBT3 fi lm results and labeled SPF value is illustrated in Figure 5. The trend line of EBT3 fi lm data is R2 of 0.8552. All products tested in this study were performed at least in triplicate. The results of each test proved similar (data not shown). Figure 4. Correlation of in vitro EBT3 fi lm results and labeled SPF for products only with organic UV fi lters.