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Comparative evaluation of different substrates for the in vitro determination of sunscreen photostability: spectrophotometric and HPLC analyses
Author(s) -
Scalia S.,
Mezzena M.,
Bianchi A.
Publication year - 2010
Publication title -
international journal of cosmetic science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 62
eISSN - 1468-2494
pISSN - 0142-5463
DOI - 10.1111/j.1468-2494.2009.00536.x
Subject(s) - high performance liquid chromatography , uv filter , chromatography , photodegradation , sun protection factor , spectrophotometry , chemistry , ultraviolet visible spectroscopy , degradation (telecommunications) , materials science , organic chemistry , medicine , dermatology , optics , telecommunications , physics , photocatalysis , computer science , catalysis
Synopsis Polymethylmethacrylate (PMMA) plates and Transpore TM tapes were compared as substrates for the in vitro evaluation of photostability of commercial sunscreen products. The sun care preparations were applied respectively on Transpore TM tapes and PMMA plates and their sun protection factors (SPF) and UVA protection parameters [UVA/UVB ratio, critical wavelength, UVA protection factor (UVA‐PF)] were measured by transmission spectroscopy, before and after irradiation with simulated sunlight. No significant differences were observed in the UV protection parameters measured on Transpore TM tapes or PMMA plates, before exposure to the solar simulator. Conversely, after irradiation, the SPF values of the sun care products exhibited marked variations between the two substrates, the decrease in SPF being greater on PMMA plates (31.3–63.1%) than on Transpore TM tapes (10.4–23.8%). Differences between the two substrates were detected also for the UVA protection parameters, although they were significant only for the UVA‐PF. The tested samples were assayed also by high‐performance liquid chromatography (HPLC) to assess the extent of photodegradation of the UV filters present in the examined formulations. The results showed that for the PMMA plates, the light‐induced decrease in SPF, as determined by spectrophotometry, fitted well with the percentage loss of ethyl hexyl methoxycinnamate (the only photounstable UVB filter present) measured by HPLC. Moreover, for the PMMA substrate, the UVA‐PF percentage reduction was consistent with the percentage degradation of butyl methoxydibenzoylmethane (the only photounstable UVA filter present) determined by HPLC. On the other hand, poor correlation between spectrophotometric and HPLC analyses was observed on Transpore TM tapes. Therefore, PMMA plates are more reliable than Transpore TM tapes as substrates for in vitro photodegradation tests of sunscreen products by transmission spectroscopy.