Development of High-Performance Thin-Layer Chromatography (HPTLC) Technique for Evaluation of Sunscreen Photostability

Sunscreens like 4-tert-butyl, 4-methoxydibenzoylmethane (BMDM) exhibit poor photostability, when exposed to sunlight. Conventionally, photostability of BMDM and other sunscreens can be determined using high-performance liquid chromatography (HPLC) or spectroscopic methods. We have developed a rapid, easy screening, and potentially high-throughput high-performance thin-layer chromatographic (HPTLC) method for quantifying the photostability of BMDM in the presence of known stabilizers/other chemical ingredients. The method is based on spotting the silica gel coated HPTLC plates (in duplicate) with the sunscreen molecules of interest along with a known photostabilizer. The plate is then exposed to solar simulated sunlight for a specific time. Ascending chromatography was performed in a thin-layer chromatographic (TLC) chamber using n-hexane-ethyl acetate 9:1 (v/v) as the mobile phase (∼10 mL). Densitometric analysis was done to determine the amount of sunscreen that remained after solar exposure. This method also involves separation of sunscreens and their photodegraded products on the HPTLC plate. The results obtained with this method were compared well with those obtained with the conventional method.