A sensitive LC–ESI-MS/MS method for the quantification of avobenzone in rat plasma and skin layers: Application to a topical administration study

•A sensitive LC–MS/MS method was developed to quantify avobenzone in rat biological matrices.•The assay was validated for rat plasma, stratum corneum, epidermis, and dermis.•A percutaneous absorption of avobenzone was examined in rats after topical application.•Avobenzone was found to penetrate into the skin layers but was not absorbed in the circulation.

This study describes the development of a sensitive high-performance liquid chromatography–electrospray ionization-tandem mass spectrometry (LC–ESI-MS/MS) method for the quantification of avobenzone in rat plasma and skin layers. Separations were performed on a Zorbax SB C8 column using a binary gradient mobile phase composed of acetonitrile and 0.1% formic acid in water. The assay achieved LLOQ of 0.5 ng/ml for plasma, 5 ng/ml for stratum corneum, and 10 ng/ml for epidermis and dermis. This method was applied to a percutaneous absorption study of avobenzone in rats. At 12 h following topical application of emulsion and lotion (applied amount of avobenzone 11.7 mg/kg), avobenzone was found primarily in the stratum corneum (16.3–17.8%) followed by epidermis (2.0–3.4%) and dermis (0.11–0.15%). Avobenzone was not quantifiable in the plasma samples collected over a 12 h sampling period. Given the excellent plasma assay sensitivity, this study provides evidence that the systemic absorption of avobenzone is insignificant, if any, after topical application.