Determination of phototoxic furanocoumarins in natural cosmetics using SPE with LC-MS

Furanocoumarins are a class of naturally occurring phototoxic substances widely spread throughout the Umbelliferae and Rutacea families of plants. Plant extract of these families (e.g. citrus extracts) are commonly used as ingredients in fragrances and cosmetic products. Due to their phototoxicity these substances are regulated within the European Union according to the European Regulation (EC) No. 1223/2009 on cosmetic products. The proposed analytical workflow aims to swiftly screen out and determine the amount of phototoxic furanocoumarins in natural cosmetics employing solid-phase extraction (SPE). Cosmetic samples were first extracted in methanol and subsequently diluted in 35% (v/v) methanol before being applied to solid-phase extraction. The extraction procedure allows extraction of the eight target compounds including the six marker-substances proposed by the International Fragrance Association (IFRA) from complex cosmetic samples with satisfactory recovery levels ranging from 84 to 116% with the exception of bergamottin (68-89%). HPLC-UV and ESI-MS were used for the analysis of the target compounds. Furanocoumarin quantification was performed by standard addition. The workflow was successfully validated according to the ISO 12787 international standard ("Cosmetics - Analytical methods- Validation criteria for analytical results using chromatographic techniques"). Results of the validation on standard solutions highlight a LOQ of 0.01 mg kg^-1, acceptable linearity up to 1 mg/kg as well as good accuracy (Bias <15%) and precision (RSD <15%). Total furanocoumarin levels of the examined natural cosmetic products were in general in agreement with the European Regulation. However, it was shown that total levels of furanocoumarins might be significantly higher than assumed using the six proposed marker substances only.