Analysis of Coumarin-Based Phototoxins in Citrus-Derived Essential Oils Using Liquid Chromatography-Mass Spectrometry

The occurrence of coumarin-based photoactive compounds in essential oils has been a concern due to the adverse health effects it has on human health. A fit-for-purpose analytical method for major coumarin-based phototoxins is critical to guarantee the essential oils product safety and compliance with the regulatory requirements. Herein, a liquid chromatography-mass spectrometry (LC–MS) analytical method was developed to identify and quantify 25 coumarin derivatives in essential oils. The sample preparation procedure was optimized to use selective solvent extraction to remove the limonene matrix interference. To achieve the optimal sensitivity and specificity, UHPLC column of biphenyl stationary phase was used for this analysis. An inter-laboratory validation study was conducted to evaluate the method performance. The limit of quantification (LOQ) for all target analytes was validated at 5 µg/g. Satisfactory recoveries were obtained for the majority of analytes in the range of 80–115%. Both the repeatability RSD_r (within-laboratory) and reproducibility RSD_R (between-laboratory) were < 10%. This method was demonstrated as applicable for the quality control testing of coumarin-based phototoxins in essential oils.