An HPLC method for hydroperoxides derived from limonene and linalool in citrus oils, using post-column luminol-mediated chemiluminescence detection

Limonene and linalool are unsaturated terpenes commonly found as major components in many essential oils, and both are easily oxidized by atmospheric oxygen to form hydroperoxides. The hydroperoxides of both limonene and linalool are known to be sensitizers capable of causing allergic contact dermatitis, but with different potency. In addition, positional isomers of limonene hydroperoxide have been demonstrated to have different allergenic potencies. This creates a need for an analytical method that is capable of differentiating hydroperoxides derived from different terpenes, including the various positional isomers. The standard iodometric titration methods [peroxide value (POV) methods] typically used to measure hydroperoxide levels in essential oils provide only a total level of all oxidizing species, including hydroperoxides. These POV methods are not capable of species differentiation and therefore may not reliably correlate well with the skin sensitizing potency of a particular sample. A high-performance liquid chromatographic (HPLC) method using a post-column reaction to produce chemiluminescence via luminol oxidation was developed to address the need for a species-differentiating method. Copyright (c) 2015 John Wiley & Sons, Ltd.