The quality control of essential oils (EO) principally aims at revealing the presence of adulterations and at quantifying compounds that are limited by law by evaluating EO chemical compositions, usually in terms of the normalised relative abundance of selected markers, for comparison to reference values reported in pharmacopoeias and/or international norms. Common adulterations of EO consist of the addition of cheaper EO or synthetic materials. This adulteration can be detected by calculating the percent normalised areas of selected markers or the enantiomeric composition of chiral components. The dilution of the EO with vegetable oils is another type of adulteration. This adulteration is quite devious, as it modifies neither the qualitative composition of the resulting EO nor the marker’s normalised percentage abundance, which is no longer diagnostic, and an absolute quantitative analysis is required. This study aims at verifying the application of the two above approaches (i.e., normalised relative abundance and absolute quantitation) to detect EO adulterations, with examples involving selected commercial EO (lavender, bergamot and tea tree) adulterated with synthetic components, EO of different origin and lower economical values and heavy vegetable oils. The results show that absolute quantitation is necessary to highlight adulteration with heavy vegetable oils, providing that a reference quantitative profile is available.

中文翻译：

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精油掺假：质量控制的多任务问题。三个案例研究： Lavandula angustifolia Mill.、Citrus limon (L.) Osbeck 和 Melaleuca alternifolia (Maiden & Betche) Cheel

精油 (EO) 的质量控制主要旨在揭示掺假的存在，并通过评估 EO 化学成分（通常根据所选标记的标准化相对丰度）来量化受法律限制的化合物，以便与报告的参考值进行比较在药典和/或国际规范中。EO 的常见掺假包括添加更便宜的 EO 或合成材料。这种掺假可以通过计算选定标记的归一化面积百分比或手性成分的对映体组成来检测。用植物油稀释 EO 是另一种掺假。这种掺假是相当狡猾的，因为它既不会改变所得 EO 的定性组成，也不会改变标记的标准化百分比丰度，这不再是诊断性的，需要进行绝对定量分析。本研究旨在验证上述两种方法（即归一化相对丰度和绝对定量）在检测 EO 掺假中的应用，示例涉及掺有合成成分、不同来源的 EO 的选定商业 EO（薰衣草、佛手柑和茶树）以及较低的经济价值和重质植物油。结果表明，绝对定量对于突出重质植物油掺假是必要的，前提是提供参考定量曲线。示例涉及掺有合成成分、不同来源和较低经济价值的 EO 以及重质植物油的选定商业 EO（薰衣草、佛手柑和茶树）。结果表明，绝对定量对于突出重质植物油掺假是必要的，前提是提供参考定量曲线。示例涉及掺有合成成分、不同来源和较低经济价值的 EO 以及重质植物油的选定商业 EO（薰衣草、佛手柑和茶树）。结果表明，绝对定量对于突出重质植物油掺假是必要的，前提是提供参考定量曲线。