When properly distilled, essential oils should not contain traces of any heavy metals (i.e. mercury, arsenic, lead, etc.) because these types of molecules are too heavy and large to be volatilized under normal distillation conditions. However, if heavy metal contamination is suspected, Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) can be used to check a batch of oil and verify the absence of heavy metal contamination.
ICP-MS has gained acceptance as an effective method for conducting heavy metal analysis on essential oils because of its exceptionally sensitive detection capabilities. This testing method is used to determine the type and quantity of elemental constituents in an essential oil, especially heavy metals. ICP-MS testing uses a high-energy medium called inductively coupled plasma (ICP) to first ionize the sample. The sample is then run through a mass spectroscope machine which separates the sample into its elemental parts and provides a reading about which elements are present and at what quantities. On an ICP-MS reading, each element always shows up as a peak at its own characteristic location, therefore allowing identification of any heavy metals that may be present.