Turmeric oil, like many oils, is often subject to adulteration. One of the main kinds of adulteration is component-based adulteration. By adding in heavier, less expensive components, the adulteration might not be visible on a GCMS, depending on the length of time of the run or the length of the column used. Additions of 1,8-cineole from eucalyptus can also be used to dilute a turmeric oil.
Turmeric may also be adulterated by adding carrier oil or turmeric extract. Both are cheap ways to “dilute” the oil in a way that won’t necessarily be detected for the same reason as component-based adulteration. Also, an extract will have almost the same components. Cheaper oils can also be added, such as turmeric leaf, gurjun balsam, or low quality ginger.
When oils are adulterated, they can lose the constituent benefits of a pure oil. It is important to only buy oils from sources with a third-party tester that make their results public.