Alexis St-Gelais, M. Sc, Chimiste - Popularization
Essential oils are worth quite a lot of money. It so happens that, in order to boost profits, unscrupulous people alter oils in various ways. This "Adulterants and you" series is there to introduce you to some of the adulterations we encounter. This is because not all of them are necessarily obvious, nor bear the same level of risk for the final consumer.
I will be lauching this series with one of the diluents I have encountered the most in essential oils analyses: my now old "friend" ethylhexyl palmitate (figure 1).
|Figure 1. Structure of ethylhexyl palmitate.|
What is it?
It is obtained from the reaction of palmitic acid, a very common fatty acid, with 2-ethylhexanol, which is manufactured in huge quantities worldwide. As a pure compound, ethylhexyl palmitate is a slightly viscous, colorless and almost odorless liquid with a soft silicon-like texture. It is mostly used in the cosmetics industry: you can find a list of products sold in the USA that contain this ingredient on the Household Products Database of the United States Department of Health & Human Services. As any "good" diluent, it also is available at low-cost, for example here for 21,80$USD/kg as of August 2015.
What does it do as an adulterant?
Typically, this compound is used as a major diluent of essential oils. I most often observed it to represent more than 80% of the total volatile compounds detected in fraudulent oils, along with <1% ethylhexyl myristate, a closely related molecule. From a fraudulent point of view, it has the advantage of leaving the oil's aroma unaltered, making it very hard to detect the trick by smell only. As for the viscosity, the change is very subtle, and can easily be missed, especially for already somewhat viscous oils. There are also some cases where the fraudster seems to be somewhat aware that he can be caught, and uses less diluent, in the 5-10% range.
Is it dangerous?
No. Unlike some other adulterants, ethylhexyl palmitate has a very safe health profile, hence its presence in numerous cosmetics. A quick look on Reptox, the worker's health and safety database from the governement of Quebec, shows that ethylhexyl palmitate has no reported averse effect on health whatsoever unless absorbed in tremendous quantities. So, if you happen to get an oil cut with ethylhexyl palmitate, the most frustrating part will not be a health problem, but "only" losing your money over a product that contains only 10-20% genuine essential oil for the price of a pure sample. As always, this applies for regular uses. Essential oils, whether pure or adulterated, should not be taken orally, not put near the eyes or other sensitive parts of the body without proper dilution.
How do we detect it?
Happily for us, the compound can fairly well be detected in gas chromatography. The only requirement is for the analytical lab to run long enough methods to actually get the compound to show up, since it has a pretty high boiling point and is thus a late-eluter. It is very clearly separated from normal constituents of essential oils. Ethylhexyl palmitate singlehandedly justifies that we run our GC methods for almost 20 minutes more after the usual compounds we observe in essential oils, which translates on most of our reports in a long, blank baseline at the end of the chromatograms.
Bottom of the line
Ethylhexyl palmitate is a common, cheap diluent, fairly easy to detect for any skilled and knowledgeable laboratory, with no serious health concerns.