Because of the high demand for sandalwood essential oil, as well as the resulting rising costs and the sandalwood tree’s diminished population around the world, sandalwood oil is one of the most adulterated essential oils. Adulteration involves many different methods in the essential oil industry, including the addition of a single raw material, cheaper essential oils, cheap synthetics, isolates, and even attempts to pass one essential oil off as another. When adding a single raw material to essential oils, rapeseed oil is often used in the EU as a cheap vegetable oil (Burfield, http://www.users.globalnet.co.uk/~nodice/new/magazine/october/october.htm, 2003).
The most common materials used to dilute sandalwood essential oil are the essential oils of other species of sandalwood (resulting in a blended sandalwood essential oil), as well as copaiba (Copaifera) oil, Atlas cedar (Cedrus atlantica) fractions, and amyris (Amyris balsamifera) oil. Sandalwood fragrance chemicals, synthetic substances which are not originally from the sandalwood tree, are often added to other oils to recreate sandalwood oil’s natural fragrance. Adulteration of sandalwood oil can also often involve a technique called “stretching,” where odorless solvents are added to sandalwood oil to increase its quantity.
Besides the adulteration of sandalwood essential oil, many synthetic substitutes for sandalwood oil, which originate from chemicals rather from the actual sandalwood tree, exist today. Beta-santalol is the main olfactory constituent of sandalwood oil, and it wasn’t until 1990 that beta-santalol could be prepared in a laboratory. According to experts in the creation of synthetic essential oils, “The components in sandalwood oil are not easy to make. Synthetic oil manufacturers often search many other substances to find “woody notes” similar to sandalwood oil. Experts also note that “The best sandalwood oil substitutes are derivatives of alpha-campholenic aldehyde, prepared from inexpensive alpha-pinene, most of which is a byproduct of the paper industry.” The campholenic aldehyde derivatives often possess a scent similar to sandalwood. Other olfactory parts of natural sandalwood oil—including the smoky, cedar-like fragrance—can be imitated by using cedar wood oil (Royal Society of Chemistry, http://www.rsc.org/chemistryworld/Issues/2009/February/TheSweetScentOfSuccess.asp, 2009).
While synthetic sandalwood substances are often used to adulterate sandalwood essential oil in an attempt to cheat the sandalwood essential oil and perfumery industry, this is not always the case. The company Tru Fragrance, for example, claims that their synthetic blend smelling of sandalwood called ‘HipNote Sandalwood’ is for practical sustainability purposes: “The use of synthetic substitutes within the fragrance world, like those found in ‘HipNote Sandalwood’ and many of the season’s product launches, are essential in assisting in sustainability efforts, helping to ensure the fragrance development process does not destroy natural resources” (Perfume Shrine, http://perfumeshrine.blogspot.com/2011/05/perfumery-material-sandalwood-synthetic.html, 2011).
Because sandalwood is in such high demand and is so often adulterated, it has become increasingly important to those purchasing sandalwood essential oil that this oil is authentic and pure. This issue is especially important for the perfume, pharmaceutical, flavor, and fragrance industries. There are many different ways to test sandalwood oil’s authenticity. Sometimes adulteration of sandalwood oil is easy to detect; in other cases, adulteration is conducted by an expert with the right materials and requires advanced technology to analyze. Often, a trained expert on sandalwood oil can detect adulterated oil simply by the aroma. In other cases, more complex chemical, instrumental, and physiochemical tests are used. GC-MS (gas chromatography–mass spectrometry) analysis of sandalwood oil is a common method to identify the authenticity and purity of the oil; the data for the oil can be compared with standards, or “fingerprints,” for sandalwood oil to make determinations about its purity. Physiochemical tests help establish the identity of oil based on the fact that authentic essential oils have fixed characteristic values for specific gravity/relative density, refractive index, and optical rotation (Burfield, http://www.users.globalnet.co.uk/~nodice/new/magazine/october/october.htm, 2003). Most recently, in 2010 a scientific study in India introduced the potential use of Near Infrared (NIR) spectroscopy along with a few other techniques as methods to determine whether or not sandalwood oil has been adulterated (http://www.ncbi.nlm.nih.gov/pubmed/20820490, 2010).