Carrier oils, or non-volatile oils, are often added at larger volumes to basil oil. This dilution of the pure oil can create larger quantities to be sold. DPG (dipropylene glycol), DEP (diethyl phthalate), or IOP (Isoctyl phthalate) are often used for this purpose.

In very tiny amounts, synthetic fragrances can also be used to adulterate essential oils. Laboratories who only run 30-60 minute tests on a GC-MS are unable to detect these adulterations. APRC specializes in detecting these smaller additions with longer tests and well-trained analytical chemists.