Measuring the Concentration or Content of Essential Oils

An essential oil is a concentrated hydrophobic liquid containing volatile chemical compounds derived from plants. Essential oils are also known as volatile oils, ethereal oils, or simply the oil of the plant from which they are extracted. An essential oil is considered “essential” in the sense that it contains the “essence” of the plant’s fragrance, for example lemon oil, lavender oil, rose oil, or hemp oil. Essential oils are distilled from leaves, stems, flowers, bark, roots, or other parts of plants. Contrary to the use of the word “oil,” essential oils do not have an oily appearance. Most essential oils are clear; some are yellow or amber in color. Since essential oils are complex mixtures of various chemical constituents, their composition can be influenced at every stage of production, starting with growing and harvesting conditions and ending with storage. Diluting, cutting, or extending high-purity oils with lower-quality products while still selling them as “pure” represents a critical issue that necessitates strict quality control. Especially when essential oils are used for health or therapeutic purposes, it is imperative that they are pure and of high quality.

There are several techniques for analyzing the composition and purity of essential oils. A common ISO quality standard for essential oils is the measurement of physical parameters. In addition to visual inspection of the oil and evaluation of its odor, the specific optical rotation, refractive index, and density are measured. These measurements can confirm or reject the authenticity of an oil’s declared botanical species and country of origin, while also potentially revealing any adulteration with foreign substances or dilution processes.

Vari Family for essential oil quality control

By using our new VariPol polarimeter, featuring full compliance with 21 CFR Part 11 and high reproducibility, reliable quality control of essential oils can be ensured. By adding the VariRef refractometer, a second parameter—the refractive index—can be determined in parallel. Furthermore, the VariDens can be used to determine the density of the essential oil, allowing all of the ISO standards mentioned above to be fulfilled.

Advantages of using the Vari Family:

• Time- and space-saving
• Non-destructive and easy to perform
• Rapid temperature control
• All devices can be controlled via display or remotely (PC, smartphone, tablet)
• Centralized data collection and evaluation

Normative references:

• ISO 592:1998-11 Essential oils – Determination of optical rotation
• ISO 280:1998-11 Essential oils – Determination of refractive index
• ISO 279:1998-12 Essential oils – Determination of relative density at 20 °C – Reference method