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Written By Dr. Kevin Brigden
and Scott Ballard
A number of different components can have the same retention time. Similarly, the mass spectra of many components of essential oils are very similar. Using the multiple comparison approach outlined above helps to avoid misidentification that can occur when only one type of library is used. There are numerous examples of erroneous information within published oil composition data where only one type of library was used.
Percent composition
The percent composition figures quoted for each component of an oil are obtained from the mass spectrum detector. There are a number of different types of detector that are commonly used, and they all have slightly difference response factors to a particular component. The percentage figures quoted for each component may vary slightly from those obtained using, for example, a flame-ionisation detector (FID).
Mass spectrum detectors are far more accurate than an FID for component identification, which is why Kobashi use this type of detector for our primary analysis. We are currently analysing all our oils using a FID detector, in addition to the GCMS data we already have. In this way, we will be able to compare the composition of our oils with reported data from either type of detector to a very high degree of accuracy.
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Mass Spectrum
HP MS 5972 quadrapole detector,
GC 5890 and Auto Sampler
The main analysis on each oil is carried out using gas-chromatography / mass-spectroscopy (GC-MS). This type of analysis gives information about the individual components of each oil, and their relative amounts. See below for more information.
The physical properties of each oil are also tested to ensure that they are within the expected range for each oil (e.g., density).
GC-MS Analysis
Component identification
The different components of each oil are identified using the following databases;
1.) Comparison of the GC retention time with a retention time library.
a) Comparison of the mass spectrum with the Wiley 275’ mass spectra library, containing over 275 000 entries.
b) Comparison with pure ‘standards’ for certain- components, especially unwanted contaminants such as phthalates.
2.) Cross-referencing with other oils.
3.) Comparison with published data on each essential oil.
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