oil may not have exactly the same aroma each time you buy it.
Gas-Liquid Chromatography
It is possible to ‘read’ the formula of an essential oil using various techniques, the most common being the gas-liquid chromatograph (GLC). In this apparatus a minute amount of essential oil is injected into a temperature controlled, extremely fine, coiled, tubular column. The time taken (called the retention time) for each component to emerge from the other end of the column is different, depending on the molecule size. The quantity released is recorded, showing a peak on the trace (proportional to the quantity). This is a comparative test, not an absolute one, the retention time of known constituents having already been determined, to aid in the analysis.
As every batch of oil will vary in its percentages of components, one reading of each oil is kept as a ‘standard’. This standard can then be directly compared to that of another essential oil from the same plant.
This technique shows any added adulterant having a retention time not evident on the standard. However it is possible to adulterate an oil low in a certain constituent, simply by taking that constituent from another, usually cheaper, essential oil, to ‘correct’ its reading. Sometimes a synthetic replica of a component is used, and occasionally, where a high concentration of one ingredient is desired, the oil will have a percentage of its terpenes removed, as in peppermint oil (see chapter 4). Aromatherapists should be wary of such an oil as this ‘concentrates’ the active components. Alternatively an ingredient may be augmented, as in the case of eucalyptol added to eucalyptus oil.
FIGURE 2.3: Gas-liquid chromatographs
Of all tests carried out on essential oils, the most common, apart from the GLC, are infra red, optical rotation, specific gravity, mass spectrometry (very expensive, but excellent) solubility in alcohols and ester content.
Organically Grown Oils
The term ‘organic’ has different meanings to different people. To the aromatherapist it probably conjures up a vision of aromatic and medicinal plants growing in unpolluted conditions. To the chemist, it simply means a substance which contains the carbon molecule, for example, sugar. The French term biologique or ‘biological’ is probably a safer term to use when referring to organic plant production.
Many of us would like to see a return to organic growing for everything – it is better for the soil, better for the environment and generally results in a superior product. However, organic growing methods entail heavy labour costs, sometimes yielding less attractive results – compared (sadly) with chemically assisted supermarket-type produce. The improvement in flavour of organic fruits and vegetables should make up for the – often – smaller size and sometimes less attractive appearance!
Often, produce claiming to be organic is not, and it is necessary for British produce to have a certificate, e.g. from the Soil Association, as proof, which can be asked for by any discerning or suspicious shopper.
The same principle applies to the growing and buying of organic essential oils, the certificates being awarded by the country in which the plants are grown, e.g. Natur et Progrès, Biofranc, etc. in France, Demeter in Germany, and so on.
It is obviously better for a plant to utilize the nitrogen, phosphorus and potassium (NPK) in the soil than to be fed with chemically produced NPK. The farmers in Egypt, where some of our oils come from, occasionally use potassium sulphate and ammonium sulphate from local natural deposits beside the lake. Pesticides are rarely, if ever, used, yet I must say that if a swarm of locusts set upon their fields, I for one would forgive them for using them – I would not expect them to sit back and watch their crops being eaten. After all, their livelihood is at stake!
I believe that to have organic plants for consumption, i.e. in the production of dried herbs and fresh fruits, is an admirable idea. Although we do stock certificated oils, we also have some which are not certificated but are from biologically grown plants; I am not keen to claim these as organic for the following reasons:
1 It is a very expensive process, involving inspectors examining the soil and testing the plants from time to time for fertilizers and pesticides. The certificate-awarding body claim money not only from the farmer, but also at each transaction through to the final one, so the price of the essential oil at the end is rather high. By the way, nitrogen, phosphorus and potassium do not come through in distillation.
2 It cannot be taken for granted that a field of biologically grown plants is always free from contamination. What about acid rain, air pollution, polluted ground water, aerial crop spraying, radioactivity e.g. Chernobyl, etc. – all beyond the control of the farmer?
Nevertheless, for those who (like several of our French farmer suppliers) believe in natural methods, the belief itself has to be the reason for wanting organic essential oils and if these beliefs are serious, it is a pity to have to escalate the price by buying proof, unless it is impossible to sell the crop (or the oils) without it. It may come to this one day, simply because some people will sell oils without certificates, claiming they are organic, when in fact they are not – just like the fruit and vegetable trade!
3 Aromachemistry – the Chemistry of Essential Oils
We are now going to take a look at the fundamentals of essential oils – the structure and effects of their chemical components. I want you to enjoy this chapter, and I hope you find it absorbing and stimulating.
Essential oils can be classified in several ways and if you know the chemical composition of an oil you can make a fairly good guess as to its therapeutic effects and possible hazards. There is no need for me to go into great detail – as my husband puts it, ‘It is quite safe to drive a car without being a qualified mechanic, so long as we understand the simple basic principles of how the car works and we have learnt to control it.’
I shall explain only the basics, very simply and I hope clearly, so that you can appreciate the significance of the components which make up the oils – and their relationship with one another. This way, you will get to know these precious gifts of nature and be able to use them in an understanding and respectful way.
Everything in the world, both living and non-living, is made up of chemicals. Most of the chemistry I learned at school was about things that are non-living and have never lived – this is called ‘inorganic’ chemistry. The chemistry which includes all living things (and those which have once lived) is called ‘organic’ chemistry or the chemistry of the carbon compound, since all organic substances contain carbon. The two main groups of chemicals in organic chemistry are referred to as chain or aliphatic and ring or aromatic (not necessarily meaning odorous).
Carbon, hydrogen, nitrogen and oxygen (this last accounts for nine-tenths of the human body!) are the basic building blocks of life itself, each of them being composed of atoms, the atom itself being thought at one time to be the smallest particle in existence.
Atoms
The building blocks of the universe! Every atom has a nucleus containing one or more protons, which are electrically positive, and one or more neutrons, which are neutral. Around the outside, depending on the particular atom, there are one or more
