Copyright ©Tony Burfield 2003-2005.
[Slightly updated from a Presentation to
the IFA Annual AGM London Oct 11th 2003].
Part 1. Oil Adulteration.
As far as adulteration is concerned, producers and distributors of essential
oils are frequently painted as “the bad guys”, but it should
be pointed out that their oil customers frequently demand oils below the
market price while still wanting to be told that they are authentic. In
this climate, the honest oil trader may find it virtually impossible to
survive on the margins he is allowed to make (many have already gone bust).
For example, in the late 20th Century, lavender oil (Lavandula angustifolia)
was being sold almost as a loss leader by many French producers as the
market was unwilling to pay a realistic price; currently, the aroma industry
is dominated by a handful of large and powerful international houses whose
corporate buyers often attempt to drive raw material prices to impossibly
low levels, not allowing workable profits to be made. This sets the scene
for unethical practices.
Essential oils - a definition.
An essential oil (e.o.) is the volatile oil containing odiferous elements
of the plant, produced by steam or hydro-distillation of aromatic vegetable
plant matter. E.O. components arise via the secondary metabolism of plants
and are stored within specialised structures; ideally they are isolated
with minimum chemical changes from human intervention. Citrus oils, produced
by the mechanical pressing of citrus peels, are also called essential
oils, and, according to the International Standards Organisation (ISO),
so are dry-distilled oils - such as cade oil (from the branches of Juniperus
oxycedrus) and styrax pyrogenée (from Liquidamber spp).
Essential oils should be produced by purely physical means, and be 100%
pure and wholly derived from the named botanical source - but how are
these standards to be guaranteed? No quality standards for the authentication
of essential oils exist in aromatherapy, in spite of the revelations of
gross adulteration of aromatherapy oils for retail sale (Health Which
2000). Professional aromatherapy organisations have failed to issue standards,
in spite of individual schemes being put forward (Jones 1998) but, in
contrast, other essential oil-using industries are served by the following
The Pharmaceutical Trade: British Pharmacopoeia (BP) 2004 is published
on recommendation of the Medicines Commission UK. Oils specifications
are also published in the European Pharmacopoeia 4th edn 2002 (Eur. Pharm
4th edn); United States Pharmacopoeia (USP); also the pharmacopoeia’s
of individual nations such as China, India etc. Earlier editions of The
British Pharmaceutical Codex (BPC), such as BPC 1949, contain many essential
oil standards still in use today.
Essential Oil Trade: Monographs on individual essential oils (EOA Standards)
were produced by the Scientific Committee of the Essential Oil Association
Flavourings Industry: Food Chemicals Codex IV (1996, US) produced at the
request of the FDA (1992), is widely used for guidance by the food flavourings
Aroma Companies: Many larger established Flavour & Fragrance Houses
have their own internal purchasing standards.
Independent Certifying Bodies: International Standards Organisation (ISO
Standards TC 54) & Association Française de Normalisation (AFNOR)
both have detailed standards for e.o.’s.*
*An example is ISO 3515 for Oil of Lavender (2001) which includes minimum
and maximum percentages of thirteen natural components, and their occurrence
in French (spontaneous and clonal), Bulgarian, Russian, Australian and
‘other origin’, lavender oils. Limits for lavandulyl acetate,
for example, are set at 2.0-5.0% in Bulgarian lavender oil by the standard.
Whilst it is apparent that the current European Pharmacopoeia, USP or
ISO standards may serve the needs of particular industrial sectors, they
do not entirely address the unique needs of the aromatherapy profession,
Holistic aromatherapists demand that “pure” and “complete”
oils are used, rather than oils only distilled for economically short
periods e.g. tea tree oil. It is now suggested that in some cases longer
distillations may be disadvantageous e.g. for tea tree oil distillation
again, increases, the proportion of sesquiterpenes rises and these are
considered by some researchers as responsible for adverse skin reactions
when applied topically. Secondly unnecessary energy ‘wastage’
associated with excessively long distillation times may not be seen currently
as a particularly “deep green” strategy!
Many essential oils used in aromatherapy are particular to that industry,
and not necessarily extensively used elsewhere e.g. Ravensara aromatica,
Rosemary oil verbenone chemotype, Helichrysum italicum ssp. serotinum
As well as “pure and natural”, the words “wild-crafted”,
“organic” and “clinical grade” are frequently
over-hyped descriptor terms used by both aromatherapy and by “naturals”
traders, which need more careful definition prior to professional endorsement.
Natural perfumers are other potential users of pure essential oils. Grimshaw
(1989) discussed “purist” perfumers (who employ no chemically
produced or chemically modified ingredients), but also discussed reasons
why others may wish to use up to 50% synthetics in formulations. This
was, in a way, a prediction today’s situation, whereby aromachology
perfumes (worth £611 million for years 1999-2001 according to Mintel
Database 2002) contain a proportion of synthetics stipulated by the perfume
house, mixed in with the e.o.’s. The alleged psychopharmaceutical
effects of these products still depend on the utilization of authentic
essential oils in the formulation – as far as marketing claims/hype
are concerned anyway. A realistic “in-practice” distinction
between mass-marketed aromatherapy perfumes (as opposed to 100% e.o. blends)
and aromachology perfumes, other than at a hypothetical level, has yet
to be defined, since both commonly employ synthetics. The synthetics content
can presumably have either symbiotic, neutral or opposing effects (mood
changing etc.) to those claimed for the e.o.’s in the perfumes in
question, hence the need for clinical testing of the finished formulations
to support advertising claims.
Types of adulteration.
There are several distinct categories of adulteration:
1. Addition of single raw materials. This simple form of adulteration
can be conveniently divided into two groups:
“Invisibles” – i.e. those materials undetectable by
a gas chromatograph (GC) analysis operating under routine conditions to
“Visibles – those materials normally detectable by GC.
“Invisibles”: an example of this type is the deliberate addition
of vegetable or mineral oil to essential oils (Nour-el-Din et al. 1977)
- rapeseed oil in the EU is a particularly cheap vegetable oil which has
been used for this purpose. Theoretically the “total area”
of the detectable components of the oil’s gas chromatogram should
be reduced by this latter type of adulteration, creating suspicion for
the analyst and the need for further investigation. These adulterant materials
may be revealed by aqueous alcohol solubility tests, and their presence
further verified by using a different GC column & operating conditions
(to detect mineral oil), or by derivatisation (for example the use of
a methylating agent for vegetable oils – whereby the volatile methyl
esters of the fatty acid components of glyceryl esters are revealed by
subsequent GC analysis).
“Visible” diluents in this context include a number of solvents
and perfumery materials. For example the following have been found in
commercial essential oils: in a few instances resulting in a warning or
prosecution by regulatory authorities:
Abitol (a primary hydroabietyl alcohol) – often used for extending
Benzyl alcohol (now classified as a sensitiser by SCCNFP opinion)
Benzyl benzoate (now classified as a sensitiser by SCCNFP opinion; formerly
widely used to extend resinoids)
Carbitol (diethylene glycol monoethyl ether or DEGME)
Dipropylene glycol (DPG)
Dipropylene glycol methyl ether (DPGME) and tripropylene glycol methyl
(TPGME) - both of these substances are in air freshener technology.
Herculyn DÔ (hydrogenated methyl ester of rosin)
Isoparä (odourless kerosene fractions often used as a candle perfume
Isopropyl myristate (IPM)
Phthalate esters such as di-n-butylphthalate (DNP), diethyl phthalate
(DEP) and di-
iso-octyl phthalate (DIOP)
Triacetin (the anti-fungal compound glycerol triacetate - a popular food
Use of materials like isotridecyl acetate (ITDA, Fixateur 404Ô),
Herculyn D and Abitol, can be moderately difficult to spot, because the
materials may show a myriad of late-eluting small peaks on a GC trace
representing their different constituent isomers, which could be overlooked
by an inexperienced analyst especially at low levels.
In all the above instances of “visible” and “non-visible”
adulterants, the added material is merely a diluent, and makes no odour
contribution of its own. Addition of 10-14% of such a material may pass
un-noticed if the material is evaluated against a retained standard solely
on an odour basis – even by an expert nose – but it will in
all probability be revealed by subsequent physio-chemical testing e.g.
added vegetable oil in patchouli oil can often be revealed by a solubility
test in 90% alcohol at 20°C.
2. The addition of cheaper essential oils and adjuncts.
Blending in cheaper oils to meet a customers’ target purchasing
price, or to make additional profit for the producer, is commonplace in
the oil trade. Some practices mentioned by Arctander (1960) - for example,
the practice of extending of Amyris oil (Amyris balsamifera) with Cedarwood
oil Virginia (Juniperus virginiana) and Copaiba Balsam (Copaifera spp.)
– are unlikely to fool too many potential customers in these present
& more educated times, but other more common adulteration practices
still remain, which include:
Bergamot oil (Citrus bergamia): addition of lemon oil, rectified ho oil
spp.) and acetylated ho oil.
Bitter orange oil (Citrus aurantium subsp. aurantium): addition of sweet
oil (Citrus sinensis) & orange terpenes, plus trace amounts of character
Cedarwood oil Virginia (Juniperus virginiana): addition of cedarwood oil
Chinese (Cupressus funebris).
Cinnamon bark oil (Cinnamomum zeylanicum): addition of cinnamon leaf oil.
Cinnamon leaf oil (Cinnamomum zeylanicum): addition of clove fractions,
eugenol, cinnamic aldehyde etc.
Clove Bud oil (Syzygium aromaticum): addition of clove stem oil &
(eugenol) & eugenyl acetate.
Fir Needle oils (Abies spp.): addition of turpentine fractions, camphene,
bornyl acetate etc.
Geranium oil Chinese (Pelargonium hybrids): addition of adulterated Indian
geranium oil (which itself has been known to contain diphenyl oxide!)
Grapefruit oil (Citrus paradisi): addition of orange terpenes or sweet
distilled + minor amounts of (+)-nootkatone & others.
Lavender oil (Lavandula angustifolia): addition of cheaper lavandin (Lavandula
x intermedia) oil varieties; the addition of spike lavender oil (Lavandula
latifolia); the addition of ho oil rectified (Cinnamomum spp) and acetylated
ho or acetylated lavandin oils etc.
Lemon oil (Citrus limon): addition of orange terpenes, lemon terpenes
products (e.g. steam-stripped lemon oil). For lemon oil BP, expressed
grapefruit oil is added to poor grades to raise the UV absorbance level
sufficiently to pass the BP specifications.
Nutmeg oil (Myristica fragrans): the addition of nutmeg terpenes, a- pinene,
limonene, turpentine fractions etc.
Patchouli oil (Pogostemon cablin): addition of gurjun balsam (Dipterocarpus
spp.); vegetable oils, Hercolyn D; patchouli and vetiver distillation
The superior Indonesian patchouli oil is often blended with the cheaper
Petitgrain oils (Citrus spp): addition of other citrus leaf oils &
aldehydes, linalyl acetate, orange terpenes etc.
Peppermint oil (Mentha X piperita): addition of cornmint oil (Mentha arvensis).
Sandalwood oil EI (Santalum album): addition of sandalwood terpenes,
sandalwood fragrance chemicals etc.
Rosemary oil (Rosmarinus officinalis) addition of eucalyptus oil Eucalyptus
globulus) & camphor oil white (Cinnamomum camphora).
Verbena oil (Lippia citriodora): L. citriodora herb distilled over lemon
Violet Leaf absolute (Viola odorata): addition of spinach absolute (Spinacia
Ylang Ylang oil qualities (Cananga odorata subsp. genuina): addition of
cananga oil (Cananga odorata), ylang ylang oil tails etc., ylang ylang
And also addition of these synthetics to “convert” one oil
Basil oil exotic: add linalol to convert to Basil oil Sweet (Arctander
Eucalyptus globulus: add a-terpineol & others to convert to Eucalyptus
Geranium oil Chinese to Geranium oil Bourbon: addition of balancing
materials (monoterpene alcohols and esters, especially formates), copper
chlorophyll (for colour) and frequently a trace of dimethyl and/or dibutyl
Tangerine oil (Citrus reticula var. tangerine): addition of g-terpinene,
anthranilate, a-sinesal & perilla aldehyde to convert to Mandarin
reticulata var. mandarin).
3. The addition of cheap (nature identical) synthetics to oils that naturally
contain these materials. Little detailed guidance has been previously
published in this area. The older work of Arctander (1960) mentions a
number of adulteration practices, but the sophistication of customer quality
control procedures probably means that of the noted practices are now
too obvious for today’s market. Looking at other published material
on adulteration, Singhal et al. (2001) remarks on the adulteration of
spice oils by simple additions of single raw materials e.g. the addition
of synthetic citral to Litsea cubeba oil. My own guide to questionable
practices include the following:
Anise oil (Pimpinella spp.): addition of technical grade anethol.
Basil oil exotic (Ocimum spp.): addition of methyl chavicol & linalol.
Benzoin resinoid (Styrax spp.): addition of small amounts of vanillin,
benzoate, ethyl & benzyl cinnamates, benzoic acid etc. to enhance
to pass off cheaper “Sumatra” grades as “Siam”).
Bergamot oil (Citrus bergamia): addition of linalol and linalyl acetate.
Bitter almond oil (Prunus amygdalus var. dulcis ): addition of, or passing
benzaldehyde, as the oil.
Buchu leaf oil (Barosma betulina & B. crenulata): addition to cutters
monoterpene sulphide fractions synthesised from the hydrogen sulphide
treatment of pulegone, including p-menthan-8- thiol-3-one.
Cassia oil (Cinnamomum aromaticum): the addition of synthetic cinnamic
aldehyde, methyl cinnamic aldehyde & coumarin.
Chamomile oil Roman (Anthemis nobilis): addition of isobutyl angelate
Cinnamon bark oil (Cinnamomum zeylanicum): the addition of synthetic
benzaldehde, eugenol and cinnamic aldehyde.
Citrus oils: the addition of fatty aldehydes and monoterpene alcohols
esters to terpeneless and folded citrus oils.
Caraway seed oil (Carum carvii): the addition of limonene and (+)-carvone
Cardamom oil (Elletaria cardamomum): addition of linalyl acetate, 1,8-cineole
Celery seed oil (Petroselenium crispum): the addition of limonene + touches
Cognac oil: addition of ethyl esters of aliphatic acids e.g. ethyl oenanthate.
Coriander seed oil (Coriandrum sativum): addition of linalol and trace
of certain pyrazines. NB price fluctuates – not always economic!
Cypress oil (Cupressus sempervirens): addition of a-pinene, d-3-carene
Cumin seed oil (Cuminum cyminum): addition of cuminaldehyde and others.
Dill seed oil (Anethum graveolens): addition of a-phellandrene & limonene.
Elemi oil (Canarium luzonicum): addition of a-phellandrene & limonene.
Galbanum resinoid (Ferula galbaniflua): addition of b-pinene, undecatrienes
Garlic oil (Allium sativa): addition of aliphatic sulphide mixtures containing
2-propenyl disulphide, 1-propenyl disulphide etc.
Jasmine absolute (Jasmimum spp): reconstructions frequently added.
Juniper oil (Juniperus communis var. erecta): addition of terpene
hydrocarbon mixtures containing a-pinene & d-3-carene, also Juniper
oil and second grade oils from spoiled Juniper berries.
Labdanum resinoid (Cistus landiferus): formerly, the addition of DEP (now
discontinued) or Abitol, with small amounts of ambroxan and p-methyl
acetophenone to enhance odour.
Lavender oil, spike (Lavandula latifolia): addition of eucalyptus &
camphor oil fractions, spanish sage oil etc.
Lemongrass oil (Cympogon spp.): addition of citral.
Mentha citrata oil: addition of linalol + linalyl acetate.
Mustard oil (Brassica nigra & B. juncea): allyl isothiocyanate passed
off as the
oil (which is used in flavourings, but is banned in perfumery &
Neroli oil (Citrus aurantium subsp. aurantium): reconstructions frequently
added to, or passed off as the authentic oil.
Origanum oil (Origanum spp.): addition of para-cymene and carvacrol.
Onion oil (Allium cepa): addition of aliphatic sulphide mixtures.
Palmarosa oil (Cymbopogon martinii var. motia): the addition of geraniol.
Petitgrain oil Paraguay (Citrus aurantia subsp. aurantium ): addition
admixture of linalol, linalyl acetate, a-terpineol, geranyl & neryl
trace amounts of pyrazines etc.
Pine needle oils (Pinus spp.): addition of (-)-bornyl acetate, isobornyl
limonene, a-pinene, camphene etc.
Rose oil: reconstructions using damascones, b-ionone plus (-)-citronellol
and other rose alcohols, plus rose steroptenes. Occasionally adulterated
phenylethyl alcohol, rhodinol fractions and cheaper rose oils (Morocco,
Rosemary oil (Rosmarinus officialis): addition of camphor, isobornyl acetate
Eucalyptus & turpentine oil fractions).
Rosewood oil (Aniba spp): addition of linalol, plus trace amounts of methyl
heptenone, methyl heptenol, 3-octanol, para-methyl acetophenone etc.
Spearmint oil (Mentha spicata): addition of (-)-carvone.
Thyme oil (Thymus spp.): addition of para-cymene & thymol. “Red
thyme oil” is
often wholly synthetic.
Vetiver oil acetylated (Vetivera spp): the addition of cedrenyl acetate.
Wintergreen oil (Gaultheria procumbens): the adding of, or passing off
salicylate, as the oil.
Ylang ylang oil (Cananga odorata var. genuina): addition of benzyl acetate,
methyl benzoate, para-cresyl methyl ether, geranyl acetate, benzyl benzoate,
benzyl cinnamate, cedarwood oil and others or complete
Boelens (1997) described four types of odourants in essential oils: character
compounds, essential compounds, balance compounds and artifacts. Adulterants
such as monoterpene hydrocarbons, being balance compounds in Boelens scheme
above, do little for the characteristic odour of the cut oils, since the
added materials have little odour value in themselves. In practice, the
addition of certain adulterants “flattens” the odour profile
of the authentic oil, or otherwise dilutes or represses some true character,
sparkle and richness. To compensate for this, a practiced oil counterfeiter
will add small amounts of character compounds. Taking the example of Cypress
oil Cupressus sempervirens var. stricta, the oil is often adulterated
by the addition of the monoterpene hydrocarbons a-pinene and d-3-carene,
which creates a crude terpinic aspect. The addition of a small amount
of deca-2-(E),4-(Z)-dienyl isovalerate to the somewhat insipid cutting
agent, will give a better impression of the oil’s normal character,
a lead which follows on from the work of Garnero et al. (1978) who identified
the compound above in cypress shoots, and found it strongly reminiscent
of the typical odour of cypress oil.
Commercial oils, adulterated by such synthetics, can often fool the less
sophisticated nose, or satisfy those oil customers buying to a price,
where authenticity is sometimes not a primary consideration. Depending
on exact market conditions, some oils have a selling price which is so
cheap that it is generally unrewarding for a trader to reconstitute, or
even add, nature identicals to the product, except for some solvent-like
diluents. This category includes the following oils:
Sweet orange oil (Citrus sinensis)
Clove leaf oil & stem oils (Syzygium aromaticum)
Citronella oil (Cymbopogon spp.): (but the oil has been known to have
crudely adulterated with dipentine and citronella terpenes)
Camphor oil white (Cinnamomum camphora fractions)
Cornmint oil (Mentha arvensis subspp).
Eucalyptus globulus oil
Tea tree oil (Melaleuca altenaria) (NB a collapse in market price means
adulterants such as terpinen-4-ol and a- & g-terpinenes can now be
as the oil).
Other oils are difficult to reconstitute with anything other than diluents
because the major components are not commercially available; this class
of oils includes patchouli oil, vetiver oil and to some extent ginger
4. The addition of isolates or natural components to essential oils e.g.
the addition of pure natural eucalyptol ex E. globulus oil (Eucalyptus
globulus) to rosemary oil (Rosemarimus officinalis) or rectified ho oil
(very high in
(-)-linalol) to lavender and bergamot.
5. The addition of bases or reconstituted essential oils to genuine oils
& absolutes. It is particularly economically attractive to extend
high value floral absolutes such as rose (Rosa spp.), jasmin (Jasminum
grandiflora other spp.) and osmanthus (Osmanthus fragrans var. auranticus),
and the more valuable oils such as neroli oil and rose otto, and this
practice occurs extensively within the trade.
6. The addition of individual unnatural components to oils and aromatic
Absolutes have been traditionally produced for the consumption of the
perfumery industry, but are being increasingly employed in aromatherapy
(in spite of using un-natural solvents in their manufacture). Revelations
that materials such as Linden Blossom absolute (Tilia spp.) contain hydroxycitronellal,
or that Gardenia absolute (Gardenia spp.) has added styrallyl acetate,
or that added Schiff’s bases have been found in floral absolutes,
should not therefore come as a complete surprise. It has been suggested
that if the synthetic fragrance compound is added in to the aromatic plant
material during manufacture, the added material will “blend in”
better. In other instances, absolutes may well contain perfume bases or
reconstitutions, rather than a single key character compound.
Adulteration: the purposeful addition of cheaper alternative oils, oil
fractions, by-products, isolates, natural or non-natural synthetics etc.,
to reduce the cost price of the oil.
Extending: a term for adulteration almost implying a degree of legitimacy.
Isolate: a specific fraction of an essential oil. May be composed of
a single chemical e.g. eugenol from Clove oil.
Organic oil: a more expensive essential oil, which has been derived from
vegetable matter which has been grown in a pesticide free environment,
but which still liable to have a pesticide content reflecting background
Reconstituted oil: An oil made from nature identical synthetics, to look
like analytically as far as possible -, and to give an accurate odour
impression of -, the named essential oil.
Arctander S. (1960) Perfume and Flavour Materials of Natural Origin publ.
Boelens M. (1997) "Differences in chemical and sensory properties
of orange flower and rose oils from hydrodistillation and from supercritical
CO2 extraction" Perf & Flav. 22, May/June 1997 p31.
Garnero J. et al. (1978) Riv. It. Epos. 60, 99.
Health Which February 2001 pp 18-20.
Jones, L. (1998) “Establishing standards for essential oils and
analytical standards” Proceedings of NAHA The World of Aromatherapy
II International Conference and Trade Show St. Louis, Missouri, Sept 25-28,
Nour-el-Din H., Osman A. E., Higazy S. et al. 1977. Egyptian Journal of
Food Science 5(1/2): 67-77.
Singhal RS, Kulkarni PR, Rege DV 2001. “Quality indices for spice
essential oils”. In Handbook of Herbs and Spices. ed. KV Peter,
CRC Press, Woodhead Publishing 2001.