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Using Gas Chromatography to Evaluate Essential Oil Quality

Chromatographs (gas chromatography) show the relative amounts of the various organic components that make up essential oils. The primary types of components include:

Component Therapeutic Action Toxicity / Skin Irritation
Alcohols Antiseptic, antiviral, bactericidal Low
Aldehydes Antifungal, anti-inflammatory, disinfectant, sedative Moderate
Esters Antifungal, antimicrobial, sedative, antispasmodic Low
Ketones Anticatarrhal, cell proliferate, expectorant, vulnerary High
Lactones Anti-inflammatory, antiphlogistic, expectorant, febrefuge Moderate to High
Oxides Expectorant Moderate
Phenols Antiseptic, bactericidal, disinfectant, stimulant Moderate to High
Terpenes Anti-inflammatory, antiseptic, antiviral, antibacterial,
(some are analgesic or stimulant)
Generally Low

In simple terms, when choosing an essential oil, one wants high therapeutic value and low toxicity. There are many different compounds within each of the major categories - altogether there are several hundred individual chemical substances that are found in essential oils. This makes it difficult to evaluate oils chemically. Even though a chromatograph may show only a few of the constituents of an oil, one still needs knowledge of many individual substances and their properties to read a chromatograph.

However, an illustration will show some of the basics:

Below are two chromatographs (with reports) - one is for Lavender Provence and one is for Lavender Dalmatian. I prefer the Lavender Provence (which is what we sell). Here is why:

A "good" Lavender contains a high proportion of esters and alcohols and a low proportion of camphor. The esters are especially prized in Lavender. "The constituents of different species differ in their content of the ester, linalyl acetate due to altitude. If lavender is grown above 2,000 feet, the ester content is increased, producing a more valuable oil." - quoted from the textbook for Aromatherapy Certification of the Australasian College of Herbal Studies.

Both the Provence and Dalmatian Lavenders are high in Linalool - a terpenoid alcohol that is low in toxicity and has good antiviral and antibacterial properties. Both are also low in camphor, which is a ketone and therefore a strong irritant. However even a quick glance at the charts shows that the Lavender from Provence is MUCH higher in Linalyl Acetate, an ester which is very low in toxicity and is highly valued for it's therapeutic effects. It is Linalyl Acetate which gives Lavender its' famous calming properties. Therefore, while either of these lavenders will have good antiviral and antibacterial properties, the Lavender Provence has outstanding calming and antispasmodic properties whereas the Lavender Dalmatian will have a less calming effect.

Lavender Provence (organic)

GC-MS Analysis Report
Peak Area Peak Time Peak Scan Marker Text
1.064 0:16:06 357 Pinene or Beta-Myrcene
7.432 0:17:04 414 Ecalyptol; 1:8 Cineole
31.909 0:18:07 475 Linalool
7.518 0:19:07 534 Camphor
3.282 0:19:35 561 Borneol
5.317 0:19:43 569 CAS 562-74-3
27.504 0:20:46 630 Linalyl Acetate
3.585 0:21:14 657 Geraniol Acetate
1.362 0:23:58 817 Farnesene
1.085 0:24:01 820 Caryophylene

Instrument: VG70E
Notes: MS/LB CB5 50m 1.2u 40(5)>250@10 10m/m spli 10psi inj 220 - 1.2x10-6 - 10mg in 1ml DCM 1ul inj

Lavender Dalmation

GC-MS Analysis Report
Peak Area Peak Time Peak Scan Marker Text
0.571 0:15:57 578 a-Pinene
3.404 0:17:40 678 Ocimene Isomer
0.732 0:17:50 688 d-Limonene
7.369 0:17:54 692 Eucalyptol
40.241 0:18:52 748 Linalool
1.952 0:20:03 817 Camphor
1.453 0:20:21 834 Hexyl Butanoate
7.234 0:20:32 845 endo-Borneol
7.084 0:20:38 850 Terpinen-4-ol
6.281 0:21:31 902 Linalyl Acetate
0.850 0:22:00 930 Lavandulyl Acetate
2.713 0:24:47 1091 b-Farnesene

Instrument: VG70E
Notes: MS/LB CB5 50m 1.2u 40(4)>250@10 30m/m spli 15psi inj 250 - 1.2x10-6 16.3mg