Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

9 SOLID PHASE MICRO-EXTRACTION AND HEADSPACE TRAPPING EXTRACTION
9.4.1 History of Headspace
In November 1986, at the 10th International Congress on Essential
Oils, in Washington DC, USA, Dr. B. D. Mookherjee presented a paper
on the impact of “live vs. dead” on headspace trapping extraction, using as
example jasmine fl owers.
The SPME needle which is 2- to 3-mm solid glass fi ber coated
with a high-boiling liquid adsorbent, is placed in close proximity to a fl ower
without touching it and is kept there for a period of 30-60 min depending
on the odor strength of the blossom. The aroma molecules around the petals
are absorbed onto the fi ber. Then with GC/MS, the fi ber is analyzed to
determine the aroma profi le of that particular fl ower. The aroma of the living
fl ower was brought into space by NASA in 1998.
9.4.2 The Aura
When the Sun is totally eclipsed by the moon, the surrounding
glow is called an aura. Similarly, if we consider a drop of fragrance, the molecules
surrounding the drop form an aura of that particular fragrance.
It is a common belief that one smells a fragrance, layer by layer,
from the top note of the volatile components, to the middle note of components
with boiling points in the middle range, and fi nally to the bottom note
of components with the highest boiling point.
In reality, when a drop of fragrance is placed on the skin, several
different molecules, from the lowest to the highest boiling types, irrespective
of their molecular weights, boiling points and vapor pressures, form
an aura, which eventually reaches our nose and gives us our fi rst impression
of the particular fragrance. The composition of this aura depends on a characteristic
property of each fragrance molecule, knows as its diffusivity.
9.4.3 What is Diffusivity?
Diffusivity is the inherent property of a compound to emit its
molecules into the air. One compound is said to be more diffusive than another
if its molecules tend to pass into the air to a greater extent than those
of other compounds. Diffusivity is independent of boiling point, molecular
weight, odor threshold or odor value.
9.4.4 Application of Headspace Trapping
Some examples of headspace trapping are discussed here.
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