Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

9 SOLID PHASE MICRO-EXTRACTION AND HEADSPACE TRAPPING EXTRACTION
However, static headspace samples are normally too small to
quantify odorants that are present only at low concentrations in the vapor
phase. In other words, one can smell them, but in many cases it is not possible
to obtain a signal in a mass spectrometer.
9.7.2 Dynamic Headspace Trapping
To overcome the disadvantages of headspace trapping method,
dynamic headspace trapping can be used (Figure 6). Again, the food sample
is placed in a heated vessel but the evaporating compounds are continuously
swept by a stream of inert gas into a trap containing a porous polymer,
which adsorbs more or less the organic constituents. This method yields a
much higher amount of trapped volatiles so that, after desorption, it is no
longer problematic to obtain an MS signal.
Figure 6: Dynamic headspace trapping technique
However, the disadvantage of this procedure is the strong dependence
on the yield of the odorants, on the velocity of the carrier gas and
on the selectivity of the adsorption and desorption process for different
compounds. It is very diffi cult to control these parameters precisely and
therefore, the results of such quantitative measurements might be inaccurate.
9.7.3 Recovering the Adsorbed Volatiles by Thermal or
Liquid Solvent Desorption
Several studies have reported methods of desorption using organic
solvents. Drawbacks of the use of solvent desorption include the loss
of volatile compounds during removal of excess solvent before GC analysis,
solvent selectivity and solvent impurities. We recently developed a sensitive
and highly reproducible dynamic headspace (DHS) protocol with thermal
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