Abstract :
[en] Headspace solid-phase microextraction (HS-SPME) is an easy, effective, and selective technique for the
extraction of volatiles and semi-volatiles compounds. For the latter, longer equilibration times are
needed, which are typically shortened by applying agitation or heating the sample. A less explored way
to improve the extraction kinetics of analytes with a low-affinity for the headspace is to sample under
vacuum conditions. The methodology that evolved from this approach was termed “vacuum-assisted HSSPME”
(VaceHSeSPME) and was mainly used for water- and solid-based samples.
The aim of this work was to investigate the effect of vacuum when dealing with non-aqueous liquid
samples. For this purpose, the volatile profile of extra virgin olive oil was analyzed using a divinylbenzene/
carboxen/polydimethylsiloxane fiber followed by gas chromatography-mass spectrometry. The
effects of extraction temperature and sampling time were investigated using traditional one-variable at a
time approach and a two-variable central component design for both VaceHSeSPME and regular HSSPME.
The results showed an important enhancement in the extraction of semi-volatile compounds
when using VaceHSeSPME, and improved the information gained for the olive oil aroma fingerprint. A
theoretical formulation of the underlying process was proposed, providing new insights into the SPME
extraction theory. Lowering the sampling pressure effectively reduced gas-sided limitations and accelerated
extraction kinetics. However, for viscous samples such as olive oils, the liquid-phase resistance
played an important role and delayed extraction. Overall, applying heating (i.e. reducing the viscosity of
the oily sample and increasing headspace concentrations) next to reducing the total pressure in the
headspace is the best analytical HS-SPME strategy for obtaining fast a rich volatile profile from the oily
samples.
Name of the research project :
PortASAP - European network for the promotion of portable, affordable and simple analytical platforms
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