Chemistry Reference
In-Depth Information
SPME manual
assembly
Septum-piercing
needle
Headspace
mode
Fibre
Fibre attachment
needle
Sample
Total-immersion
mode
Stirring bar
Figure 17.4
Basic configurations for SPME [7].
selected sorbent. Analyte elution is typically accomplished with 20-50
l of an appropriate solvent, which
can directly be transferred to the GC/LC port. MEPS applications include, for instance, the determination of
PAHs in water [35] and of drugs in blood [36].
Other SPE formats, such as packing in conventional micropipettes or 96-well-plate, although popular in
certain application areas such as high throughput clinical analysis, are still scarcely used in other research
areas, in which they are far from considered really established and accepted configurations.
μ
Solid phase microextraction
Solid phase microextraction (SPME) was introduced in 1990 by Pawliszyn's
group [37] as a (virtually) solvent-free preconcentration technique in which the analyte(s) is (are) adsorbed
onto a fused-silica fibre coated with an appropriate sorbent layer by simple exposure of the fibre for a pre-
selected time to the headspace of the sample or by direct immersion in a liquid sample (Figure 17.4).
Despite been an equilibrium (i.e. non-exhaustive) technique and the initial limitations regarding the nature
of the commercialized sorbent coating, SPME was rapidly accepted as a simple, reproducible, miniaturized
and green technique, and its feasibility for fast and accurate analysis of (semi-)volatile compounds was
illustrated through a number of application studies. Today, on-line coupling of SPME with LC and GC are
achieved goals and a number of systems (e.g. autosamplers) allowing complete automation of the process are
commercially available. Alternative SPME-formats have also been proposed [38, 39] although, in general,
they have achieved only a rather limited success.
