Chemistry Reference
In-Depth Information
100
SBSE
80
SPME
60
40
20
0
1
10
100
1000
10 000
10 0000
K(o/w)
Figure 7.2
Theoretical recoveries of SBSE and SPME. Theoretical recoveries for solutes as a function of the
octanol-water partition coefficient K
(o/w)
for SBSE (10 ml sample, 50
m
l PDMS phase) and SPME (10 ml sample,
0.5
m
l PDMS phase).
Microsyringe
Headspace
Organic solvent drop
Equilibria
Sample
Stirrer
Figure 7.3
SDME setup in headspace mode.
semi-volatile organic compounds. The advantage of HS-SDME over DI-SDME is the better stability of the
solvent drop and that the aqueous sample can be stirred more quickly. Further improvements involve
addressing the problem of solvent evaporation by the use of ionic liquids as the receptor phase [38]. The
factors influencing the analytical parameters of the method are the extraction time, solvent properties, solvent
drop and sample volumes, stirring rate, temperature and ionic strength of sample solution [39].
The main disadvantage of SDME is the instability of the solvent drop during extraction. If the sample
is stirred too vigorously or the syringe is operated by an inexperienced analyst, the drop may be dislodged.
In the case of HS-SDME there is the problem of proper solvent selection. If the solvent is too volatile,
