Biomedical Engineering Reference
In-Depth Information
Figure 9.8
Effect of pH on
K
d
values, measured in HNO
3
-
spiked unfi ltered river water [liquid/solid ratio (L/S) = 10
5
].
Reprinted with permission from Ref. [7];
© The American Chemical Society.
materials fall well outside the size range that is traditionally considered a nano-
material (i.e., their sizes are
100 nm) [20]. In addition to magnetic nanoparticles,
a great deal of attention has been paid to nanoporous materials such as silica
ceramics (pore sizes
>
3-6 nm, but particle size on the order of microns) for the
removal and remediation of contaminants from natural waters due to their high
surface area and relative ease of functionalization [7, 19, 115-117]. However,
although these materials serve as outstanding sorbents for contaminants, they
suffer from intrinsic mass transport limitations of moving large volumes of water
to the sorbent material. Alternatively, other high-surface-area sorbents that can be
surface functionalized and are more readily dispersible in aqueous systems, yet
can be easily recovered once bound to the target analyte, offer signifi cant advan-
tages for many applications. Materials such as magnetic nanoparticles [7] and
polymer/nanoparticle composites [118-121] offer unique capabilities for magneti-
cally directed separation and sensing processes.
∼
9.3.3
Electrochemical Detection Enhanced by Magnetic Nanomaterials
for Preconcentration
Sorbent materials of all types play a role in the binding, separation, and removal
of target analytes from complex samples, and may also enable enhancements in
the limits of detection for a wide range of sensor systems. Primarily, magnetic
nanoparticles have been used in a preconcentration capacity in electrochemical
