Chemistry Reference
In-Depth Information
(a)
(b)
Sample
Elution
Sample
Elution
Elution
waste
Buffer
200
μ
m
Column
chamber
Separation
waste
Elution
waste
Buffer
Separation
100
μ
m
Figure 17.13
(a) Schematic of the microfluidic layout for the solid phase extraction/separation device with
expanded view of the extraction region of the device. The dotted line signifies the direction of fluid flow during
extraction; the solid line signifies flow during elution/injection. The narrow channels are 55
m
m wide; the
column chamber is 210
m deep. (b) Fabrication of photopolymerized frits:
sporadic polymerization due to siphoning effect (top) and successful fabrication of a usable frit (bottom).
Adapted from [125] © 2005 American Chemical Society.
m
m wide. All channels are 15
m
Photopolymerized frit structure has a main advantage based on the fact that it can be formed anywhere in
a microchannel. For online coupling of SPE with zone electrophoresis on microchip (MCZE), a microfluidic
device with a nanoporous membrane sandwiched between two PDMS substrate has been developed by Long
et al
. [126]. SPE and MCZE can be carried out in upper and lower fluidic layers, respectively. In addition,
Broyles
et al
. [127] have reported a representative work showing the power of the integration filtration,
concentration and separation on microchip has been reported which design is shown in Figure 17.14.
Interestingly, filtration consists of an array of seven thin channels (1
μ
m deep and 18
μ
m wide) which comes
together into one channel (5
m wide). The input of the thin channels is communicated with
sample reservoir and the sample loading was electrokinetically carried out. Sample concentration was
performed by solid phase extraction. The separation channel was coated with C18 (1.5-4
μ
m deep and 25
μ
m) particles. Then,
simply by increasing injection times, the analytes were retained and concentrated in the separation channel,
being afterwards eluted with the appropriate solvent.
Moreover, a monolithic stationary phase synthesized by the polymerization of acrylate monomers for SPE-
MCEC has been reported by Augustin
et al
. [128]. In the monolithic-SPE-MCEC analysis, the 200-fold
enrichment and successive separation of polyaromatic hydrocarbons are accomplished at the sample injection
time of 60 s.
μ
