Plastic Antibodies - Designing Receptors for the Next Generation of Biosensors - page 112

Fig. 4 Separation of ropivacaine and propranolol enantiomers in CEC by the partial filling
technique using a plug composed of S -ropivacaine MIP and S -propranolol MIP. Detection was
performed at 214 ( top ) and 195 nm ( bottom ). For experimental details refer to [ 59 ]. Reprinted with
permission from [ 59 ]. Copyright (2003) American Chemical Society

However, in the case of multi-template imprinting, the amount of S -propranolol
used in the nanoparticles synthesis strongly affected the recognition performance
for S -ropivacaine. The 1:80 template-to-monomer ratio was found to be optimal to
obtain MIP nanoparticles with twofold selectivity. Priego-Capote and coauthors
have used modified mini-emulsion polymerization to prepare MIP NPs with bind-
ing sites located mainly onto the surface of the nanoparticles [ 61 ]. This in theory
should improve mass transfer of the analytes and reduce peak tailing in CEC. The
synthesized MIP nanoparticles were able to bind threefold more template than the
non-imprinted ones. When tested in CEC analysis a racemic mixture of the template
was separated without evident peak tailing. However the affinity for the template
demonstrated by the novel MIPs was much lower than that obtained through other
polymerization methods (e.g., precipitation polymerization). In addition the size of
the particles obtained was not uniform, ranging from 30 to 150 nm. Qu and
coauthors have used magnetic MIP NPs in a microfluidic CEC device for resolution
of racemic ofloxacin [ 80 , 81 ]. The MIP NPs were pumped into the capillary as a
slurry and packed in the microfluidic device in a specific region next to magnets. In
optimal conditions, a resolution value of 1.46 was achieved in slightly more than
3 min of analysis. This approach seems really promising for a fast and cheap
qualitative analysis. The detection limits (5 M for the template S -ofloxacin, and

m

1 M for R -ofloxacin), however, were too high compared to conventional chro-

matographic methods, and hence system required further improvement.

m