Chemistry Reference
In-Depth Information
react with 1,10-phenanthroline to yield a chemiluminescent signal. An ammonia
imprinted polymer was coated on the surface of a semiconductor to discriminate
ammonia and trimethyamine (Nickel et al. 2001). The bare Cd-Se surface displayed
a similar photoluminescent enhancement with the addition of ammonia and mono-,
di-, and trimethyamine. However, a selective response for ammonia was observed
when the Cd-Se surface was coated with the ammonia imprinted PAA film.
15.5.5. Electrometrical MIP Sensors
Electrometrical transducers that have been utilized for the preparation of MIP-based
chemical sensors can be classified as amperometric (monitor the current at a fixed
voltage), potentiometric (monitor the voltage at zero current), or conductometric
(measure conductivity or impedance changes; Piletsky et al. 2002; Blanco-Lopez
et al. 2004). Amperometric sensors measure the current flowing between a counter-
electrode and a working electrode that is coated with the recognition element.
They have the advantages of simplicity, ease of production, and low cost and are con-
sidered the most popular electrochemical sensor format. An early example of an
amperometric morphine sensor for a competitive format was constructed in 1995
based on a morphine imprinted MAA/EGDMA copolymer (Kriz and Mosbach
1995). Morphine in the concentration range of 0.1-10 pg/ml could be detected by
the amperometric sensor based on competitive binding (Fig. 15.9). This ampero-
metric sensor demonstrates autoclave compatibility, long-term stability, and resist-
ance to harsh chemical environments, although the response of the sensor was
slow, which was due to the time required for equilibration. For nonelectrochemical
active species, amperometric sensors are used for detection through a displacement
Figure 15.9 Competitive morphine sensor response as a function of the morphine concen-
tration (0-10 mg/mL) present in the solution. Three sensor types were examined: morphine
molecular imprinted polymer (M-MIP), reference (O-MIP), and agarose-covered platinum
electrode (Pt-Ag). Reprinted from Kriz and Mosbach (1995). Copyright 1995 Elsevier Science.
