Page 112 - Academic Press Encyclopedia of Physical Science and Technology 3rd BioTechnology

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Encyclopedia of Physical Science and Technology EN005F-954 June 15, 2001 20:48

Fiber-Optic Chemical Sensors 825

FIGURE 19 Fluorescence image of a DNA sensor array with ∼13,000 DNA probe regions.

have also been developed. For detecting volatile organic a pH-sensitive dye. The formation of acetic acid, which is
compounds, direct fluorescence spectroscopy can be one of the enzymatic reaction products, changes the local
used since most volatile organic compounds have unique pH and thereby the fluorescence signal. The inhibition of
fluorescence spectra. Moreover, by using time-resolved this reaction can be related to the pesticide concentration
fluorescence spectroscopy, it is possible to distinguish in the sample.
between volatile organics with similar structures, for Current research activities on environmental fiber-optic
example, toluene and benzene. Heavy-metal fiber-optic chemical sensors are focused on developing multianalyte
chemical sensors are mostly based on ion sensitive sensors for on-line and in situ monitoring. These sensors
indicators as described in Section III.B.1.c. may one day be used as environmental warning devices
Pesticides are another important group of pollutants that that will help prevent environmental catastrophes by trig-
can be detected by fiber-optic chemical sensors. Since pes- gering an alarm whenever uncontrolled release of pollu-
ticides are designed to interact with biological molecules, tants to the environment occurs.
fiber-optic biosensors are mostly used for their detec-
tion. One example is the detection of organophosphate
C. Industrial and Bioprocess
and carbamate pesticides by monitoring their inhibition
Control Applications
effect on the enzymatic reaction of acetylcholinesterase
(AChE) with its substrate, acetylcholine. The enzyme is In the chemical and bioprocess industries, the need for
coimmobilized at the distal end of the fiber together with real-time process and quality control has elicited a great