Nanotechnology-Enabled Sensors

3.4 Electrical Transducers
Fig. 3.16 An ion selective electrode with an external reference electrode.
ISEs play an important role in diagnostic medical sciences. Four of the
chemical components in chem-7 tests are analyzed with ion selective electrodes.
9 In this monitoring process, which represents a large number of
common hospital laboratories tests, Na + , K + , Cl – , CO2, glucose, urea, and
creatinine are measured. No electrode responds selectively to only one
kind of ion; however, some are fairly selective. For instance, the glass pH
electrode is among the most selective membranes to hydrogen ions. In this
case, sodium ions are the main interfering species, limiting th practical applications
of pH measurements.
ISEs can be categorized to four different types, depending on the material
of the membrane:
Glass membrane: It is used for measuring ions such as Na + or measuring
pH. Glass membrane electrodes are generally formed by chemically doping
a silicon dioxide glass matrix. The most common glass membrane
electrodes are the pH electrodes.
Solid-state membranes: They are used for measuring ions such as Pb 2+ .
Solid-state electrodes are made of relatively insoluble inorganic materials
within a membrane. Other ions, which can be measured, include cupric,
cyanide, thiocyanate, chloride and fluoride, etc.
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