Instant Notes: Analytical Chemistry

Section H – Sensors, automation and computing

H1 CHEMICAL SENSORS AND

BIOSENSORS

Sensors Sensors are small or miniaturized devices designed for the continuous moni-
toring of the physicochemical or biochemical properties of specific analytes so as
to provide qualitative and/or quantitative analytical data. They comprise a thin
layer of a chemically or biochemically sensitive substance (matrix and recogni-
tion element) in contact with a transducer (i.e. a means of converting the chem-
ical or biochemical information into an electrical or optical signal) (Fig. 1). The
transducer signal is then processed by suitable electronic circuitry incorporated
into the device.
Chemical sensorsreact to the presence and concentration of an analyte by
responding selectively to an electrical, optical, thermal or other property.
Biosensorsgenerally employ a thin layer of a substance incorporating an immo-
bilized reagentthat contains biorecognition sites. The biomolecules may be
proteins, often enzymes, or other macromolecules that display specific inter-
actions with an analyte species. Reagents are immobilized by entrapment or

Key Notes

Sensors are devices that respond to the presence of one or more analytes

enabling qualitative and/or quantitative information to be obtained

quickly and continuously.

Electrochemical sensors are based on potentiometric, amperometric or

conductimetric cells that generate signals from electrochemical reactions

of the analyte or in response to the presence of particular chemical

species related to it.

Optical sensors respond to the absorption or fluorescent emission of

electromagnetic radiation by analytes, indicators or analyte−receptor

complexes at characteristic wavelengths, principally in the visible region,

but also in the ultraviolet and near infrared spectral regions.

Thermal sensors measure heats of reaction generated by the oxidation of

an analyte or its reaction with a reagent. Mass sensitive sensors are

mechano-acoustic devices based on piezoelectric effects caused by the

adsorption of analytes onto a crystal surface.

These are groups of sensors that allow simultaneous monitoring with

different instrumental parameters so as to improve the selectivity of the

system for a particular analyte or to monitor several analytes.

Related topics Potentiometry (C3) Ultraviolet and visible molecular

Voltammetry and amperometry (C9) spectrometry: applications (E9)

Conductimetry (C10) Evolved gas analysis (G4)

Sensors

Electrochemical

sensors

Optical sensors

Thermal- and

mass-sensitive

sensors

Sensor arrays