New microsensors and their use in marine
Bo Barker Jorgensen, Ph.D.
Max Plank Institute at Bremen
Friday, January 29, 1999
12:00 NoonPacific Forum
Microsensors are measuring instruments with tip diameters of 1-20 Ám, which can be
used for the analysis of chemical and physical parameters in aquatic systems. According to
their basic sensing principle, they are electrochemical, optical or bio-microsensors. Best
known are the Clark-type oxygen microelectrodes, in which oxygen diffuses through a
gas-permeable membrane and is reduced on the catalytic surface of a kathode. According to
a similar principle, gas-microelectrodes have been constructed for hydrogen, nitrous
oxide, hydrogen sulfide and carbon dioxide. Ions can be analyzed by LIX-based (Liquid Ion
exchanger) electrodes or by voltammetric sensors. Optical microsensors made from single,
tapered optical fibers can measure basic optical properties of highly light-scattering and
absorbing materials. Immobilization of specific fluorescent dyes at the fiber tip enables
the measurement of oxygen, pH or temperature.
Very few biomicrosensors have been developed, but these have enabled the first high-
resolution measurements of methane and nitrate in marine environments. Examples will be
given of some of these microsensors, their basic operating principles, and how they may be
applied to study chemical microgradients and microbial processes in marine environments.
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Last updated: December 19, 2000