New microsensors and their use in marine research

Bo Barker Jorgensen, Ph.D.
Max Plank Institute at Bremen

Friday, January 29, 1999
12:00 Noon—Pacific Forum

Microsensors are measuring instruments with tip diameters of 1-20 µm, 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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