A compact, in-situ, spectrophotometric sensor for aqueous environments: design and applications

A compact, portable and sensitive instrument has been designed and built for in-situ spectrophotometric analyses on aqueous solutions. This sensor, known as the spectral elemental analysis system (SEAS), has been successfully used for nutrient and pH measurements on both autonomous underwater vehicles (AUVs) and on moored platforms. The key element of SEAS is a liquid-core waveguide made of Teflon AF-2400 that permits long optical path lengths (several meters) in a very small volume (/spl sim/40 cm/sup 3/). Using SEAS, sub-nanomolar detection limits have been achieved for a wide variety of analyses. A unique feature of SEAS is the minimal reconfiguration required to perform fluorimetric analyses. Characteristics of the SEAS instrument are described, including laboratory and field measurements.