ABSORPTION-BASED SENSORS

Many chemical sensors based on fiber optics and absorption spectroscop y have been reported in applications ranging from biomedical and envir onmental monitoring to industrial process control. In these diverse ap plications, the analyte can be probed directly, by measuring its intri nsic absorption, or by incorporating some transduction mechanism such as a reagent chemistry to enhance sensitivity and selectivity. Physica l and performance requirements are placed on a device depending on its intended use. In applications such as chemical process monitoring, su rvivability and the assurance of the long-term quality of the analytic al data are paramount. The above needs have resulted in devices that n ow employ multivariate data analysis, complex sampling interfaces, and reagent renewal mechanisms. The response from such systems can provid e information not only about target analyte(s), but can also signal th e presence of interferences, and may potentially be used to follow ser ,sor degradation. Examples are given of devices currently being invest igated along with a discussion of some of the remaining material, chem ical, and optical challenges.