ABSORPTION-BASED SENSORS

Many chemical sensors based on fiber optics and absorption spectroscopy have been reported in applications ranging from biomedical and environmental monitoring to industrial process control. In these diverse applications, the analyte can be probed directly, by measuring its intrinsic absorption, or by incorporating some transduction mechanism such as a reagent chemistry to enhance sensitivity and selectivity. Physical and performance requirements are placed on a device depending on its intended use. In applications such as chemical process monitoring, survivability and the assurance of the long-term quality of the analytical data are paramount. The above needs have resulted in devices that now employ multivariate data analysis, complex sampling interfaces, and reagent renewal mechanisms. The response from such systems can provide information not only about target analyte(s), but can also signal the presence of interferences, and may potentially be used to follow ser,sor degradation. Examples are given of devices currently being investigated along with a discussion of some of the remaining material, chemical, and optical challenges.