Optical Sensors for Direct Measurements in Chemical Processes

The benefit of employing continuous, and ideally, non-destructive analysis during chemical manufacturing processes is widely recognized as providing very high rates of return to industry. As markets become increasingly more competitive, feedstocks more costly, and environmental issues escalate, the need for robust, stable, and affordable on-line process analysis systems continues to grow. Among the possible technologies employed in these process applications, optical methods are frequently used. The University of Washington Center for Process Analytical Chemistry (CPAC) has had a core effort in the investigation of sensor systems based on optical waveguide technology since its founding in 1984. These efforts have been broadly based, involving both the use of non-invasive direct optical analysis for species or parameter identification and the investigation of minimally invasive extractive approaches utilizing reagent chemistries. This work is further leveraged through strong interactions with another core CPAC program focusing on the development and use of chemometric multivatiate data analysis techniques. The three examples presented below: fiber optic evanescent wave spectroscopy using extractive coatings, the use of integrated grating and waveguide structures, and applications of low coherence high precision reflectometry for process monitoring, represent on-going optical sensor work at CPAC and demonstrate the synergy between this program and chemometrics.