Flow through optical sensors for ammonia and carbon dioxide and determination of ammonia in physiological and bioreactor samples

The goal of this research project is to develop a series of flow through fiber-optic sensors for ammonia and carbon dioxide. Fiber-optic ammonia sensors are designed to measure ammonia levels in rat hippocampus perfusates and mammalian cell bioreactor samples.;Flow through fiber-optic sensors are constructed using two types of indicator immobilization techniques. In both cases, the gaseous analyte (ammonia or carbon dioxide) diffuses across the membrane and reacts with the indicator. Absorbance or reflectance of the immobilized indicator is measured through a fiber-optic probe and related to analyte concentration.;In the first case, a fiber-optic sensor is designed for measuring ammonia levels in rat hippocampus tissue extracellular fluid. Bromothymol blue is dissolved in an aqueous solution and trapped behind a microporous Teflon membrane. The resulting sensor possesses a dynamic range of 0.2 to 20 ;In the second case, a flow through fiber-optic sensor is constructed by immobilizing chlorophenol red along the inner walls of the pores of a microporous polypropylene membrane. This sensor is designed to measure ammonia levels in 10 ;A solid-state fiber-optic gas sensor is also described for carbon dioxide. Here, ion-pairs of cresol red and phenol red and a quaternary ammonium cation are adsorbed along the pore walls of a microporous Teflon membrane. The weak acid, carbon dioxide, diffuses into the gas permeable membrane and reacts with the indicator-quaternary ammonium ion-pair. The resulting change in reflectance is monitored with a fiber-optic probe.