MEASUREMENT OF SODIUM-HYDROXIDE CONCENTRATION WITH A RENEWABLE REAGENT-BASED FIBEROPTIC SENSOR

A fiber-optic caustic sensor Is described In which a weakly buffered acid-base Indicator reagent (bromothymol blue) is continuously delivered to the sensor tip which consists of a length of Nation hollow fiber membrane, an analyte exchange region, and an optical cell. In this study, caustic concentrations of 1.5-23.0% (w/w) (0.38-7.2 M) were measured, with a relative standard deviation of 1.6%. Sensor performance was studied at several reagent compositions, at various reagent delivery rates, In the presence of brine, and with respect to probe-to-probe reproducibility and long-term use. This technique, of controlled reagent phase renewal, successfully addresses several of the limitations of previous reagent-based fiber-optic sensors. In addition, many new opportunities are created when considering the flexibility of such sensors, such as the ability to use multiple reagents and Irreversible chemistries. © 1990, American Chemical Society. All rights reserved.