On-line optical determination of water in ethanol

摘要

Abstract: An optical sensor for measurement of water in ethanol is presented that is based on a fluorescent solvent polarity probe immobilized on an ion-exchange membrane. The probe responds to changes in solvent polarity of alcohol/water mixtures by both a shift in the fluorescence emission maximum and a change in the fluorescence quantum yield. In this sensor, the analytical information is the relative fluorescence intensity measured at 620 nm (500-nm excitation). The sensor can be applied over the range from pure ethanol to pure water, however, maximum sensitivity is achieved in the range of 80 to 100% ethanol. The response time (t$-90$/) is in the order of 15 s. Given the unique applications of fiber optic sensors (e.g., in remote and fire-proof sensing), the new sensor may be applied for quality control of ethanol in distilleries and anhydrous ethanol production.!6