关键词: 光导纤维, 化学传感器, 氧传感器, 溶解氧

Abstract: A novel circulatory system for on-line monitoring of dissolved oxygen that makes use of a fiber-optic chemical sensor is presented. An oxygen sensitive optode was combined with a membrane onto which was immobilized pyrenebutyric acid as a fluoroprobe, the membrane was composed of cellulose triacetate as a polymer and di-(2-ethyl hexyl)-o-phthalate as a plasticizer. The dissolved oxygen in water was determined via quenching of the fluorescence of pyrenebutyric acid. The optode shows a satisfactory linear response for the dissolved oxygen in water(r=0.9956, n=6). The relative standard deviations were 2.4%～6.1%. The detection limit was 0.03μg/mL(S/N=3). The exposure time and recovery time of the optode membrane are 5s and 25s respectively. The reversibility of the fluorescence signal was evaluated by alternate measurements in air saturated water and nitrogen-purged water. The relative standard deviation(n=6)were found to be 0.7%. The fluorescence intensity of the membrane in contact with flowing water was recorded over a period of 96h. From fluorescence intensity values taken every 4h(n=24)a RSD of 8% was obtained. After 3 month, the fluorescence signal of the membrane had decreased by 14%. The decrease may be due to washing out of fluoroprobe, but this was not an obstacle to its further use; the quantitative information(F₀/F)did not change significantly, where F₀ and F are the fluorescence intensities in the absence and in the presence of oxygen, respectively. The sensor has good reproducibility and long-term stability. The interference was investigated and the selectivity of method in seawater was affirmed by a conventional method.

Key words: fiber optic, chemical sensors, oxygen sensor, dissolved oxygen