A fibre-optic oxygen sensor based on contact charge-transfer absorption

Abstract

A fibre-optic oxygen (O 2) sensor monitoring at a wavelength of 400 nm has been successfully developed for the determination of gaseous O 2. Its working principle is based on the contact charge-transfer absorption of N, N-dimethyl- p-toluidine and O 2. The response to changes in O 2 concentrations is reversible and in good agreement with the Beer-Lambert law. The response and recovery times are 12 and 26 min, respectively. The sensor can detect a wide range of O 2 concentrations, ranging from 4.3 to 100% O 2. The precision is 1.45% ( n=5) in a gas mixture of 95% O 2 in N 2 and the limit of detection is 4.3% O 2 (3σ b). The sensor is stable with a 0.53% change in sensitivity per hour. There is a 0.25% °C −1 decrease of the sensitivity of the sensor to O 2 in the range 20–34°C. Water vapour and nitrogen dioxide interfere slightly, whereas hydrogen sulphide and hydrogen chloride have moderate interference on the sensor. However, chlorine and sulphur dioxide seriously interfere with the sensor.