title: Flow injection small-volume fiber-optic pH sensor based on evanescent wave excitation and fluorescence determination.
abstract: A small-volume fiber-optic pH sensor (FOEWS) based on evanescent wave excitation is developed and evaluated. The sensor is simply fabricated by inserting a decladded optical fiber into a transparent capillary tube. A microchannel between the optical fiber and the capillary inner wall was formed and acted as flow cell for solution flowing through. The pH-sensitive fluorophore of fluorescein can be excited by the evanescent wave field produced on the fiber core surface to produce emission fluorescence. pH value was then sensed by its enhancing effect on the emission fluorescence intensity. The response range of the sensor is from pH 2.09 to pH 8.85 and the linear range is from pH 3.25 to 8.85. The proposed sensor has a small detection volume of 2.5 μL and a short response time of 8 s. It has been applied to measure pH values of real water samples and was in good agreement with the results obtained by commercial pH meter.
authors.affiliation: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiong
authors.forename: Ying
authors.initials: Y
authors.lastname: Huang
authors.forename: Zhongbin
authors.initials: Z
authors.lastname: Ye
authors.forename: Yafeng
authors.initials: Y
authors.lastname: Guan
mesh_terms: D004867:Equipment Design; D005336:Fiber Optic Technology / Q000379:methods*; D019793:Fluorescein; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D044085:Microfluidics; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D019793:Fluorescein