Room-temperature phosphorescence fiber-optic instrumentation for simultaneous multiposition analysis of dissolved oxygen

Abstract

The design and analytical characterization of a fiber-optic instrument for simultaneous multiposition water-dissolved oxygen monitoring by room-temperature phosphorescence (RTP) measurements is presented. The sensing principle is based on the RTP quenching by oxygen of the phosphorescent light emitted by the metal chelate formed by Al with 8-hydroxy-7-iodo-5-quinolinesulfonic acid (Al-ferron) trapped in a sol–gel solid support. Four RTP oxygen sensor flow-cells are assembled in order to measure the oxygen content in four different water streams. A xenon flash-lamp is used as the single excitation source for the four sensing regions, while multichannel phosphorescence detection is achieved by using a cooled intensified charge-coupled device (ICCD). Four bifurcated optical fibers are used to carry the light from the excitation source to the sensing active surface in the flow-cell and to bring the emitted RTP to the detector. The RTP light coming from each of the optical fibers was focused onto different sites (rows of pixels) of the ICCD. In this way, the RTP signals from each of the four sensing materials packed in the flow-cells can be differentiated and measured. Simultaneous dissolved oxygen monitoring in several water streams containing different dissolved oxygen levels is demonstrated by using the proposed instrumentation. Also, the relatively long phosphorescence lifetime of the materials used allow the use of the developed instrumentation to perform lifetime room-temperature phosphorescence measurements.