Portable fibre optic oxygen sensor based on room-temperature phosphorescence lifetime

A portable fibre optic instrument for oxygen sensing based on luminescence lifetime is presented. The instrument is based on measurement of the quench ing by oxygen of the room temperature phosphorescence (RTP) emitted by alum inium tris(8-hydroxy-7-iodo-5-quinolinesulfonic acid) chelate incorporated in an inorganic matrix by sol-gel technology. The comparatively long RTP li fetime of this sensing material (450 mu s) and the large singlet-triplet sp litting (lambda(exc) 390 nm, lambda(em) 590 nm) allow the use of simple opt o-electronic circuits and low-cost processing electronics. Standard electro nic components have been applied in development of the low-cost lifetime-me asurement instrumentation presented here. Two optical sensor configurations , "flow-through cell" and "probe", have been designed and evaluated for the determination of very low levels of oxygen, in gaseous argon streams and i n waters. The basic technology, design parameters and performance character istics of the optical sensors are discussed. Applications to determination of dissolved oxygen in river, tap and sewage waters are described. The adva ntages of luminescence lifetime measurements over conventional RTP intensit y measurements for oxygen sensing are discussed.