A RECIRCULATING-FLOW FLUORESCENT OXYGEN SENSOR

An immersible oxygen sensor was constructed by circulating small quant ities of ruthenium tris-(2,2'-bipyridyl) II dichloride oxygen-sensitiv e fluorescent dye through a loop of oxygen-permeable silicone tubing i mmersed in test medium. The fluroescence intensity of the dye was subs equently measured as it exited the flow loop and related to oxygen ten sion. This method of measuring the oxygen tension, through diffusive t ransport to a flowing stream of dye and recirculating it in the sensor , has been found to give a stable response and relatively long sensor lifetime without major recalibration. The sensor showed good stability over at least a week's duration and showed no degradation due to leac hing of the dye through membranes or photobleaching that commonly affe cts fluorescent sensors with immobilized chemistries. (C) 1996 Elsevie r Science Limited