ENHANCED PERFORMANCE OF A FIBEROPTIC LUMINESCENCE CO2 SENSOR USING CARBONIC-ANHYDRASE

Incorporation of carbonic anhydrase into the indicator layer placed at the distal end of an optical fibre has yielded a fast-responding luminescence sensor for carbon dioxide in the gas phase. The measuring principle rests on a CO2-modulated proton transfer from the inner phosphate buffer molecules to photoexcited tris[2-(2-pyrazinyl)thiazole]ruthenium(II) cation, immobilized onto an anionic dextran gel. The best performance of the optical del ice is discussed in terms of internal buffer pH, enzymatic activity and temperature of operation. Optimization of such parameters yields values of 8.5, 4500 U ml(-1) and 20-25 degrees C, respectively. Under these conditions, the fibre-optic sensor is able to respond in 40 s (t(90)) to a 0-100% CO2 concentration change, and in 2 min (t(90)) to a reverse 100-0% CO2 dose variation, compared to 2 and 6 min, respectively, for the non-enzymatic device.