OPTICAL-FIBER SENSORS FOR BLOOD-GASES AND PH, BASED ON POROUS-GLASS TIPS

Optical-fibre sensors have been developed for the determination of blo od gases and pH. Chemical binding of pyrenebutyric acid and 7-hydroxy- 4-methylcoumarine-3-acetic acid to a porous tip of a fused silica fibr e produces a sensitive measuring device for molecular oxygen and pH. I nsertion of the pH sensor into a solution of bicarbonate, entrapped wi thin a polypropylene membrane, yields a pCO(2) sensor. Excitation of t he oxygen-sensor tip within the range 340-360 nm yields emission with a maximum intensity at 460 nm. An intensity ratio approximate to 10 be tween signals measured in pure gas-phase nitrogen and oxygen is obtain ed. Excitation of the sensitive tip within the range 360-380 nm yields emission with a maximum intensity at 457 +/- 3 nm. The excitation spe ctrum is red shifted about 19-30 nm relative to that obtained in solut ion. The maximum intensity of the excitation spectrum for the acidic f orm of the bound coumarine derivative is at 356 +/- 3 nm, whereas for the basic form it is at 380 +/- 3 nm. The apparent pK of the bound cou marine derivative is 7.45 +/- 0.30. The bias and the precision for pO( 2) determinations in blood samples are about - 1 and +/- 1.5 torr, res pectively. For pH determinations, the respective values are about 0.02 and 0.04 pH units and for pCO(2) about 1 and 2.5 torr. The sensors de scribed are suited for production on an industrial scale.