PHYSIOLOGICAL PH FIBEROPTIC CHEMICAL SENSOR BASED ON ENERGY-TRANSFER

A fiber-optic sensor has been developed containing a fluorophore, eosin, and an absorber, phenol red, coimmobilized on the distal end of an optical fiber. When an argon laser is used to excite eosin with light of .lambda. 488 nm, a region of the spectrum where phenol red does not absorb, eosin emits light in a spectral region that overlaps significantly with the absorption spectrum of the basic form of phenol red. Consequently, nonradiative energy transfer occurs from eosin (donor) to phenol red (acceptor). The amount of energy transfer increases as the pH increases resulting in a diminished fluorescence intensity. Thus, changes in the absorption of phenol red as a function of pH are detected as changes in the fluorescent signal. In this manner a pH sensor optimized for physiological pH measurement has been prepared. The fiber exhibits a precision of at least 0.01 pH units.