FIBEROPTIC PH-METER USING NIR DYE

An absorption-based, fiber-optic pH meter for the physiological pH range is presented. It employs a sensor membrane based on a NIR proton-carrier dye and laser diodes as light sources. It is shown that an optical absorption sensor with a sensor dye placed on the tip of a bifurcated fiber requires special provisions to receive sufficient light back from the sensor head to the detector. With respect to available cheap and intensive light sources in the NIR, it is advantageous to use NIR dyes for chemical sensor membranes. A new type of acidochrome dye immobilized in a PVC matrix is presented for use with a two-wavelength, single-beam fiber-optic photometer. The scopes and limitations of the optical design of this photometer are discussed. pH values measured with the fiber-optic pH meter are compared with the results obtained with a glass electrode.