OPTODE FOR BULK-RESPONSE MEMBRANES

A simple optical sensor based on photodiodes with built-in optical filters is described. The sensor Is used with a new class of optode membranes recently Introduced. These rely on ion extraction Into the bulk of a polymeric membrane and therefore can yield relatively large absorbance changes that can be measured easily. Ambient light, whose intensity is monitored by a reference photodiode, is used as the light source. The membrane is placed directly on top of a second photodiode making the entire device very compact. The performance of the sensor with regard to fluctuations in the irradiation and the determination of nitrate in vegetable extracts, as an example, Is described. © 1990, American Chemical Society. All rights reserved.