A REVERSIBLE OPTODE MEMBRANE FOR PICRIC ACID-BASED ON THE FLUORESCENCE QUENCHING OF PYRENE

Pyrene immobilized in plasticized poly(vinyl chloride) (PVC) membrane is able to extract selectively picric acid from the sample solution in to the organic membrane phase. Since this extraction equilibrium is ac companied by a change in the fluorescence spectrum of pyrene, the chem ical recognition process can be directly translated into an optical si gnal. With the optode membrane described, picric acid in sample soluti ons from 8.7 x 10(-6) to 4.3 x 10(-3)M can be determined. The calibrat ion curve of the optode membrane for picric acid shows a good correlat ion with the mathematically derived formalism and thus confirms the th eoretically expected behaviour. Besides a high reproducibility of the optical signals, the very short response times less than 35 sec are re alized. The optode membrane presented exhibits good selectivity for pi cric acid over many other usual hydrophobic anions.