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 into the organic membrane phase. Since this extraction equilibrium is accompanied by a change in the fluorescence spectrum of pyrene, the chemical recognition process can be directly translated into an optical signal. With the optode membrane described, picric acid in sample solutions from 8.7 x 10(-6) to 4.3 x 10(-3)M can be determined. The calibration curve of the optode membrane for picric acid shows a good correlation with the mathematically derived formalism and thus confirms the theoretically expected behaviour. Besides a high reproducibility of the optical signals, the very short response times less than 35 sec are realized. The optode membrane presented exhibits good selectivity for picric acid over many other usual hydrophobic anions.