A new fluorescent sensing membrane for the determination of picric acid based on reversible fluorescence quenching of fluoranthene dissolved in plasticized poly(vinyl chloride) membrane has been developed. The optimum membrane consists of 1-6 mg fluoranthene, 50 mg PVC, 100 mg bis(2-ethylhexyl)phthalate. With the optimum sensing membrane described, picric acid in sample solution from 1.78 ?10-6 mol L-1 to 1.28 ?10-3 mol L-1 can be determine Besides a high reproducibility of the optical signals, the very short response times of less than 30 s are realized. The membrane has good selectivity, many usual hydrophobic anions don't interfere. The proposed method has been applied to indirect determination of cinchonine with satisfactory results.

Key words: POLYVINYL CHLORIDE, FILMS, FLUORESCENCE, FLUORANTHENE, TRINITROPHENOL, QUENCHING