Lanthanide luminescence based probe for detection of picric acid
Europium fluorescence is significantly enhanced through ligand sensitization using aromatic benzene mono and di carboxylic acids as ligands in aqueous solution. By optimizing metal to ligand ratio and solution pH, it is established that the enhancement is maximum with iso-phthalic and tere-phthalic acid. Phosphorescence of isophthalic acid is recorded and its triplet energy level is found to be at 25633 cm-1; just above the fluorescing energy level of Eu3+. On complexation with these ligands though the europium luminescence is enhanced by orders of magnitude, the europium lifetime increased marginally. Addition of picric acid resulted in the quenching of europium luminescence in europium-isophthalic acid complex. Based on this quenching, a fluorimetric method is developed for the estimation of picric acid in aqueous solution. Picric acid in aqueous solution could be estimated down to 0.23 ppm. Common cations and anions found in natural waters did not interfere in the analysis. The precision in measurement is within 5 % RSD in the entire range of measurement.
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