Heavy-atom induced room-temperature phosphorescence: a straightforward methodology for the determination of organic compounds in solution

Abstract

We present here the first confirmation that the new methodology of room-temperature phosphorescence emission named heavy-atom induced room-temperature phosphorescence (HAI-RTP), can be observed for both polycyclic aromatic hydrocarbons and nitrogen heterocycles. This methodology makes use of RTP emission directly from the analyte in fluid solution, without a protective medium but only with the presence of high concentrations of heavy atom perturbers. This permits a sufficient interaction between the perturbers and the analytes to produce effective population of their triplet states, and consequently, an intense phosphorescent emission. Good deoxygenation conditions are obtained using sodium sulfite as the oxygen scavenger. In order to confirm this new phosphorescence methodology, a wide variety of compounds, with different chemical structure, have been selected. In this work, polycyclic aromatic hydrocarbons as naphthalene derivatives (naphthylacetic acid, α-naphthalene acetamide, naproxen, nafronyl, dansylamide and carbaryl) and fluorene and several nitrogen heterocyclic compounds as benzimidazole derivatives (thiabendazole), carbazole, indole derivatives (tryptamine, tryptophan and indole-3-butyric acid) and an acridine derivative (9-hydroxy-4-methoxyacridine), have been studied. Phosphorescence spectral characteristics of these compounds (excitation and emission wavelengths and lifetime) and the optimization of the chemical variables involved in the phosphorescence phenomenon in solution, are reported. Under optimal experimental conditions, calibration graphs and detection limit in the ng ml −1 level, have been established.