Spectrofluorometric determination of carbazole with sodium methoxide and potassium iodide

Abstract

The measurement of the fluorescence intensity of carbazole is interfered with the presence of polynuclear aromatic compounds, such as anthracene and fluoranthene. For the purpose of reducing these interferences, the authors have proposed a method for the fluorometric determination of carbazole. The fluorescence intensity of carbazole could be selectively measured by the addition of sodium methoxide, potassium iodide and methanol to dimethyl sulfoxide (DMSO) solution of the sample. In this method, the influence of the interfering substances could be greatly decreased because the fluorescence of the interfering substances were quenched by potassium iodide and the fluorescence maximum of carbazole was shifted to longer wavelength by the ionization with sodium methoxide. Five milliliters of a sample solution containing less than about 1μg of carbazole in DMSO was transferred into a 10 ml volumetric flask. Then, 1.5 g of potassium iodide and about 3 ml of DMSO were added. Potassium iodide being dissolved, the solution was cooled to room temperature. Exactly 1 ml of 10 mg/ml solution of sodium methoxide in DMSO containing 20 vol.% of methanol was added. The mixture was diluted to 10 ml with DMSO. Carbazole could be determined by measuring the relative fluorescence intensity at 423 nm with excitation at 392 nm. As the standard, 0.125 μg/ml solution of carbazole prepared under identical conditions was used. As the blank, the solution obtained in the same manner as the sample was used. By this method, as far as 50 ng of carbazole in the presence of (511) μg of interfering substances respectively, such as anthracene, fluoranthene, phenanthrene, acridine, acenaphthene, anthraquinone and pyrene could be determined.