The Separation by Means of the Zone-melting Technique and the Spectrofluorometric Determination of Trace Amounts of Anthracene in Phenanthrene

Abstract

Abstract Since ordinarily available phenanthrene contains interfering impurities, such as phenanthrenequinone and fluoranthene, it is difficult to determine anthracene by spectrofluorimetry directly. Trace amounts of anthracene in phenanthrene can, however, be selectively separated from the interfering impurities by means of the zone-melting technique, for the distribution coefficient of anthracene in phenanthrene is greater than unity. The anthracene thus separated is spectrofluorometrically measured using xylene as the solvent. The determination limit of anthracene is 0.05 ppm. In a glass tube with an i.d. of 4 mm, 4.0 g of the sample was charged to a length of about 27 cm, and then the zone-pass was repeated 20 times. The molten zones were set to travel at a speed of 100 mm/h under constant stirring. Exactly 2.5 g of the zone-molten sample was cut out and dissolved in 50 ml of xylene. The fluorescence intensity of the solution was measured at 403 nm with excitation at 378 nm. The recovery of anthracene was 95%, with a coefficient of variation of 0.6%. The incompleteness of the recovery was corrected for.