The boron complex with dibenzoylmethane in a suitable medium (e.g. EtOAc) is excited by a small nitrogen laser and emits delayed fluorescence with a lifetime of 2 ms which is much longer than that of fluorescence of uranium; the time resolved fluorometric method can be applied for the determination of boron in uranium. Since the fluorescence of uranium does not interfere with determination of boron, boron need not to be separated from uranium in advance. Thus, the method is very simple and rapid. The limit of determination is 0.02 ng/mL. In a sample of 10 mg U, 0.01 ppm of boron can be determine Boron (0.04-0.5 ppm) was determine in several U3O8 samples by using this method. The results were in agreement with those of obtained from other methods.

Key words: FLUORIMETRIC ANALYSIS, BORON, BORON COMPLEX, BORON COMPLEX, LASER, FLUOROSPECTROPHOTOMETRY, URANIUM OXIDE, FORMYL, TIME RESOLUTION, DIPHENYLMETHANE