Progress towards a fiber-optic uranium sensor (detection of uranyl at PPB levels via fluorescence quenching followed by uranyl photooxidation)
- Univ. of South Carolina, Columbia, SC (United States)
Much emphasis has been placed on the determination of nuclear waste products in recent years. We have developed a simple, sensitive and selective method for the determination of uranium as uranyl ion in solution. At low pH uranyl ion will quench the fluorescence of a fluorescein type dye, Fluorexon (Calcein). We attribute this quenching to complex formation between the dye and attribute uranyl ion. In buffered medium, this quenching follows the Stern-Volmer relation with a limit of detection of less than 10 ppb but with a limited linear range. In order to improve selectivity, a second experiment is performed after quenching. Excitation of the sample at a uranyl absorption band (420-450nm) forms the highly oxidative UO{sub 2}{sup 2+} species. This excited state species has an oxidation potential of 2.6V, a photooxidation quantum efficiency of 0.573 and the potential to be regenerated in the reaction cycle. The excited state uranyl presumably photooxidizes the dye causing an increase in fluorescence of the sample solution over time. The degree of fluorescence regeneration and recovery time are proportional to the uranyl ion concentration. Few interfering metal species have been found that exhibit similar behavior. We are attempting to use this system to develop a second-order fiberoptic sensor. The sensor uses a cation-exchange membrane (Nafion) to immobilize the dye and minimize potential interference from dichromate anion.
- OSTI ID:
- 466530
- Report Number(s):
- CONF-951017-; TRN: 96:005999-0062
- Resource Relation:
- Conference: 22. annual conference of the Federation of Analytical Chemistry and Spectroscopy Societies, Cincinnati, OH (United States), 15-20 Oct 1995; Other Information: PBD: 1995; Related Information: Is Part Of FACSS XXII - the 22nd annual conference of the Federation of Analytical Chemistry and Spectroscopy Societies; PB: 285 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Photochemical reduction of the uranyl ion with dialkyl sulfides
Influence of temperature on the fluorescence of uranyl in frozen solutions of phosphoric and sulfuric acids in the presence of quenchers