DETERMINATION OF SELENIUM IN GLASS BY GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROSCOPY AFTER EXTRACTION WITH DITHIZONE - A COMPARISON WITH X-RAY-FLUORESCENCE AND VAPOR GENERATION ATOMIC-ABSORPTION SPECTROSCOPY

Selenium is used in the glass manufacturing industry as either a decolouring agent or as a colourant, giving pink and brown colourations. In both cases, Se is known to be subject to substantial losses in the melt, while at the same time waste gases emitted from glass tanks are being regulated by stricter standards. Therefore the determination of Se retained in glass and knowledge of the amount emitted in the gases or present in the dust is of great practical relevance. In this paper a HNO3-HClO4-HF digestion procedure is recommended for glass analysis and the hydride generation method applied on the final solution. When this technique could not be applied because of strong suppressive interferences, particularly due to Sb, graphite furnace atomic absorption spectroscopy (GFAAS) has been successfully employed after selective extraction of Se with dithizone in CCl4. The procedure gives results that are in good agreement with other analytical techniques such as the hydride generation AAS, when applicable, or x-ray fluorescence (XRF). In the absence of CRMs for Se trace analysis in glass samples, recovery experiments have been carried out with satisfactory results.