Monday, February 16, 2009

Trace chemical analysis of high-purity glass

Summary
Trace-element impurities in high-purity silica (Corning Code 7940 fused silica and J. T. Baker Ultrex silicon dioxide), 96% silica glass (Corning Code 7913), borosilicate glasses (Corning Code 7740 and Owens-Illinois KG-33) and doped optical waveguide glass have been determined by spark-source mass-spectrometry, optical-emission spectrography, neutron-activation analysis, atomic-absorption and plasma emission spectrometry, spectrophotometry, voltammetry and chemical methods. Particular care was taken to prepare samples and carry out analyses in a clean environment with ultrapure reagents. In most cases some 30 elements as well as water were determined by two or more of the techniques indicated. The impurity level for many elements in the high-purity silica and optical waveguide glass is in the ng/g range and in themgrg/g range for the other glasses. Spark-source mass-spectrometry and neutron-activation analyses were carried out not only on samples prepared by a hydrofluoric acid dissolution-evaporation procedure but also on undissolved samples for volatile elements such as B, P, S, As and Hg. Results obtained are discussed with respect to application of the materials as well as to the analytical methods developed


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