Colorimetry Detects Beryllium
Beryllium, three times lighter than aluminum and six times stronger than steel, is an attractive choice for many applications, including as a mirror substrate. But the inhalation of beryllium powder can cause a potentially fatal disorder of the immune system that is currently impossible to cure. A new test may make handling the substance safer.
Researchers at Los Alamos National Laboratory in Los Alamos, N.M., are interested in beryllium because its low atomic number makes it a good moderator for the neutrons emitted during radioactive decay. Laboratory scientists Tammy Taylor and Nancy Sauer wanted a method to quickly, safely and accurately evaluate beryllium contamination on surfaces. They came up with a visually evaluated colorimetric swipe test.
The researchers pretreat cellulose filters by soaking them in a solution of chrome azurol and then in EDTA. When dry, the filters can be used to wipe a 30.5 x 30.5-cm area that has been lightly sprayed with HNO3 to loosen any beryllium dust on the surface. A test filter is then saturated with a pH 10 solution of ammonia and ammonium chloride to detect the dust.
The beryllium picked up by the surface swab creates a chemical complex with the chrome azurol, and EDTA binds any elements that would compete with this attachment. In the pH 10 environment, the chrome azurol-beryllium complexes turn from reddish-orange to blue, with the strength of the color change proportional to the level of contamination. The user, therefore, can detect the presence of beryllium simply by looking for blue.
The swipe technique displays 100 percent reproducibility of a detectable blue tint at a beryllium concentration of 0.19 µg/100 cm2, slightly less than the Occupational Safety and Health Administration's prescribed safety limit. OSHA has a more sensitive test to detect and quantify beryllium contamination that must be performed whenever a manufacturing operation may create the dust, but it takes approximately three days from sampling to result. Taylor emphasized that the new technique is not designed to replace the mandated tests, but to provide immediate feedback concerning the safety of a work space.
Public release planned
Although the new test has been performed in machine shop environments, Taylor is working to extend its application, such as to the monitoring of the soils at firing sites and of test vessels in the field. "We're performing swipes in the field and doing complete metal analyses so we can load the colorimetric swipes up with typical metal concentrations for these environments," she said.
The test is being patented and is available for use by US Department of Energy personnel. Public release is planned where the test could reduce worker exposure to beryllium while maintaining productivity.
That immediate practical benefit is an exciting prospect for Taylor. "The technique has the potential to help so many people who work with beryllium in laboratories or machine shops keep their work environments safe," she said. "The swipe method is extremely simple to perform, and results can be analyzed in a short period of time."
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