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News Archive
Oceanographers Turn to Silver Membrane for Particle Collection
Silver membranes assist in understanding oceanic primary production
and short-term carbon sequestration
Kent, Washington (June 11, 2002) - Sterlitech Corporation reported that silver
membranes are being used by oceanographers to test for climatic changes in
the open ocean. Scientists are using the radioactive marker thorium-234 (234Th)
to better understand the temporal and spatial variability of biological particle
formation and sinking in the ocean. To measure total thorium concentrations,
234Th is scavenged from a relatively small amount of ocean water using manganese
dioxide. The resulting precipitate is filtered onto the silver membrane. Particulate
234Th (and other elements of interest, such as carbon, nitrogen, and silica)
are collected via direct filtration. The radioactivity from the thorium captured
on the silver filter is then non-destructively measured using a beta counter.
"We are pleased that our 1.2 micron filters are being used for this important
research," stated Mark Spatz, President of Sterlitech Corporation. "Silver
membranes have many unique applications and are an especially good collection
media and substrate for analysis."
Silver membranes have four distinct advantages for thorium sampling:
1. No background radiation on silver membranes out of the box. Compared
to a glass fiber filter (GFF) or quartz filter, the silver membrane is free
of 'background' radioactivity.
2. Easily prepared for beta counting. The 25 mm size is
perfect for a standard beta counter.
3. Silver filters are relatively dense and will partially
reflect some of the radioactivity, thus resulting in higher counting
efficiencies.
4. Easy sub-sampling and precise particle collection.
Unlike GFF or quartz filters, silver membranes do not adsorb
dissolved 234Th (or dissolved organic carbon or nitrogen). Furthermore,
particulate samples are stable on the membrane, such that they
can be easily subsampled after 234Th analysis for other elements
of interest, such as carbon, nitrogen, and silica.
For additional information on the use of Sterlitech Corporation membranes for
the process of determining thorium-234 levels in the seawater, please refer
to Benitez-Nelson, C. R., K. O. Buesseler, M. Rutgers van der Loeff, J. E.
Andrews, L. Ball, G. Crossin, and M. A. Charette (2000), "Testing a new
small volume technique for determining 234Th in seawater," Journal
of Radioanalytical and Nuclear Chemistry, 248 (3), 795-799 or directly
to Dr. Claudia Benitez-Nelson, Assistant Professor, Department of Geological
Sciences, University of South Carolina, (www.geol.sc.edu/cbnelson).
Silver metal membranes are available in
micron ratings of 0.2, 0.45, 0.8, 1.2, 3.0, and 5.0 with standard
diameters ranging from 13 mm to 47mm. Sterlitech Corporation is one
of the largest manufacturers of inorganic membranes in the world
and can customize membranes for uses ranging from analytical tests
to high pressure filtration.
For further information on Sterlitech Corporation Silver Metal Membranes please
call (877) 544-4420 or (253) 437-0844, Fax (253) 437-0844, write 22027 70th Avenue
S, Kent, WA 98032-1911 USA, or visit our web site at www.sterlitech.com. |
