Measurement of Cosmogenic 32 P and 33 P Activities in Rainwater and Seawater
1998; American Chemical Society; Volume: 70; Issue: 1 Linguagem: Inglês
10.1021/ac9707500
ISSN1520-6882
AutoresClaudia R. Benitez‐Nelson, Ken O. Buesseler,
Tópico(s)Analytical chemistry methods development
ResumoWe have developed a new method for the collection, purification, and measurement of natural levels of 32P and 33P in rain, marine particulates, and dissolved constituents of seawater. 32P and 33P activities were measured using a recently developed ultra-low-level liquid scintillation counter. Measurement by liquid scintillation counting allows, for the first time, simultaneous measurement of both 32P and 33P. Furthermore, 33P activities are measured with high efficiency (>50%), regardless of the amount of stable phosphorus in the sample. Liquid scintillation also produces energy specific β spectra which has enabled us to identify previously unrecognized β-emitting contaminants in natural samples. In order to remove these contaminants, new methods of purification have been developed which utilize a series of precipitations and anion and cation exchange columns. Rainwater and dissolved seawater samples were extracted from large volumes of rain- and seawater, 5−20 and >5000 L, respectively, using iron-impregnated polypropylene filters. On these filters, it was possible to load between 25 and 30% Fe(OH)3 by weight, over twice that loaded on previously utilized materials. Using our collection, purification, and liquid scintillation counting techniques, it was possible to obtain specific 32P and 33P activities with less than 10% error (2σ) in rainwater and 20% error (2σ) in seawater.
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