Determination of natural 32P and 33P in rainwater, marine particles and plankton by low-level beta counting
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Methods were developed for determining the natural levels of P-32 and P-33 in samples of rainwater, marine particulate matter and plankton. Preconcentration from rainwater consists of the extraction of radiophosphorus on alumina. Filtration of large volumes of seawater is required to obtain sufficient quantities of suspended particulate matter. The radiochemical scheme, which consists of a series of precipitations and a column separation, results in a pure source containing the two beta emitters. The activities of P-32 and P-33 in the source are determined separately by an external absorber method on low-level beta counters. The yields are monitored by the addition of stable phosphate in rainwater samples and by the natural levels of stable phosphate in marine particulate matter and plankton. The methods allow the specific activities and the activity ratio to be determined with a 10% precision.