A precision tracer procedure was developed for the rapid analysis of nonuniformly distributed plutonium in large biological samples. Liver, lung, kidney, lymph node, trachea, gastrointestinal tract, nasal mucosa, pharyngeal mucosa, bone, urine and feces samples from burros, sheep, and dogs (exposed to plutonium aerosols) were assayed for plutonium. The chemical procedure consisted of: equilibration of sample plutonium with 236Pu tracer, wet ashing by refluxing with H2SO4 and a catalyst, extraction of plutonium from bulk salts with cupferron-chloroform, purification with ion-exchange resins, and electro-deposition on platinum. These procedures minimized the requisite volume of acids and avoided the violent exothermic reactions of some wet ashing procedures. Problems associated with dry ashing, such as loss of the radioisotope by entrainment in solid carbon particles and formation of insoluble oxides of plutonium, were avoided. Also, the need for the large ashing furnaces was obviated. The plutonium content was measured by tracer yielding and alpha pulse-height analysis. This method ensured a high degree of accuracy, high sensitivity, and freedom from interference from other alpha emitters. A typical chemical yield was 55 per cent and the counting precision was within 3 per cent. Limits of detection were approximately 0.05 dis/min for a thousand minute count.
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