What can be detected from a single void urine bioassay?

• A. Tritium
• B. Uranium
• C. Gamma Emitters
• D. Plutonium

Answer: (A)

A single void urine bioassay is most effective for detecting radionuclides that are rapidly cleared into urine after exposure. Tritium fits this pattern: after intake, it is quickly excreted in urine, and a urine sample collected in a single void can be measured with liquid scintillation counting to reveal its activity. In contrast, uranium and plutonium tend to be retained in body tissues and are excreted slowly or irregularly, often requiring a 24-hour collection and chemical concentration to achieve reliable detection. Gamma emitters can sometimes be detected, but their excretion in urine is not as consistently rapid or predictable for a single-void sample, and sensitivity can be lower depending on the nuclide and form. So, the ability to detect from a single void urine bioassay is best exemplified by tritium.