Anthracene cell for counting weak-beta-emitting nuclides (sulfur-35) in liquid samples.

In an attempt to simplify the technique for measuring extracellular fluid volume with sulfur-35, a weak beta-emitting radioisotope, an anthracene cell was devised with constant volume and geometry. Anthracene crystals emit a blue flourescent light when exposed to ionizing radiation. Different forms of anthra cene cells have been devised. All consist of packed anthracene crystals in a con tamer exposed to a photomultiplier tube system. ( 1, 2, 3, 4, 5) The liquid con taming the radioactive isotope to be analyzed is intimately mixed with the anthra cene. The problems encountered with the anthracene cells are variations in geometry, distribution of liquid in the cell, and decontamination of the anthracene. This anthracene cell consists of a disc of transparent acrylic resin3 machined to form a shallow unidirectional channel. The channel bed is covered with a thin layer of anthracene crystals which is permanently and securely imbedded on the surface of the acrylic resin. White reflector acrylic resin, with appropriate inlets, is sealed on the surface of the channeled transparent acrylic resin producing a unidirectional liquid-tight tunnel. The cell is fixed with optical silicone paste to a photomultiplier tube which is attached to a high voltage supply and counting