Procedure and apparatus for collecting liquid containing radioactive tracers

A procedure is described whereby a supernatant liquid containing radioactive tracer may be removed from a container, such as a test tube, which also contains animal cells, without any of the cells also being removed. This is useful when cells tagged with radioactive tracer have been killed, thus releasing the tracer to the supernatant liquid, the released activity to be estimated without contribution from undamaged cells. The procedure consists of lowering a suitably shaped absorbent body onto the surface of the liquid from which it is separated by a filter membrane adhering to the lower surface of the membrane, and permeable to the liquid but not to the cells. On all liquid being absorbed the absorbent body is withdrawn for gamma or beta scintillation counting, depending on the transparency of the absorber, while the filter remains in the container. The absorbant body is dispensable. (JIW)