Test substance. The use of a radioactive test substance is required for all stud- ies. Ideally, the purity, radioactive and nonradioactive, is greater than 99 per- cent. The radioactive and nonradio- active test substances shall be chromatographed separately and to- gether to establish purity and identity. If the purity is less than 99 percent or if the chromatograms differ signifi- cantly, EPA should be consulted.
Test substance. The use of radioactive test substance is required for all mate- rials balance and metabolite identifica- tion requirements of the study. Ideally, the purity of both radioactive and non- radioactive test substance should be greater than 99 percent. The radio- active and nonradioactive substances shall be chromatographed separately and together to establish purity and identity. If the purity is less than 99 percent or if the chromatograms differ significantly, EPA should be consulted.
