Radioactive nuclides emitting β+-radiation are used for labeling in PET diagnostic.Before the radioactive labeled agent can be used, the radiochem. purity has to be determined by means of two sep. radio-chromatog. methods.For HPLC, TLC, GC and CE special radioactivity detectors sensitive for β+-radiation are required, which fulfil the regulations of various international and national authorities.All conventional chromatog. detectors in applications of HPLC, TLC, GC and CE like UV-absorption, fluorescence, reflective index, conductivity, amperometry etc. have an analog signal output 0-1 V. Therefore all signal recording and peak integration systems for chromatog. have analog inputs of 0-1 V.