In column separations, on the other hand, only the compounds eluted are detected.vA series of different detectors are used for -electrons (low and high energy particles), gamma-rays, and positron emission. Resolution is degraded to some extent by the spatial arrangement of the detector and layer and radioactivity detection is not widely used with HPTLC layers for complex separations. The classic method of detecting labeled compounds by auto radiography, in which the dry layer is placed in contact with photographic (X-ray) film and subsequently developed and scanned, is still in use, but is no longer common practice [56].