XRF may be used for on-line detection of critical elementsTo investigate the feasibility of using X-Ray Fluorescence (XRF) to identify objects containing Indium and other critical material on-line in a waste stream a series of tests were performed on e.g. mobile screen and batteries. Due to the extensive time needed to record the full XRF spectrum of each item and of reference samples of the critical elements to be identified only a small number of samples could be measured. In an on-line situation, however, only a few, narrow, spectral bands needs to be recorded reducing the measurement time to an estimated 10 to 100 milliseconds. Element like In could be detected on mobile phone screens in the low concentration represented by the ITO electrode layer. In the tested batteries Co gave very strong signals.