Even though devices to perform online and inline elemental analysis are widely available, they are generally under-utilised in the mineral processing industry. Instead, information obtained from laboratory analysis of material samples is used for process control, despite of sample analysis being time-consuming, expensive and error prone. Thus, in this paper, we demonstrate that online elemental analysis is a viable alternative to sampling-based material monitoring. To this end, we present the results of field-studies performed in a controlled environment, as well as at a flotation cell of the GTK Mintec mineral processing pilot plant. In both studies, we analyse the copper concentration in a suspension using the FLORIDA XRF device and report relative errors as low as 4% under controlled conditions, and 6% at the processing plant.