The aim of this diploma thesis was to find a fast and reliable option for vanadium analyses at the FeV 45 production at the Treibacher Industrie AG. The necessity for a quick analysis arised, because in addition to the vanadium oxidation out of a FeNiMoV-alloy, which is part of the process chain, a reaction between phosphorus and oxygen can be observed and as a consequence of this the phosphorus is transferred into the slag. The beginning of the oxidation of phosphorus depends on the one hand on the concentration of phosphorus and on the other hand on the content of vanadium, respectively on the ratio of these two values and therefore a fast analysis had to be found. This should guarantee an optimization of the process time and should also increase the process security in respect of the avoidance of a phosphorus transfer into the vanadiferous slag. First of all the literature was checked concerning the state of development of an online analytic system. Using the PC-program MODDE 7.0, a model was generated that allows the prediction of the vanadium concentration in the alloy during the process. In addition to this, an investigation which concentrated on the selectivity of the vanadium-phosphorus oxidation was carried out. Another chapter of this diploma thesis is occupied with the investigation of the influencing parameters on the dephosphorisation of the remaining FeNiMo-alloy, which represents the last step of the investigated process. Furthermore a determination, concerning the main parameters on the loss of molybdenum during dephosphorisation was made.