Regulation 1774/2002/EC requires that EU reference laboratories assess the insoluble impurities content in ruminant fat. According to this Regulation, protein-free tallow is defined as fat in which insoluble impurities should not exceed a limit of 0.15%. This article proposes a method that was elaborated, validated and successfully applied on 116 animal fat samples. In the examined contamination range (0.075-0.9%), the values of parameters estimated with this protocol are y=0.989x-0.009, r²=0.999 for linearity, 94.7% for mean recovery, 3.3-8.4% for coefficient of variation, 0.012-0.06% for expanded uncertainty, 0.026 and 0.058% for limit of detection (LOD), and limit of quantification (LOQ), respectively. The present study also assesses the robustness of the method and shows that none of the factors can significantly influence the results of the method.