Gas chromatography (GC) is very useful and powerful tool in quantitative analysis of practi-cally for any types of objects. The main limitations of GC arise from the necessity of the phase transi-tion from liquid to gas (required in overwhelming majority of cases). This article is dedicated to con-sideration of one of negative analytical consequence of this phase transition known as sample dis-crimination in GC with real life example of its manifestation in interlaboratory study of impurities in glycerol sample.