The Seebeck effect offers the possibility of rapid analysis of the chemical composition of iron and steels. In this paper, the thermal electromotive forces (TEMF) were experimentally determined in the range of 0.05-0.4%Cu and 0.01-0.1%Sn, respectively, for pure iron and Cr-Ni alloys at different temperatures. The intention is to provide basic data for direct measurement of the contents of the tramp elements Cu and Sn. The thermal EMF measurements were made in an open Tammann furnace under streaming argon gas at rising and falling temperatures. It is demonstrated that reproducible relationships exist between thermal EMF and the content of tramp elements in Fe-based alloys. The contents of Cu and Sn in Fe-based alloys are a linear function of the thermal EMF and temperature.