“…It has been shown (Zhu and Guiochon, 1993; Zhu et al, 1993) that, the shock layer being an asymptotic solution, the corresponding profile, and hence the theoretical value of the SLT, is achieved only when the BC migrates under steady‐state conditions. While this is in principle achieved only after an infinitely long migration distance, experiments show that a rather short column may be sufficient in practice, when the concentration step is high enough and the nonlinear effects are strong (Zhu et al, 1993). In the present experiments the asymptotic solution was reached in all cases since the lowest concentration step was already relatively high (the value of b 1 C always exceeds 1, see Table 1 and Figure 5).…”