In this study, the interaction ways between n-butyl amine and SBA-15 molecular sieve were evaluated when the TPD technique is carried out to determine the total acidity of that solid. Experimental results (FTIR, TG/DTG, total acid, and catalytic activity) and theoretical calculations demonstrated that the n-butyl amine, used as probe molecule to total acidity determined by TPD, can act as acid or base depending on the nature and force of the active sites on SBA-15.