The molecular simulation of heterogeneous systems cannot be performed routinely. The results of such systems depend on the truncation procedures, size effects, long range corrections to the thermodynamic properties and on the way of calculating the Coulombic interactions. We propose here to illustrate the impact of the truncation procedures on the mechanical equilibrium of the liquid-vapor interface of alkanes. The importance of the long range corrections to the surface tension is established in alkanes, water, carbon dioxide and hydrogen sulfide liquid-vapor interfaces. The calculation of the electrostatic interactions in a slab geometry using a two-dimensional method and the standard three-dimensional Ewald summation technique is also reported.