Concentrating solutes within aqueous microdrops is one of the processes that have been investigated recently in microfluidic systems. In order to design the process of concentrating solutes within microdrops more precisely, thermodynamic investigation of the process plays an important role. By knowing the equilibrium concentration and size of the drop, the magnitude of the driving force toward equilibrium will be determined which will help researchers to design such processes more accurately. Here, we have investigated the thermodynamic equilibrium of microdrop concentrating processes involving two kinds of solutes: glycerol as a solute with no solubility limit and sodium chloride as a solute with a solubility limit. It is found that the presence of a solubility limit affects the equilibrium of the process significantly in terms of trends in equilibrium concentration and size.