Significant retardation of the evaporation rate of levitated aqueous MgSO4 droplets has been found at high concentrations using an electrodynamic balance. Raman spectroscopy was used to study the structural changes, in particular, the formation of contact ion pairs, in supersaturated aqueous MgSO4 droplets at ambient temperatures. As the relative humidity (RH) decreases, single levitated droplets lose water and become supersaturated. A molar water-to-solute ratio as low as 1.54 was obtained, facilitating the study of contaction pairs of unhydrated Mg2+ and SO4 2- ions in MgSO4 solutions. The characteristics of the