This paper presents numerical simulations of two-phase flow with highdensity ratio, taking into account mass transport of a soluble component and its interfacial mass transfer. Simulations are carried out with an extended version of the highly parallelized code FS3D, which employs an advanced Volume-of-Fluid (VOF) method. For the examination of mass transfer, single bubbles are held in counter- flow to investigate the transient dissolution of a dilute species. In case of small bubbles with laminar wake a rotational symmetric concentration profile occurs, while the local mass concentrations in the wake of larger bubbles show complex patterns of varying concentration as it also has been recently observed experimentally. From the current simulations, a correlation for Sherwood in case of single bubbles results.