The mass transfer between a single droplet and a surrounding fluid can be described mathematically solving the momentum and mass balances in both phases (conjugate problem). This study of dimensionless parameters shows how the process is influenced by changes in material properties and operating conditions. The influence of the Reynolds number Re on the mass transfer is found to be small and to vanish for creeping flows. A sensitivity to the viscosity ratio mu* exists only in a limited range. The influence of the Peclet number Pe can be approximated for small Pe by considering only the external problem and for high Pe by considering only the internal problem. (c) 2005 Elsevier Ltd. All rights reserved.