This paper presents a new method for the measurement of mass transfer in isolated water drops. The transport of a component in the water drop can be detected by a change in electrical conductivity. Measurements were performed using a new type of sensor design. In particular the transfer of CO2 from a continuous fluid phase into the water drop was investigated. CO2 leads to an increased conductivity in water because of the carbonic acid equilibrium. Experimental conditions ranged from 298 to 323 K in temperature and from 2.5 up to 30.7 MPa in pressure. The mass transfer coefficients obtained give insight into the transfer process and its physical mechanisms. Increasing temperature and density of the surrounding carbon dioxide lead to faster mass transfer processes. The effects of drop geometry and internal turbulences on the mass transfer velocity are discussed.