Desorption of a component from a gas mixture being injected through a submerged nozzle, during the bubble formation stage, is theoretically studied. The solute is assumed to suffer an instantaneous reaction on the liquid side, the reaction plane being on the liquid/gas interface. The volume elements on the gas bubble are assumed to result from a forced surface renewal coupled with a natural surface renewal, both achieved via gas elements with fresh composition. A surface residence time distribution is thus obtained, and desorption rates are calculated from the relevant variables, assuming non-steady state, unidimensional diffusion in a semi-infinite medium as the main mass transfer mechanism. Comparison of the model with experimental data is reported, physical evidence being predicted better than with previous models.