The presence of clouds in the atmosphere can substantially modify the chemical kinetics and thus the rates of destruction and production of chemical species. Multiphase models are stiffer and rather more difficult to integrate than pure gas models. They contain moreover many physical and microphysical parametres whose values arc often known with poor accuracy. In this paper we focus on two major points. The first one is time integration. We propose the nonautonomous second-order Rosenbrock method in order to solve such heterogenous models. In the second part we focus on the sensitivity analysis of the model outputs with respect to the input parameters using an automatic differentiation tool (ODYSSEE).