Simulation of concentration changes in complex volatile mixtures during evaporation by using gas chromatography

Summary A method is proposed for the simulation of weathering and aging of mixtures of organic components of similar polarity, e.g. gasolines. Semi-empirical equations are derived and tested which correlate the composition of samples after evaporation with the composition of the original material. In this way, changes in composition during partial evaporation of the liquid mixture can be predicted. In the context of forensic investigations this procedure can be helpful for tracing back the composition of the liquid remaining to that of the original unweathered liquid. To perform this simulation, the relative volatilities of the individual components in the mixture have to be known. These are determined by gas chromatographic retention data simultaneously with the concentrations of the volatile components. The paper evaluates the semi-empirical equations employed and discusses the influence of the simplifying assumptions introduced on the accuracy of the simulation.