In petroleum processing, the intermediate streams contain compounds of the five homologous series-n-paraffins, iso-paraffins, olefins, naphthenes and aromatics (PIONA). It is unwieldy to use all these true compounds in any rigorous simulator to get the actual picture of the plant operations. To attain a quantitative description of the phase equilibrium of such mixtures, a novel shortcut method, which is based on only one key component and the ratio of the adjacent distribution coefficients for homologous series has been developed. At a particular temperature the recursive ratios of the distribution coefficients in a homologous series indicate a fixed value on the main branch. The dependency of relative distribution coefficients on temperature and solvent to feed ratio has been estimated. For all the PIONA families, exponentially distributed feed has been used in the AspenPlus simulator to calculate the distribution coefficients K. The shortcut PIONA LLE simulation program has been trained using the above distribution coefficients to obtain the relative distribution parameter a. For testing PIONA LLE proposition, single-stage liquid-liquid extraction experiments for gamma (continuous) and random (discrete) distributed feeds were done. n-Paraffin and aromatic families were investigated independently. Using this novel approach, shortcut simulation prediction results match well with the experimental data points. It requires less computational time. (C) 2003 Elsevier B.V. All rights reserved.