The solubility is one of the most important physicochemical characteristics of chemical process. Correlations and predictive techniques are currently being developed to generate solubility data. The empirical correlations are quite successful in correlating the solubility of compounds in the supercritical fluids. In this work, a combined model, based on the optimization theory, was proposed to correlate different compounds in supercritical carbon dioxide. Solubility data from 48 different compounds were collected from literature published from the year of 2008-2013. The global average absolute relative deviations (AARD) of the model results from 1116 experimental data points were reported to investigate the capability of the proposed model and the mostly more accurate empirical models (Ch-Madras, Garlapati-Madras, Adachi-Lu, Jouyban, Sparks, and Bian) in calculations of the solubilities. The results showed that, the proposed Sparks-Jouyban-Bian combined model produced more accurate results (AARD = 4.37%) compared to the six most common empirical models and seven other combined models considered in this study. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.