QSPR study of GC retention indices for saturated esters on seven stationary phases based on novel topological indices.

The novel topological indices, polarizability effect index (PEI), odd-even index (OEI) and steric effect index (SV(ij)), previously developed in our team, were extended to predict the gas chromatographic retention indices (RI) of saturated esters on seven stationary phases (SE-30, OV-7, DC-710, OV-25, XE-60, OV-225 and Silar-5CP). The sets of molecular descriptors were derived directly from the structure of the compounds based on graph theory. Multiple linear regression (MLR) models between the RI and the topological indices were established for each stationary phase with a correlation coefficient between 0.9989 and 0.9977 and a leave-one-out cross-validation correlation coefficient between 0.9988 and 0.9975. The average prediction errors over seven phases are within the range of 0.5-0.7%. Statistical analysis showed that the polarizability effect, the molecular size and the branching make dominant contributions to RI of ester compounds, but steric effect also provides separate contribution. The models with topological indices were compared with recently proposed QSRR models of the similar data. It is found that the present indices produce better correlations with Kováts retention indices than the previous topological indices. The significant improvement demonstrates the efficiency of the current study in the quantitative structure retention indices correlations of complex compounds with polar functional group.