Study of Quantitative Structure–Retention Relationship (QSRR) of Gas Chromatography for Polychlorinated Dibenzothiophenes on Non-polar Columns

Optimized calculation of 135 Polychlorinated Dibenzothiophenes (PCDTs) was carried out at B3LYP/6-31G* level with Gaussian 98 program. The structural and thermodynamic parameters identified with the Theoretical Linear Solvation Energy Relationship (TLSER) model were employed as theoretical descriptors in the Quantitative Structure–Retention Relationship (QSRR) models derived to predict Retention Indices (RI) of PCDTs. Two QSRR models developed for RI of PCDTs contain only one variable: the mean molecular polarizability (α) and entropy (S⊖), respectively. The best fitted equation for the correlation between RI and α of 25 PCDTs with experimental data was RI=−126.52(±2.86)+0.97(±0.01)α with R2 as 0.9942, SD as 2.22, suggesting high accuracy of the RI predicting model. The correlation between RI and S⊖ is strong, and the equation was RI=−184.17 (±3.09)+0.48(±0.01)S⊖ with R2 as 0.9961, SD as 1.81. Furthermore, using position of Cl substitution (NPCS) method, QSRR model of PCDTs was obtained: RI=6.23(±0.75)+13.36(±0.19)N with R2 as 0.9953, SD as 1.99. Method validation also showed that the three models of this study exhibit optimum stability. Finally, RI values of 110 PCDT congeners without experimental value were also predicted with the three models, respectively.