RELATIONSHIP BETWEEN GAS-CHROMATOGRAPHIC RETENTION INDEXES AND COMPUTER-CALCULATED PHYSICAL-PROPERTIES OF 4 COMPOUND CLASSES

The Austin Model 1 (AM1) Hamiltonian in MOPAC, a semiempirical molecular orbital program, was used to calculate molecular polarizabilities, ionization potentials, and dipole moments for polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, and dibenzofurans. The relationship between these three physical properties and gas chromatographic retention behavior was investigated. Linear predictive equations using molecular polarizabilities, ionization potentials, and dipole moments squared as independent variables and GC retention indexes as the dependent variable were developed for four classes of compounds. Molecular polarizability was found to be the most important variable in all four models, accounting for more than 90% of the total variance in each case. Depending on the compound class, both ionization potential and the square of the dipole moment were equally effective as the next best predictor. It was found that a standardized combination of these physical properties may be used to develop models for prediction of retention indexes for, at least, four different classes of compounds.