Molecular structural vector description and retention index of polycyclic aromatic hydrocarbons

A molecular electronegativity–distance vector (MEDV) has been proposed to describe the structure of polycyclic aromatic hydrocarbons (PAHs) and relate to their retention indices (RI) for programmed temperature SE-52 capillary-column gas chromatography. The 209 PAHs investigated contain not only one or two heteroatoms such as nitrogen, oxygen and sulfur but also one, two or more conjugated rings. Applying multiple linear regression (MLR) in combination with the cross-validation (CV) technique, a four-parameter quantitative structure–retention relationship (QSRR) of 209 PAHs is developed with the correlation coefficient (R) of 0.9812 and the root mean square error (RMS) of 15.533 between the estimated and experimental retention indices (RI). It was found that the errors for oxygen-containing PAHs are often positive and for sulfur-containing PAHs, negative. Thus, MEDV is modified by lengthening the CO or CO bond and by shortening the CS bond. Leaving out several outliers, a better QSRR is described with R=0.9936 and RMS=9.212 for 172 PAHs.