Using the method of molecular-statistical calculations for predicting chromatographic characteristics of aromatic acids, aldehydes and phenols on porous graphite carbon

Abstract

The efficiency of using the Henry's constant of adsorption (calculated without taking into account the influence of the solvent) as a molecular descriptor for predicting the retention time on porous graphitized carbon (PGC) is shown. Influence of different factors on adsorption on PGC is investigated. Absence of influence of hydrophobic interactions is demonstrated. Different aromatic are considered.

For a number of aromatic compounds of various classes (substituted derivatives of benzaldehyde, benzoic acid, phenol, cinnamic acid, coumarin, furfural) results of Monte-Carlo molecular modelling of adsorption on a homogeneous surface without influence of solvent were compared with experimental data on the chromatographic retention of these substances on porous graphitized carbon under liquid chromatography conditions. Molecular-statistical method was involved in the calculation. The experimental data used in the work were obtained for the following composition of the mobile phase: the acetonitrile: water ratio is 3: 1, pH = 4.2.

There is a significant correlation between the results of the molecular-statistical calculation (for a homogeneous surface without taking into account the solvent) and the experimental retention coefficients. However, this correlation is not sufficient for reliable prediction of retention times.

It was shown that it is promising to use empirical formulas that take into account various factors that affect on adsorption. The empirical formulas for the calculation of the retention coefficient were chosen. The absence of a significant effect of hydrophobic interactions is shown. It was shown that the Henry's constant of adsorption, calculated without taking into account the solvent, should be used as a molecular descriptor in the empirical formulas