Applications of the solvation parameter model in chromatography and for estimating chemical properties

An iteration procedure is used to optimize the solute descriptors for 93 compounds suitable for characterizing the retention properties of open-tubular columns for gas chromatography in the intermediate temperature range of 150-250°C. These solute descriptors are used to calculate the system constants of the solvation parameter model for thirteen open-tubular columns at increments of 20°C from 160 to 240°C. The optimized descriptor values afford a two- to three-fold improvement in the fit to the retention model compared with literature values as determined by the standard deviation of the difference between the model predicted and experimental retention factors (log k). Combining literature values for the system constants at lower temperatures (60-140°C) with those obtained here allowed system maps to be constructed for the nine columns over the full temperature range of 60-240°C.;Differences in the system constants of the solvation parameter model and retention factor correlation plots for varied solutes were used to study the retention mechanism on XBridge C8, XBridge Phenyl , XTerra C18, XTerra Phenyl , XBridge C18, XBridge Shield RP18 and Sunfire C18stationary phases with acetonitrile-water and methanol-water mobile phases containing from 10 to 70% (v/v) organic solvent. The XBridge stationary phases are all quite similar in their retention properties with larger difference in absolute retention explained by differences in cohesion and the phase ratio, mainly, and smaller changes in relative retention (selectivity) by the differences in individual system constants and their variation with mobile phase type and composition. None of the XBridge stationary phases are selectivity equivalent but XBridge C18 and XBridge Shield RP 18 have similar separation properties, likewise so do XBridge C 8 and XBridge Phenyl, while the differences between the two groups of two stationary phases is greater than the difference within either group. The limited range of changes in selectivity is demonstrated by the high coefficient of determination (> 0.98) for plots of the retention factors for varied compounds on the different XBridge phases with the same mobile phase composition.;The solvation parameter model was used to characterize interactions responsible for the sorption of varied organic compounds by diesel soot and atmospheric aerosols at 15°C and 50% relative humidity. Individual models are obtained for eight aerosol samples characterized as urban, suburban, rural and coastal. Combining the individual aerosol models resulted in a general aerosol model with only a minor loss of modeling power for alkanecarboxylic acids and low-molecular weight alcohols compared with the individual models. A second group of compounds identified as weak nitrogen-containing bases were consistent outliers to all models most likely due to participation in ion-exchange interactions not considered by the models. The diesel soot and atmospheric aerosols exhibit similar characteristics with respect to their sorption interactions although differences in relative magnitude allow the two particle types to be easily distinguished. Sorption interactions are favored by strong dispersion interactions for both particle types. Of note is the strong hydrogen-bond basicity and relatively weak hydrogen-bond acidity of these materials. The particles are quite dipolar/polarizable and slightly electron lone pair repulsive. The sorption properties of the atmospheric aerosols are influenced by the relative humidity, in particular, the aerosols become significantly more hydrogen-bond acidic at high relative humidity most likely due to incorporation of increasing amounts of condensed or film water in the aerosol phase. Dividing the data into training and test sets suggests that the proposed models are capable of estimating distribution constants (log K) to about 0.20 log units for diesel soot (n = 84) and 0.14 log units for the general atmospheric aerosol model (n = 385) where n indicates the number of compounds included in the model.;Measurement of retention factors by gas chromatography on up to 15 complementary stationary phases at up to 5 temperatures in the range 60-240°C for each stationary phase and liquid-liquid partition coefficients in three biphasic organic solvent systems (n-hexane-acetonitrile, n-heptane-N,N-dimethylformamide, and n-heptane-2,2,2-trifluoroethanol) were used to estimate solute descriptors for 28 semivolatile linear and cyclic organosilicon compounds for use in the solvation parameter model. Regression analysis for oligomeric compounds allowed estimation of the descriptor values for the dimethylsiloxane, diethylsiloxane, methylvinylsiloxane, and methylhydrosiloxane monomer groups. (Abstract shortened by UMI.)...