| Solute descriptors from literature sources were optimized and the revised values used to characterize the retention properties of open-tubular columns for gas chromatography. The average standard deviation for prediction for the revised descriptors on all thirty-nine columns at 0.018 is about three to four-fold better than observed for the original descriptors with an average value of 0.045 for the same columns. The revised solute descriptors were also used to model retention on the carborane-siloxane copolymer stationary phase Stx-500 and a series of five new silarylene-siloxane copolymer stationary phases (ZB-5 ms, DB-5 ms, DB-XLB, DB-17 ms, and DB-35 ms). In all cases the revised solute descriptors provided a better fit to the retention data than the original descriptors establishing their value for column characterization studies. The separation characteristics of the silarylene-siloxane copolymer stationary phases were compared to nominally similar poly(dimethyldiphenylsiloxane) stationary phases using the revised solute descriptors and the solvation parameter model. The ZB-5ms and DB-5ms stationary phases are shown to be selectivity equivalent while for the other stationary phases small but significant differences in selectivity when compared with the nominally similar poly(dimethyldiphenylsiloxanes) are predicted by the solvation parameter model and confirmed by experiment.; To determine solute descriptors for compounds with low water solubility and for compounds that react with water conventional aqueous-based liquid-liquid partitioning systems are not useful. For these applications three totally organic liquid-liquid partition systems (hexane-acetonitrile, n-heptane-methanol, and n-heptane-N,N-dimethylformamide) were characterized using literature and experimentally determined partition coefficients for varied group of neutral compounds. The models developed are capable of estimating further values of the partition coefficient to about 0.1 log units and are applicable to a wide range of compounds. These models are shown to be suitable for estimating partition coefficients for environmentally important compounds that lack experimental values or are unavailable for study and for the determination of solute descriptor values for silicon-containing compounds.; Retention factors determined by reversed-phase liquid chromatography are commonly used for the determination of solute descriptors. It is shown that on high-density alkylsiloxane-bonded (Ascentis C18) silica stationary phases unreliable results are possible for conditions were either steric repulsion or electrostatic interactions contribute to the retention mechanism. Steric repulsion, which depends on the bulkiness of a solute, results in a systemic reduction in retention compared with predicted values for a solute fully inserted in the solvated stationary phase. The bonding density of the stationary phase; the type and composition of the mobile phase; and the size, conformation, type and number of functional groups on the solute are all shown to affect the contribution of steric repulsion to the retention mechanism. Heterocyclic, nitrogen-containing bases are shown to experience additional retention compared with neutral compounds by electrostatic interactions with silanol groups incompletely shielded by the solvated chemically bonded phase.; Solute descriptors were determined for the first time for a large number of industrially important, silicon-containing compounds using the solvation parameter model and the experimental methods described above. Silicon-containing compounds with typical functional groups (alkyl, alkoxy, chloro, phenyl, vinyl, etc.) are generally hydrogen-bond basic but not acidic, electron lone pair repulsive and have low dipolarity/polarizability. Their solvation properties are quite different to organic compounds with a similar carbon skeleton and are closer to perfluorocarbon compounds in their general behavior. The solute descriptors are u... |
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