Combined effects of mobile phase composition and temperature on the retention of homologous and polar test compounds on polydentate C8 column.
Combined effects of temperature and mobile phase on the reversed phase chromatographic behavior of alkylbenzenes and simple substituted benzenes were investigated on a Blaze C8 polydentate silica-based column, showing improved resistance against hydrolytic breakdown at temperatures higher than 60 degrees C, in comparison to silica-based stationary phases with single attachment sites. For better insight into the retention mechanism on polydentate columns, we determined the enthalpy and entropy of the transfer of the test compounds from the mobile to the stationary phase. The enthalpic contribution dominated the retention at 80% or lower concentrations of methanol in the mobile phase. Entropic effects are more significant in 90% methanol and in acetonitrile-water mobile phases. Anomalies in the effects of mobile phase on the enthalpy of retention of benzene, methylbenzene and polar benzene derivatives were observed, in comparison to regular change in enthalpy and entropy of adsorption with changing concentration of organic solvent and the alkyl length for higher alkylbenzenes. The temperature and the mobile phase effects on the retention are practically independent of each other and--to first approximation--can be described by a simple model equation, which can be used for optimization of separation conditions.
Jandera
Pavel
P
Department of Analytical Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, CZ-53210 Pardubice, Czech Republic. pavel.jandera@upce.cz
Krupczyńska
Katarzyna
K
Vynuchalová
Katerina
K
Buszewski
Bogusław
B
D000097:Acetonitriles / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D057927:Hydrophobic and Hydrophilic Interactions; D016014:Linear Models; D000432:Methanol / Q000737:chemistry; D008956:Models, Chemical; D015203:Reproducibility of Results; D013696:Temperature; D013816:Thermodynamics
D000097:Acetonitriles; D001555:Benzene Derivatives; D000432:Methanol; C032159:acetonitrile