Evaluation of a C18 hybrid stationary phase using high-temperature chromatography

Alkyl benzenes and aromatic alcohols were used as model analytes in a chromatographic separation on a new type of hybrid C18 stationary phase. The stationary phase was characterized from the point of view of its interaction with the mentioned analytes. The thermodynamic parameters such as Delta H degrees and AS' showed that there are very few differences in the interactions of the alkyl benzenes and aromatic alcohols with the stationary phase in the temperature interval from 150 to 200 degrees C. A temperature study in the range from 30 to 200 degrees C using toluene as an analyte revealed that the van't Hoff plot is non-linear. Differential scanning calorimetry studies on this stationary phase indicated a phase transition at similar to 90 degrees C. Studies on the influence of organic modifier concentrations indicated that the retention of the analytes at 150 degrees C varied linearly with the volume fraction of acetonitrile in the mobile phase. At 150 degrees C the van Deemter plot showed that a minimum was reached for the reduced plate height at similar to 1.6 mL/min which was constant up to 5 mL/min. A 1-month stability study of the column using pure water as a mobile phase, at 200 degrees C indicated that analyte retention factor changed by 10% during this period of time. (c) 2005 Elsevier B.V. All rights reserved.