naphthoquinones and n-propylbenzene

Low-temperature high-performance liquid chromatography, in which a loop injector, column, and detection cell were refrigerated at -35ºC, using liquid carbon dioxide as the mobile phase was developed. Small organic compounds (polyaromatic hydrocarbons, alkylbenzenes, and quinones) were separated by low-temperature high-performance liquid chromatography at temperatures from -35 to -5ºC. The combination of liquid carbon dioxide mobile phase with an octadecyl-silica (C18 ) column provided reversed phase mode separation, and a bare silica-gel column resulted in normal phase mode separation. In both the cases, nonlinear behavior at approximately -15ºC was found in the relationship between the temperature and the retention factors of the analytes (van't Hoff plots). In contrast to general trends in high-performance liquid chromatography, the decrease in temperature enhanced the separation efficiency of both the columns.

Topics: Acetonitriles; Anthracenes; Anthraquinones; Benzene Derivatives; Calorimetry, Differential Scanning; Carbon Dioxide; Chromatography, High Pressure Liquid; Cold Temperature; Hexanes; Naphthalenes; Naphthoquinones; Organic Chemicals; Pyrenes; Quinones; Silicon Dioxide