Novel applications of elevated temperature high performance liquid chromatography: analyses of triazole fungicides and vitamin E isomers

Abstract

Control of column temperature has become increasingly accepted as a separation parameter in high performance liquid chromatography (HPLC). In this study, high-temperature reversed-phase (RP) HPLC using water-rich and superheated water eluents is evaluated as a new approach for the separation of selected triazole fungicides. Using a polybutadiene-coated zirconia column at temperatures of 100°C to 150°C, clear separations were achieved when 100% purified water was utilized as organic-free eluent. Excellent limits of detection down to pg level were obtained under optimum conditions. Nevertheless, poorer separation efficiency was observed when the triazole fungicides were separated on carbon-clad zirconia column using water-rich eluents. Novel separation of eight vitamin E isomers (a-, ß-, ?-, d- tocopherol, and a-, ß-, ?-, d-tocotrienol) and a-tocopherol acetate on both normalphase (NP) and reversed-phase (RP) HPLC were also examined. All the isomers were successfully separated using NP-HPLC on amino and silica columns. By simply increasing the temperature for silica column, excellent separation efficiencies and shorter analysis times were achieved. Seven vitamin E isomers were successfully separated using RP-HPLC at high temperatures. Both developed separation methods are rapid, showed excellent repeatability, and suitable to be used as a quantitative method in analyzing vitamin E isomers. Pressurized liquid extraction (PLE) along with elevated temperature NP-HPLC is evaluated as a new approach for the determination of ß-carotene and vitamin E isomers in residue oil obtained from palm pressed fiber (PPF). The new developed method demonstrated an outstanding performance with excellent efficiency in terms of total extraction time, total solvent usage, total carotene and vitamin E isomers contents as well as the exceptional method repeatability.