Novel column oven concept for cold spot large volume sample enrichment in high throughput temperature gradient capillary liquid chromatography

Abstract

AbstractA novel column oven concept with an incorporated cold spot has been tailored for use in capillary liquid chromatography, allowing efficient injection of increased sample volumes by sub‐ambient temperature‐promoted solute enrichment. The column oven system consists of two horizontally connected temperature zones surrounding the packed capillary column. The oven is designed to allow horizontal sliding of the capillary column inside the column oven housing, enabling rapid transportation of the column inlet between the two temperature zones. This design eliminates the time consuming process of re‐cooling the oven after a temperature gradient, which is associated with other column ovens, providing the possibility of high throughput analyses. The cold inlet zone of the oven was operated at sub‐ambient temperatures where elution is suppressed to allow enrichment of large volumes of solutes dissolved in solvents usually associated with high eluting properties. The hot column oven zone allowed temperature‐programmed gradient action, but could also be operated isothermally resulting in a temperature step gradient. The oven was evaluated using the antioxidants Irgafos 168, Irgafos 168‐phosphate, and Irganox 1076 as model compounds using UV‐detection. A 3.5 μm Kromasil C18 0.25 mm ID×20 cm capillary column was used, while the mobile phase and the sample solvent was neat acetonitrile. The flow rate was 5 μL/min. Within‐assay precision and between‐assay precision of peak areas were in the range of 4.3–8.2% relative standard deviation (RSD). The retention time RSD in temperature gradient mode was 2%. The method was linear in the investigated range of 5–100 ng, displaying a correlation coefficient of 0.9995.