Hydrodynamic Flow in Capillary-Channel Fiber Columns for Liquid Chromatography
R Stanelle, Lane C. Sander, R K. Marcus
The evaluation of the basic flow characteristics of capillary-channeled polymer (C-CP) fibers proposed for use as the stationary phases for reversed-phase liquid chromatographic separations has been investigated. Stainless steel HPLC columns packed with two types of C-CP fibers (polyester (PET) and polypropylene (PP)) have been studied to determine the basic hydrodynamic characteristics and the roles of fiber packing density and column inner diameter with regards to peak asymmetry, peak width, and run-to-run reproducibility for the unretained probe compound uracil. The C-CP fibers are manufactured with longitudinal grooves (capillary channels) extending the length of the fibers. The diameters of the three C-CP fiber examples were 50 m, 35 m, and 65 m, respectively, with the capillary channel diameters ranging from 6 m to 35 m. Column flow characteristics were studied as a function of fiber packing density ( 0.3 g/cm3 to 0.75 g/cm3) for columns of 4.6 mm inner diameter and at constant packing densities for columns with inner diameters of 1.5 mm, 3.2 mm, 4.6 mm, and 7.7 mm. The van Deemter A-term was evaluated using the probe compound. It was found that increased packing density, while increasing backpressure, does not contribute to peak broadening beyond that due to different volume flow rates at a fixed linear velocity. While column diameter had no influence on the eluting peak widths, there was increased peak asymmetry with increasing column diameter.