Monolithic cartridges including a plurality of nominally aligned polymer fibers (20) can be used as stationary phase materials for liquid chromatography separations. Bundles of fibers (20) are packed together so as to form capillary channels (24) between the fibers (20). Different polymer compositions permit the 'chemical tuning' of the separation process. The fibers (20) can be physically or chemically bonded at spaced locations throughout the cartridge or can be packed together under pressure by use of an encasing wrap to form the capillary channels (24). Use of fibers (20) allows a wide range of liquid flow rates with very low backpressures. Applications in HPLC, cap-LC, prep-scale separations, analytical separations, waste remediation/immobilization, extraction of selected organic molecules/ions from solution, purification of liquid streams (process waste, drinking water, pure solvents), selective extraction of cell matter and bacteria from growth media, and immobilization of cell matter and bacteria are envisioned.