A separation column for chromatography or a medium for solid phase extraction, which comprises a hollow capillary and a collected body packed in the hollow capillary and serving as a stationary phase, the collected body comprising long fibers having an adsorbing ability selective towards a target solute and arranged in the axial direction of the capillary, and a sample injection system which comprises the foregoing hollow capillary incorporated into a loop of a valve or a passage connecting two valves, the valve(s) being used as an injector for the chromatography. The use of the polymeric long fibers, which have chemical structures specially designed so that they can specifically interact with a target substance (a solute or an analyte) to be analyzed, permits the selective or preferential extraction and/or concentration of the solute.