A low pressure liquid chromatographic cartridge is provided having a tubular polymer container adapted to receive a chromatographic packing material. The container has an outlet port located at a downstream end of the container and container threads formed on an upstream end of the container. A polymer cap having cap threads located on the cap threadingly engage the container threads. An inlet port is located on an upstream end of the cap. A flange depends from the cap and mates with the lip of the container to form a fluid tight seal between the polymer cap and container suitable for use in low pressure liquid chromatography. A locking tab on a skirt of the cap engages a recess on the container when the seal engages the cap and container to lock the cap in position relative to the container. Alternatively, continuous screw threads on the cap and container may hold the parts together.