Abstract: A flow cell for optical detector includes a flow cell body, a face-seal window, and a pressed illumination window. The flow cell body is formed of an inert material and includes large and small bores, and inlet and outlet passageways in fluid communication with the small bore. The face-seal window is affixed within the large area aperture to form a liquid tight seal, while the pressed illumination window is press-set into the small bore. The pressed illumination window is spaced away from the face-seal window to form a sample chamber having a pathlength distance ?. The face-seal window and the pressed window provide an optical path through the sample chamber. Preferably, the flow cell body is formed of PEEK. Methods of forming and using the flow cell are also disclosed.