A system for analyzing a fluid includes or uses a movable flow cell assembly being disposed in an analysis location on a wall of an analysis instrument and being configured to be retained by a locking assembly on a first surface of the wall. The system includes a probe head assembly located on an opposed second surface of the wall, the probe head assembly to direct an X-ray source to analyze the fluid in a static state in the movable flow cell assembly or in a flow mode through the movable flow cell assembly. The movable flow cell assembly and the probe head assembly are in electro-magnetic communication for elemental analysis of the fluid using the X-ray source when the movable flow cell assembly is retained by the locking assembly on the first surface of the wall.