FPOP platform. A sample syringe, driven by a syringe pump, is connected to silica tubing, where part of the polyimide coating is removed to afford a transparent window. The other end of the capillary is inserted into a collection tube containing reagents to deactivate left-over oxidizing agents. A 248 nm KrF excimer laser is placed such that its beam is perpendicular to the flow system and has lenses to focus the beam on the flow tube. Sample proteins will react with the radicals within the laser window. The flow rate is determined such that between every two solution plugs exists an unexposed portion, termed an “exclusion volume”, that minimizes “double hits” on the protein solution.