LAUSR

The design and construction of a low-cost and compact USB photometer based on open source hardware and software is described. The device, featuring a 1 ms sample acquisition time, utilizes a single interchangeable light emitting diode (LED) as a light source in combination with photodiode detectors and a Texas Instruments LaunchPad as the main control unit. An appropriately constructed flow cell can be connected to a flow reactor made out of transparent polymeric material such as perfluoroalkoxy (PFA) tubing. The flow cell can be moved to different positions of the tube in order to take measurements at different residence times without having to disassemble the photometer or the flow reactor system. The bespoke photometer was used to determine the residence time distribution (RTD) of various microreactors/micromixers, as well as for measuring the reaction rate constant for the base-induced hydrolysis of p-nitrophenol acetate in a biphasic segmented flow system. Owing to the 1 ms sample acquisition time of the novel device the lengths of individual segments can be measured in real time.