A mixing-flow reactor for time-resolved reaction measurements distributed in space

Probing short-lived reaction species is challenging owing to the need for both high signal-to-noise ratio, which can require long measurement time, and fast time resolution. Here, a novel in situ sample environment is presented that decouples time resolution from measurement time by distributing reaction time over space for the reaction under flow. In the mixing-flow reactor, precursor solutions are mixed at a specific position along the flow path, where the reaction is initiated. As the reaction mixture flows within a reaction capillary, the reaction time increases with distance from the mixing point. A measurement can be taken at a specific distance from the mixing point for as long as is needed to accumulate good statistics without compromising the time resolution of the measurement. Applications of the mixing-flow reactor for pair distribution function measurements of the initial nuclei formed during the hydrolysis of Al³⁺ at high pH are shown.