A photoreactor is a chemical reactor with an optical problem to solve, so selection starts with three questions: how much material does it hold, what chemistry must it survive, and how does light reach the reaction. Answer in that order and the remaining choices follow.
Match working volume to the experiment, not the ambition: a half-empty reactor wastes light and changes headspace chemistry, an overfull one starves mixing and gas exchange. Define the required working range, batch flexibility argues for a modest volume with generous headspace; fixed protocols argue for a tight, reproducible fill.
Material decides what the reactor can see through, survive and contain. Borosilicate glass transmits visible and near-UV and resists most aqueous chemistry, the default choice. Quartz extends deep into the UV. Stainless steel handles pressure and aggressive solvents but needs optical windows, and window material then becomes the limiting question.
How light enters defines the reactor type: immersion wells put the source inside the liquid (short path, high flux, thermal load), external windows illuminate from outside (flexible, lower flux), and fiber or side-arm designs deliver light to specific zones. Match the interface to the optical depth your chemistry needs, thin paths for absorbing media, immersion for maximum flux.
Working volume and headspace; pressure and temperature ratings; corrosion compatibility with your real solvent system; transmission of the window at your wavelength; interface geometry and cooling provision; and sampling access. A reactor that passes all six lines fits the experiment instead of fighting it.
Perfectlight's offline photoreactor line covers these configurations; see solutions for application pairings.
