If reaction slugs are highly coloured, and see-through PTFE/PFA or similar material tubing is used then slug timing can be corroborated by eye. If either of these factors is not the case however, then inline detection is required to 'see' the reaction slug. Several inline detection technologies are commercially available including inline flow NMR, MS, IR or UV. All of these commercial examples however are significantly priced and have a sizeable footprint to accommodate within a fume cupboard that likely already contains a large amount of equipment associated with the flow reactor itself. As a result, multiple groups have reported their efforts to overcome these issues, creating low-cost inline detectors relying on the absorbance of visible spectrum Whilst elegant and likely to generate high quality and sensitive data thanks to the reference measurement being taken, the resultant complex optical setup using a beam-splitter cube and optical fibres of the detector published by Glotz & Kappe makes replication of the literature challenging without sufficient engineering expertise.