Nowadays,microreactors are becoming more popular in the biocatalytic field to speed up reactions and improve the controllability,e.g.Roberts et al.[1] used a microreactor to generate and identify the unstable products of a reaction catalysed by flavin-dependent amino oxidase(PAO).In order to retrieve these unstable and thus short-lived products efficiently from a microreactor,an extraction step should happen at the location where the concentration of the unstable product is high,which means after the formation of the product,but before the decomposition of the product [2].