Deep-eutectic solvent coated paper: A reusable multi-purpose device for rapid visualization, adulteration identification, efficient removal and recycling of dyes in both food and environmental samples

Herein, a multi-use strategy was initiated for visual point-of-care tests, adulteration identification, removal and recycling of dyes in both environmental and food samples using hydrophobic deep-eutectic solvent (HDES)-coated paper as an all-in-one device. HDES, which composed by decylic acid and tetraoctylammonium bromide, was prepared as a sorbent for dyes, then paper devices were facilely fabricated by coating HDES onto printing papers. Due to the coexistence of carbon chains, carboxyl and quaternary ammonium groups, HDES-mediated dyes extraction was of fine versatility through electrostatic interaction and hydrophobic effect, by which the recycling rate of dyes reached 96.5 % at only 5 min of extraction time. Colorimetry of dyes in simulated dye effluents and drinks could be ended as fast as 10 s with LODs at 10 −3 mg/mL level, and the colorimetric results were highly agreed with those generated by instrumental techniques and smartphone-based image analysis. Identifications of fruit/vegetable juices and chili oil adulterated with the same-color artificial dyes were also realized in a single paper strip, giving an identification capacity low as to 1.5 × 10 −3 mg/mL. The success of these cases enlightens a new direction for HDES-based multi-purpose application.