Filter paper- and smartphone-based point-of-care tests for rapid and reliable detection of artificial food colorants

Abstract

Herein, a robust instrument-free point-of-care tests (POCTs) strategy was proposed for rapid naked-eye detection of artificial food colorants (AFCs) using filter paper as a sampling and response device. Indicator papers were prepared by one-step polycondensation of silane coupling agents onto glass microfiber filter papers, then colorimetric cards with fine color mappings to AFCs concentration gradients were handily fabricated by AFCs extraction with indicator papers via electrostatic interaction and hydrophobic effect. The lowest concentration for AFCs visual detection was as low as 10−6 M and the whole POCTs process could be finished within 1 min. Furtherly, color information (RGB and gray-scale values) of AFCs-stained indicator papers and colorimetric cards from smartphone APP was used to reconstruct digitized colorimetry and reinforce its validity by mitigating the possible errors from subjective judgement on colors. Finally, such a dual-mode POCTs strategy was experimentally proved to be highly reliable for rapid visual detection of three AFCs (brilliant blue, Allura red, and sunset yellow) in real drinks by contrast with several instrumental methods like spectrophotometry, HPLC and MS. Due to its fine portability, speediness, low cost and user-friendliness, this strategy paves a promising way for AFCs-related food safety control.