Multiplexed colorimetry collaborated with smartphone-based image analysis for simultaneous and fast visualization of dyes in both environmental and food samples

In this work, a multiplexed colorimetric strategy was initiated for simultaneous and fast visualization of dyes using low-cost and easy-to-prepare indicator papers as sorbents. Response surface methodology (RSM) was employed to model statistically and optimize the process variables for dyes extraction and colorimetric assays. Multiplexed colorimetry was realized by virtue of synchronous color alignments from different dimensions of multiple dyes co-stained colorimetric cards under RSM-optimized conditions, and smartphone-based image analysis was subsequently performed from different modes to double-check the credibility of colorimetric assays. As concept-to-proof trials, simultaneous visualization of dyes in both beverages and simulated dye effluents was experimentally proved with results highly matched to HPLC or spiked amounts at RSM-predicted staining time as short as 50 s ~3 min, giving LODs as low as 0.97 ± 0.22/0.18 ± 0.08 μg/mL (tartrazine/brilliant blue) for multiplexed colorimetry, which much lower than those obtained by single colorimetry. Since this is the first case to propose such a RSM-guided multiplexed colorimetric concept, it will provide a reference for engineering of other all-in-one devices which can realize synchronous visualization applications within limited experimental steps. Environmental pollution, especially water pollution, caused by coexistence of different dyes is increasingly serious, thus it is of great significance to develop advanced techniques for simultaneous detection of dyes. Unfortunately, existing methods for multiple dyes determination are governed by bulky instruments, which are high-cost, skilled personnel relied, and not suitable for rapid on-site detection. Multiplexed colorimetry is a feasible pathway to achieve this goal, but it is still very challenging. Herein, a multiplexed colorimetric strategy with fine practicability for visualization of different dyes was initiated and double-checked by smartphone-based image analysis as well as instrumental techniques like spectrometry and HPLC.