Colorimetry Combined with Inner Filter Effect-Based Fluorometry: A Versatile and Robust Strategy for Multimode Visualization of Food Dyes

Abstract

Herein, a strategy combining colorimetry and inner filter effect (IFE)-based fluorometry was developed for multimode visualization of food dyes (FDs) using CdTe quantum-dots-doped fluorescent indicator papers as a sample-to-answer device. Colorimetry was straightforwardly achieved by FDs extraction through electrostatic interaction and hydrophobic effect while fluorometry was implemented by IFE-induced fluorescence quenching. RGB/gray-scale values of colorimetry and fluorometry were furtherly picked by a smartphone application and applied to reconstruct color information-based digital image analysis for both direct alignments and linear regression analysis. The apparent color and fluorescence of FDs-bound indicator papers, together with their digitized color information, showed a good mapping to FDs concentrations in the range of 0–0.5 mg/mL for Sunset Yellow, 0–0.2 mg/mL for Allura Red, and 0–0.08 mg/mL for Brilliant Blue. As a proof of concept, the dosages of these FDs in real beverages and simulated dye effluents were deduced and cross-validated by different visualization modes, and finally double-checked by instrumental techniques such as spectrometric methods, high-performance liquid chromatography (HPLC), and mass spectroscopy (MS). The above findings concluded that (i) IFE mechanism is generally applicable to build fluorometric systems and (ii) cross validation of different visualization modes can markedly improve detection accuracy, which may provide references for design and fabrication of novel “lab-on-paper” devices for visualization applications with high reliability.

Theoretical predictions and experimental verifications of SERS detection in colorants

“…For instance, colorimetry, uorometry, combination of colorimetry and uorometry, surface-enhanced Raman spectroscopy (SERS), and their derivatives combining with lter paper and/or smartphone for visual readout have made great progress in enhancing portability and practicality. [17][18][19][20][21][22][23][24] These techniques can be very useful and promising for food colorant detection due to their good sensitivity, repeatability and stability.…”

Implantable photonic neural probes with 3D-printed microfluidics and applications to uncaging

“…The performance of the 3D-printed microfluidic channel on Probe 1 was characterized (Section 4.1.1). A 4 mM Allura red dye solution (A0943, TCI Deutschland GmbH, Eschborn, Germany) was prepared to investigate the diffusion profile at the channel outlet (Wang et al, 2022 ). The packaged neural probe was fixed to a translation stage for insertion into a 1% w/v agarose gel block.…”