Identification of Fluorescent Brighteners as Another Emerging Class of Abundant, Ubiquitous Pollutants in the Indoor Environment

Fluorescent brighteners (FBs) are extensively used as important chemical additives in multiple industrial fields worldwide. The history of the use of global FBs spans over 60 years, but knowledge on their environmental occurrence and risks remains largely unknown. Here, we screened indoor dust and hand wipes from South China for a broad suite of 17 emerging FBs using a new comprehensive analytical method. All 17 FBs were detected in the indoor environment for the first time, most of them having been rarely investigated or never reported in prior environmental studies. Ionic FBs were found to be more abundant than nonionic ones. The median total concentrations of the 17 detectable FBs reached 11,000 ng/g in indoor dust and 2640 ng/m² in hand wipes, comparable to or higher than those of well-known indoor pollutants. Human exposure assessment indicated that hand-to-mouth contact is a significant pathway for exposure to FBs, with a comparable contribution to that of dust ingestion. Most of the newly identified FBs are predicted to have persistent, bioaccumulative, or toxic properties. Our work demonstrates that FBs are another class of highly abundant, hazardous, and ubiquitous indoor pollutants that have been overlooked for decades and points to an emerging concern.

Quaternary ammonium salt ion pair reagent sensitizing for determination of fluorescence whitening agent 85 in paper food packaging

Fluorescent whitening agents (FWAs) are added to food packaging during manufacture to improve the whiteness and brightness. It is of great significance to develop a fast and sensitive FWAs detection method because their potential hazards to human health. Herein, we found that the quaternary ammonium salt ion pair reagents could enhance the fluorescence of FWAs, and then developed a fluorescent determination method for FWA 85 in paper food packaging. Under the optimized conditions, the linear range for the determination of FWA 85 was 5-200 ng/mL (R² = 0.9996). The limit of detection was 1.20 ng/mL (S/N = 3) and the limit of quantitation was 3.99 ng/mL. The analytical feasibility was investigated further via determination of FWA 85 in paper food packing, which shows the recoveries were varied from 83.84% to 115.29% with RSDs from 1.64% to 7.22%. The method provides a new quaternary ammonium salt ion pair reagent sensitization for the detection of FWAs in paper food packaging.

Substituent effects on the ultraviolet absorption properties of stilbene compounds-Models for molecular cores of absorbents

The effects of substituent X and Y on ultraviolet (UV) absorption properties of stilbene compounds XPhCHCHPhY (XSBY) were studied both experimentally and computationally from the viewpoint of UV maximum absorption wavelength (λ_max) and the corresponding energy (υ_max). In the studies, the contribution of substituents on υ_max shift was explored. The results show that with increase of electron withdrawing or electron donating ability of X or Y, there is an enhanced electron delocalization of XSBY that leads to bathochromic shift. Computational analyses based on density functional theory were conducted to elucidate the phenomena. It is disclosed that the υ_max values are significantly affected by the excited state, though the electronic effect of ground state cannot be ignored. Finally, on the basis of the respective influences of X and Y, a quantitative model, which was proved reliable by the leave-one-out method, was developed to scale the effects of terminal substituents on υ_max. According to the model, the effects of substituents X or Y exhibit almost the same action on υ_max owing to the symmetric skeleton of the XSBY compounds. The findings provide deep insight into the effects of terminal substituents on UV absorption properties of stilbene compounds, and the derived model enables practical expression of the relationship between substituents and UV absorption.

Molecularly imprinted covalent organic polymers for the selective extraction of benzoxazole fluorescent whitening agents from food samples

Molecularly imprinted covalent organic polymers were constructed by an imine-linking reaction between 1,3,5-triformylphloroglucinol and 2,6-diaminopyridine and used for the selective solid-phase extraction of benzoxazole fluorescent whitening agents from food samples. Binding experiments showed that imprinting sites on molecularly imprinted polymers had higher selectivity for targets compared with those of the corresponding non-imprinted polymers. Parameters affecting the solid-phase extraction procedure were examined. Under optimal conditions, actual samples were treated and the eluent was analyzed with high-performance liquid chromatography with diode-array detection. The results showed that the established method has a wide linearity, satisfactory detection limits and quantification limits, and acceptable recoveries. Thus, this developed method possesses the practical potential for the selective determination of benzoxazole fluorescent whitening agents in complex food samples.

Investigating the interaction mechanism of fluorescent whitening agents to human serum albumin using saturation transfer difference-NMR, multi-spectroscopy, and docking studies

Characterization of the interaction between two fluorescent whitening agents and human serum albumin: ¹H STD-NMR, multi-spectroscopy, and docking studies.