A portable front-face fluorescence-sensing platform based on thiourea-Schiff-base for rapid, on-site detection of hazardous mercury contamination in whitening cosmetics.

Developing methods for directly detecting mercury (Hg) in real samples without any pretreatment remains a significant challenge in analytical chemistry. In this study, we developed a portable front-face fluorescence system (PFFFS), a simple, rapid, and highly practical method that requires only the mixing of the sample with the pre-prepared reagent kit for immediate testing, requiring no sample pretreatment, weighing, or digestion, enabling on-site Hg detection in whitening cosmetics. We systematically investigated the effects of pH, reaction time, interfering ion masking agents, and fluorescent probe stabilizers on the measurement of Hg. To mitigate memory effects caused by Hg contamination, single-use disposable reagents and consumables were designed. The correlation between actual Hg content (measured by ICP-MS) and fluorescence intensity obtained from PFFFS was utilized to effectively reduce matrix interference. Under optimal conditions, the method had a detection limit of 6.8 mg/kg and a linear range of 23.2-4429 mg/kg. The proposed method was successfully applied to detect Hg in 216 whitening cosmetics, including various creams, lotions, and essences lotion, with results consistent with those obtained from ICP-MS analyses. Compared with conventional analytical techniques, the PFFFS method offers distinct advantages such as lower cost, shorter detection time (6 min), portability, and suitability for consumer self-testing. This PFFFS approach can serve as an early warning tool for high Hg contamination before routine laboratory testing, protect sensitive laboratory instruments, and enhance consumer safety by enabling rapid on-site screening of potentially hazardous cosmetics. Furthermore, by facilitating timely detection and control of Hg exposure, this method contributes to reducing environmental contamination and associated human health risks.