A comparison between chemical and photochemical vapor generation techniques for mercury determination using univariate and multivariate optimization

Fluorescent and Colorimetric Dual-Mode Strategy Based on Rhodamine 6G Hydrazide for Qualitative and Quantitative Detection of Hg2+ in Seafoods

In this study, a rapid fluorescent and colorimetric dual-mode detection strategy for Hg²⁺ in seafoods was developed based on the cyclic binding of the organic fluorescent dye rhodamine 6G hydrazide (R6GH) to Hg²⁺. The luminescence properties of the fluorescent R6GH probe in different systems were investigated in detail. Based on the UV and fluorescence spectra, it was determined that the R6GH has good fluorescence intensity in acetonitrile and good selective recognition of Hg²⁺. Under optimal conditions, the R6GH fluorescent probe showed a good linear response to Hg²⁺ (R² = 0.9888) in the range of 0-5 μM with a low detection limit of 2.5 × 10^-2 μM (S/N = 3). A paper-based sensing strategy based on fluorescence and colorimetric analysis was developed for the visualization and semiquantitative analysis of Hg²⁺ in seafoods. The LAB values of the paper-based sensor impregnated with the R6GH probe solution showed good linearity (R² = 0.9875) with Hg²⁺ concentration in the range of 0-50 μM, which means that the sensing paper can be combined with smart devices to provide reliable and efficient Hg²⁺ detection.

Photoactive Titanium Dioxide Films with Embedded Gold Nanoparticles for Quantitative Determination of Mercury Traces in Humic Matter-Containing Freshwaters

Mercury detection in humic matter-containing natural waters is often associated with environmental harmful substances for sample preparation. Herein we report an approach based on photoactive titanium dioxide films with embedded gold nanoparticles (AuNP@TiO₂ dipstick) for chemical-free sample preparation and mercury preconcentration. For this purpose, AuNPs are immobilized onto a silicon wafer and further covered with a thin photoactive titanium dioxide layer. The AuNPs allow the preconcentration of Hg traces via amalgamation, while TiO₂ acts as a protective layer and, at the same time, as a photocatalyst for UV-C radiation-based sample pretreatment. Humic matter, often present in natural waters, forms stabile complexes with Hg and so hinders its preconcentration prior to detection, causing a minor recovery. This problem is solved here by irradiation during Hg preconcentration onto the photoactive dipstick, resulting in a limit of detection as low as 0.137 ng L^-1 using atomic fluorescence spectrometry (AFS). A 5 min preconcentration step is sufficient to obtain successful recovery of Hg traces from waters with up to 10 mg L^-1 DOC. The feasibility of the approach was demonstrated by the determination of Hg traces in Danube river water. The results show no significant differences in comparison with standard cold vapor-atomic fluorescence spectrometry (CV-AFS) measurements of the same sample. Hence, this new AuNP@TiO₂ dipstick provides a single-step sample preparation and preconcentration approach that combines sustainability with high analytical sensitivity and accuracy.