Ultratrace mercury speciation analysis in rice by in-line solid phase extraction - liquid chromatography - atomic fluorescence spectrometry

Ultrasensitive fluorescence sensor for Hg2+ in food based on three-dimensional upconversion nanoclusters and aptamer-modulated thymine-Hg2+-thymine strategy

Mercury (Hg²⁺) is a potentially toxic heavy metal ion found to be drastically deleterious to humans. Herein, an ultrasensitive fluorescence sensor was developed using three-dimensional upconversion nanoclusters (EBSUCNPs) and aptamer-modulated thymine-Hg²⁺-thymine strategy. The EBSUCNPs were used as the energy donors, the PDANPs served as the acceptors, and the aptamer was applied as an identification tag for Hg²⁺. Due to the energy transfer effect, the fluorescence of EBSUCNPs can be effectively quenched by Polydopamine nanoparticles (PDANPs). In the existence of Hg²⁺, T (thymine)-rich aptamers between EBSUCNPs and PDANPs were hybridized with Hg²⁺ to yield thymine-Hg²⁺-thymine and folded back to hairpin structure, causing PDANPs to detach from the EBSUCNPS and the recovery of fluorescence. Under optimum conditions, the linear sensing range of Hg²⁺ was 0.5-20 µg/L, and the detection limit was 0.28 µg/L. Furthermore, it exhibited excellent selectivity and anti-interference, which made it an ideal method for identifying Hg²⁺ in spiked samples.

Sulfur-Bridged Co(II)-Thiacalix[4]arene Metal-Organic Framework as an Electrochemical Sensor for the Determination of Toxic Heavy Metals

A novel sulfur-bridged metal-organic framework (MOF) [Co(TIC4R-I)_0.25Cl₂]·3CH₃OH (Co-TIC4R-I) based on thiacalix[4]arene derivatives was successfully obtained using a solvothermal method. Remarkably, adjacent TIC4R-I ligands were linked via Co(II) cations to form a three-dimensional (3D) microporous architecture. Subsequently, Co-TIC4R-I was modified on a glassy carbon electrode (Co-TIC4R-I/GCE) to produce an electrochemical sensor for the detection of heavy-metal ions (HMIs), namely, Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺, in aqueous solutions. It was found that Co-TIC4R-I/GCE exhibited wide linear detection ranges of 0.10-17.00, 0.05-16.00, 0.05-10.00, and 0.80-15.00 μM for Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺, respectively, in addition to low limit of detection (LOD) values of 0.017, 0.008, 0.016, and 0.007 μM. Moreover, the fabricated sensor employed for the simultaneous detection of these metals has achieved LOD values of 0.0067, 0.0027, 0.0064, and 0.0037 μM for Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺, respectively. The sensor also exhibited satisfactory selectivity, reproducibility, and stability. Furthermore, the relative standard deviation (RSD) values of Cd²⁺, Pb²⁺, Cu²⁺, and Hg²⁺ were 3.29, 3.73, 3.11, and 1.97%, respectively. Moreover, the fabricated sensor could sensitively detect HMIs in various environmental samples. The high performance of the sensor was attributed to its sulfur adsorption sites and abundant phenyl rings. Overall, the sensor described herein provides an efficient method for the determination of extremely low concentrations of HMIs in aqueous samples.