Direct magnetic sorbent sampling flame atomic absorption spectrometry (DMSS-FAAS) for highly sensitive determination of trace metals

Rapid solid-phase microProbing of soil and groundwater lead and cadmium by tuning hydrophilic and hydrophobic microenvironments

Soil and groundwater contamination by lead and cadmium poses significant environmental and health risks, necessitating the development of rapid and accurate field monitoring techniques, which are currently lacking. Although solid-phase colorimetric microProbing imaging offers a promising solution, fine-tuning the hydrophilic/hydrophobic microenvironment of lead or cadmium molecular sensors within the microProbing material is essential for achieving rapid and accurate detection. Here, we report a method to covalently bond xylenol orange (a lead sensor) or physically adsorb dithizone (a cadmium sensor) onto the hydrophilic or hydrophobic entities of TentaGel resins, enabling uniform sensor loading, selective sequestration, and rapid microProbing of soil and groundwater lead or cadmium. Through microenvironment fine-tuning, the method achieved high sensitivity, with detection limits of 28 ppm and 9.9 ppb for soil and groundwater lead, and 50 ppb and 6.8 ppb for soil and groundwater cadmium, respectively. It accurately detected soil and groundwater lead from an economic development zone in Shenzhou (Hebei Province) and cadmium from a mine in Daye (Hubei Province), China. A portable microProbing device was also custom-designed and fabricated. With this device, the microProbing method shows great promise for field monitoring of other heavy metals in contaminated lands.

A rapid and specific fluorescent probe based on ESIPT-AIE-active for copper ion quantitative detection in food and environmental samples

In the field of food safety, the identification and measurement of active components in food is a pressing issue. The concentration of copper ions (Cu2+) in the environment is closely linked to food safety, and overall biological health. Therefore, developing rapid and accurate analytical techniques to monitor Cu2+ in food is of great significance. In this study, two fluorescent probes L-2 and L-3 were synthesized through a simple Schiff base condensation reaction. And L-3 demonstrated better anti-interference ability to Cu2+ than that of L-2. Meanwhile, spectroscopic experiments showed that L-3 possessed an extremely low detection limit (LOD) and low limits of quantification (LOQ) (LOD = 92.79 nM, LOQ = 309.33 nM), and quickly respond time (<30 s). Probe L-3 for monitoring effectively quantitatively identified Cu2+ in food and environmental samples, achieving an accuracy rate ranging from 84.42% to 117.45% and precision with a relative standard deviation (RSD) of less than 6.0%. The accuracy had been validated using the inductively coupled plasma-mass spectrometry (ICP-MS). Simultaneously, a WeChat Mini Program has been developed to detect total copper content in food samples based on fluorescence values, enabling consumers to evaluate food safety more intuitively. Moreover, L-3 also facilitated the quantitative visualization of Cu2+ in biological systems, underscoring its compatibility and practicality.

A Reliable and Straightforward Combination of vortex-assisted Dispersive Magnetic solid-phase Extraction with Direct Sorbent Sampling for Highly Sensitive Silver Determination in Water Samples Using Flame and Metal Furnace AAS

In the present paper, the assessment of vortex-assisted dispersive magnetic solid-phase extraction using amino-functionalized mesoporous combined with direct magnetic sorbent sampling (DMSS) in flame or furnace atomic absorption spectrometry (FAAS or FF-AAS) was demonstrated for highly sensitive silver determination in water samples. The developed method showed significant enrichment factors compared to conventional pneumatic nebulization by FAAS, 607 for DMSS-FF-AAS and 114 for DMSS-FAAS. The analytical curve showed linearity in the range from 5.0 to 70.0 µg L- 1 and 1.0 to 15.0 µg L- 1 and limits of detection of 0.59 and 0.09 µg L- 1 for DMSS-FAAS and DMSS-FF-AAS, respectively. The intra and inter-day precision evaluated as a percentage of the relative standard deviation (RSD,%) ranged from 1.89 to 4.71% for levels of 25.0 and 65.0 µg L- 1. The method was applied in different kinds of water samples without matrix effects, yielding recovery values from 90 to 110%.

Fluorescence/colorimetric dual-signal sensor based on carbon dots and gold nanoparticles for visual quantification of Cr3

A convenient and sensitive dual-signal visualization method is constructed for detection of trivalent chromium ions (Cr3+) based on fluorescent carbon dots (CDs) and glutathione-modified gold nanoparticles (GSH-Au NPs). The fluorescence of CDs can be quenched by GSH-Au NPs due to the inner filter effect. Cr3+ induces aggregation of GSH-Au NPs because of the coordination with GSH on the surface of Au NPs, leading to the red shift of surface plasmon resonance absorption of Au NPs that provides a "turn-on" fluorescence and colorimetric assay for Cr3+. The fluorescence/colorimetric dual signal detection shows high sensitivity for Cr3+ with wide detection linear ranges (0.5-70 μM for fluorescence detection and 2-50 μM for colorimetric detection) and low detection limits (0.31 μM for fluorescence detection and 0.30 μM for colorimetric detection). Besides, the method has high selectivity for Cr3+ and can be used for detection of Cr3+ in lake water and tap water samples, showing great potential for visual detection of environmental Cr3+.

A novel deep eutectic solvent modified magnetic covalent organic framework for the selective separation and determination of trace copper ion in medicinal plants and environmental samples

BACKGROUND

Pretreatment techniques should be introduced before metal ion determination because there is very low content of heavy metals in Chinese medicinal plants and environmental samples. Magnetic dispersive micro solid phase extraction (MDMSPE) has been widely used for the separation and adsorption of heavy metal pollutants in medicinal plants and environmental samples. However, the majority of MDMSPE adsorbents have certain drawbacks, including low selectivity, poor anti-interference ability, and small adsorption capacity. Therefore, modifying currently available adsorption materials has gained attention in research.

RESULTS

In this study, a novel adsorbent MCOF-DES based on a magnetic covalent organic framework (MCOF) modified by a new deep eutectic solvent (DES) was synthesized for the first time and used as an adsorbent of MDMSPE. The MDMSPE was combined with inductively coupled plasma optical emission spectrometry (ICP-OES) for selective separation, enrichment, and accurate determination of trace copper ion (Cu2+) in medicinal plants and environmental samples. Various characterization results show the successful preparation of new MCOF-DES. Under the optimal conditions, the enrichment factor (EF) of Cu2+ was 30, the limit of detection (LOD) was 0.16 μg L-1, and the limit of quantitation (LOQ) was 0.54 μg L-1. The results for the determination of Cu2+ were highly consistent with those of inductively coupled plasma mass spectrometry (ICP-MS), which verified the accuracy and reliability of the method.

SIGNIFICANCE

The established method based on a new adsorption material MCOF-DES has achieved the selective separation and determination of trace Cu2+ in medicinal and edible homologous medicinal materials (Phyllanthus emblica Linn.) and environmental samples (soil and water), which provides a promising, selective, and sensitive approach for the determination of trace Cu2+ in other real samples.

Room temperature cost-effective synthesis of carbon quantum dots for fluorescence pattern recognition of metal ions

Herein, a type of low-consuming carbon quantum dot (CD) has been synthesized at room temperature in just 45 minutes via Schiff base reaction between o-phthalaldehyde (OPA) and polyethyleneimine (PEI). These CDs are pH-dependent, so a novel label-free florescent sensor array can be constructed by utilizing buffers with various pH levels, which leads to distinctive fluorescence response patterns upon being challenged with metal ions for their pattern recognition. The results demonstrate that large-scale detection of metal ions can be achieved with as little as 3 types of sensors. Additionally, the sensors are able to discriminate between various metal ion concentrations and mixtures of different metal ions. The technique demonstrates potential uses in water quality monitoring by promising straightforward, quick, sensitive, and potent discrimination of metal ions.