Methods for the determination of heavy metals in indocalamus leaves after different preservation treatment using inductively-coupled plasma mass spectrometry

Synergistic optical sensing of heavy metal ions using Mesua Ferrea derived carbon dot embedded Alginate based biopolymeric film as a sensor platform

Widespread environmental pollution from heavy metals poses severe health hazards, necessitating advanced detection methods. This study presents an innovative approach utilizing Mesua Ferrea Carbon Dots (MFCDs) incorporated biopolymeric nanocomposite films for optical identification of heavy metal ions (Fe3+, Cd2+, Hg2+, Pb2+, Cu2+). A blend of Na-Alginate and Agarose biopolymer was prepared as a matrix. Hydrothermally synthesized MFCDs possess negative zeta potential with their characteristic photoluminescence property. The MFCDs incorporated Na-Alginate-Agarose biopolymeric nanocomposite (MAA) film displayed enhanced hydrophilicity and UV absorption behaviour, showcasing its potential for optical detection of heavy metal ions. The optical analysis like fluorescence intensity and photoluminescence lifetime studies of the MAA film in response to heavy metal ions were thoroughly studied. The interaction dynamics highlighted specific metal ion quenching capabilities, emphasizing the potential of MFCDs coated film for sensitive heavy metal detection. The quenching mechanism for Fe3+ ions underscored the lowest level of detection in comparison with Cd2+, Hg2+, Pb2+ and Cu2+ ions, contributing to a comprehensive understanding of the optical detection phenomenon. Our research work provides a robust and scientifically validated solid platform for development of economically viable and environmentally benign optical sensor as an alternative of other existing methods for detection of heavy metal ions.

Micro-droplet printed ion-selective membrane sensors for in situ monitoring of marine heavy metal ions

Fast, accurate, and reliable techniques for marine toxic heavy metal ions (HMI) detection are critical for the ecological environment and human health. One of the fatal drawbacks of traditional ion selective electrochemical sensors is that the modification of electrode cannot be accurately quantified, resulting in poor repeatability of the detection electrode and large error between the multi-electrode detection results. In order to tackle this challenge, this study presents ultra-fine micro-droplet printed electrodes for the in-situ detection of Cd2+, a carcinogenic and toxic HMI commonly found in the ocean. The ion selective membrane casting liquid was dispersed into tiny droplets with a diameter of micron through microfluidic technology, and the microdroplets were precisely arranged on the electrode surface. As a result, the modification error of electrode was reduced to pL level (accurate to 10 pL), which greatly improved the repeatability between electrodes prepared in different batches. The results of experiments with pure electrolyte, interference ions and artificial seawater indicated that the micro-droplet printed sensors possessed excellent properties of accuracy, precision, repeatability, and anti-interference. This novel micro-droplet printed sensor has the potential to capture an accurate picture of nearshore HMI in heterogeneous environments under shock conditions.

Recent Advances in the Determination of Major and Trace Elements in Plants Using Inductively Coupled Plasma Optical Emission Spectrometry

Interest in measuring major and trace elements in plants has increased in recent years because of growing concerns about the elements' contribution to daily intakes or the health risks posed by ingesting vegetables contaminated by potentially toxic elements. The recent advances in using inductively coupled plasma atomic emission spectrometry (ICP-OES) to measure major and trace elements in plant samples are reviewed in the present work. The sample preparation before instrumental determination and the main advantages and limitations of ICP-OES are described. New trends in element extraction in liquid solutions using fewer toxic solvents and microextractions are observed in recently published literature. Even though ICP-OES is a well-established and routine technique, recent innovations to increase its performance have been found. Validated methods are needed to ensure the obtaining of reliable results. Much research has focused on assessing principal figures of merit, such as limits of detection, quantification, selectivity, working ranges, precision in terms of repeatability and reproducibility, and accuracy through spiked samples or certified reference materials analysis. According to the published literature, the ICP-OES technique, 50 years after the release of the first commercially available equipment, remains a powerful and highly recommended tool for element determination on a wide range of concentrations.

Nano-Needle Boron-Doped Diamond Film with High Electrochemical Performance of Detecting Lead Ions

Nano-needle boron-doped diamond (NNBDD) films increase their performance when used as electrodes in the determination of Pb2+. We develop a simple and economical route to produce NNBDD based on the investigation of the diamond growth mode and the ratio of diamond to non-diamond carbon without involving any templates. An enhancement in surface area is achievable for NNBDD film. The NNBDD electrodes are characterized through scanning electron microscopy, Raman spectroscopy, X-ray diffraction, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse anodic stripping voltammetry (DPASV). Furthermore, we use a finite-element numerical method to research the prospects of tip-enhanced electric fields for sensitive detection at low Pb2+ concentrations. The NNBDD exhibits significant advantages and great electrical conductivity and is applied to detect trace Pb2+ through DPASV. Under pre-deposition accumulation conditions, a wide linear range from 1 to 80 µgL-1 is achieved. A superior detection limit of 0.32 µgL-1 is achieved for Pb2+, which indicates great potential for the sensitive detection of heavy metal ions.

A Cascade Signal Amplification Strategy for the Ultrasensitive Fluorescence Detection of Cu2+ via λ-Exonuclease-Assisted Target Recycling with Mismatched Catalytic Hairpin Assembly

Herein, an ultrasensitive DNAzyme-based fluorescence biosensor for detecting Cu2+ was designed using the cascade signal amplification strategy, coupling λ-exonuclease-assisted target recycling and mismatched catalytic hairpin assembly (MCHA). In the designed detection system, the target, Cu2+, can activate the Cu2+-dependent DNAzyme to cause a cleavage reaction, releasing ssDNA (tDNA). Then, tDNA binds to hairpin DNA (H0) with an overhanging 5'-phosphorylated terminus to form dsDNA with a blunt 5'-phosphorylated terminus, which activates the dsDNA to be digested by λ-Exo and releases tDNA along with another ssDNA (iDNA). Subsequently, the iDNA initiates MCHA, which can restore the fluorescence of carboxyfluorescein (FAM) previously quenched by tetramethylrhodamine (TAMRA), resulting in a strong fluorescent signal. Furthermore, MCHA efficiently improves the signal-to-noise ratio of the detection system. More importantly, tDNA recycling can be achieved with the λ-Exo digestion reaction to release more iDNA, efficiently amplifying the fluorescent signal and further improving the sensitivity to Cu2+ with a detection limit of 60 fM. The practical application of the developed biosensor was also demonstrated by detecting Cu2+ in real samples, proving it to be an excellent analytical strategy for the ultrasensitive quantification of heavy metal ions in environmental water sources.

A portable microfluidic electrochemical sensing platform for rapid detection of hazardous metal Pb2+ based on thermocapillary convection using 3D Ag-rGO-f-Ni(OH)2/NF as a signal amplifying element

Heavy metal pollution is causing a great threat to ecological environment and public health, which needs an efficient strategy for monitoring. A portable microfluidic electrochemical sensing system was developed for the determination of heavy metal ions. Herein, the detection of Pb²⁺ was chosen as a model, and a microfluidic electrochemical sensing chip relying on a smartphone-based electrochemical workstation was proposed for rapid detection Pb²⁺ with the assistance of thermocapillary convection result from the formed temperature gradient. The 3D Ag-rGO-f-Ni(OH)₂/NF composites, prepared by one-step hydrothermal method without any Ni precursor salt, were used to further amplify electrochemical signals under the synergistic effect of thermocapillary convection. The thermocapillary convection could accelerate the preconcentration process and shorten the detection time (save 300 s of preconcentration time). The fabricated system exhibited the exceptional competence for monitoring of Pb²⁺ range from 0.01 μg/L to 2100 μg/L with a low detection limit (LOD) of 0.00464 μg/L. Furthermore, this portable system has been successfully demonstrated for detecting Pb²⁺ (0.01 μg/L to 2100 μg/L) in river water (LOD = 0.00498 μg/L), fish (LOD = 0.00566 μg/L) and human serum samples (LOD = 0.00836 μg/L), and the results were consistent with inductively coupled plasma-mass spectrometry (ICP-MS). The proposed novel sensing platform provides a cost-effectiveness, rapidly responding and ease-to-use pathway for analysis of heavy metal ions in real samples and shows great potential in point-of-care testing.

A novel copper(i) metal–organic framework as a highly efficient and ultrasensitive electrochemical platform for detection of Hg(ii) ions in aqueous solution

A novel copper(i) metal–organic framework was constructed and used to modify a glassy carbon electrode, and exhibits excellent electrochemical sensing of Hg(ii) ions.

Novel methodology for anodic stripping voltammetric sensing of heavy-metal ions using Ti3C2Tx nanoribbons

Conventional anodic stripping voltammetry (ASV) sensing of heavy-metal ions (HMIs) generally includes a two-step approach: (a) preconcentration via electrodeposition and (b) re-oxidation, while the requirement of the electrodeposition step makes the detection processes more complex. Herein, a novel methodology using self-reduction instead of electrodeposition was developed for the ASV sensing of HMIs (selecting Cd2+ as a representative analyte) by introducing Ti3C2Tx MXene nanoribbons (Ti3C2Tx NR) as a sensing element that can exhibit direct adsorption and reduction capabilities towards HMIs. Compared with conventional ASV technology, the proposed methodology is simpler and power-saving, and has a significant low detection limit (0.94 nM) and wide linear range (0.005-3.0 μM).

A 3D origami paper-based analytical device combined with PVC membrane for colorimetric assay of heavy metal ions: Application to determination of Cu(II) in water samples

Microfluidic paper-based analytical devices (μPADs) as a potentially powerful analytical platform have recently gained significant attention for on-site monitoring of heavy metal ions, which are one of the most significant environmental concern because of non-degradability and high toxicity. The commonly applied μPADs suffers from some defects, such as heterogeneous deposition of reagent, resulting in poor detection limits and low sensitivity. So, in this work, a three-dimensional origami μPAD combined with PVC Membrane was developed, which can manage problems of movement of colored products or leaching out the dye and leading to color heterogeneity in the detection zones. Furthermore, a waste layer was added to μPAD for loading of more amounts of the analyte, which results in improvement of detection limit. As a proof of concept, the μPAD was used for the analysis of Cu²⁺ ion. For this purpose, pyrocatechol violet and chrome azurol S as colorimetric reagents were doped into PVC membrane and injected in the detection zone. The proposed μPAD was presented good linearity in the ranges of 5.0-1400.0 and 5.0-200.0 mg L^-1, and the limits of detections of 1.7 and 1.9 mg L^-1 in presence of chrome azurol S and pyrocatechol violet, respectively.

Solid Sampling in Analysis of Various Plants Using Two-Jet Plasma Atomic Emission Spectrometry

The possibility of two-jet plasma atomic emission spectrometry for analysis of different plants using solid sample preparation and unified calibration samples was investigated. The certified reference materials of wheat, maize, rice, potato, grass mix, birch leaves, and Elodea canadensis were used for analysis. On the basis of the behavior of these plants in the plasma, they were divided into two groups: starch-containing materials (cereal and root crops) and leaves/grass. It was found that the previous sample carbonization should be used for analysis of starch-containing plants while leaves and grass could be analyzed by the direct technique. Carbonization was only applied for determining low concentrations of trace elements in leaves and grass. The calibration samples based on graphite powder and simple sample preparation, dilution of powdered sample with a spectroscopic buffer, were used for both direct analysis and analysis after carbonization. Such an approach allowed estimation of B, Ba, Be, Cd, Co, Cr, Cu, Ga, Fe, Mn, Ni, Pb, Si, Sr, V, and Zn in different plants. The limits of detection (LODs) provided by the direct technique were at the level of (µg·g^-1): n × 0.1 for Cd, Cu, and Mn; n for B, Ba, Co, Cr, Fe, Ga, Ni, Pb, Sr, V, and Zn; n × 10 for Si. Carbonization allowed improving LODs of elements several times depending on the thermal stability and mineral composition of plants. The LODs of elements in plants obtained after carbonization are the following (µg·g^-1): n × 0.01 for Be, Cd, Cu, and Mn; n × 0.1 for Co, Cr, Fe, Ga, Ni, Pb, Sr, V, Zn; and n for Si. The techniques suggested are fast, easily workable, and do not require harmful chemical reagents. In some cases, the influence of variable matrices and different element species on analytical signal of elements was not completely suppressed; the deviation of element concentrations from the true values was discussed.

Distribution, pollution, bioaccumulation, and ecological risks of trace elements in soils of the northeastern Qinghai-Tibet Plateau

Environmental quality of the northeastern Qinghai-Tibet Plateau has attracted more attention due to increasing anthropogenic disturbance. Therefore, this study investigated the distribution, pollution, ecological risks, and bioaccumulation of 12 target heavy metals and 16 rare earth elements (REEs) in soils of this area. The average concentrations of target trace elements in soils ranged from 0.16 (Hg) to 500.46 (Cr) mg/kg. Pb caused more serious pollution than the other elements based on geo-accumulation index evaluation. Hg exhibited the strongest enrichment feature with the average enrichment factor of 8.41. Compare with modified contamination degree and pollution load index, Nemerow pollution index method obtained the most serious evaluation results that 45.67% and 16.54% of sampling sites possessed high and moderate pollution. Evaluation results of potential ecological risk index showed that trace elements in soils posed very high and considerable ecological risks in 34.65% and 7.09% of sampling sites, respectively. Mining area was the region with the most serious pollution and ecological risks. Average bioaccumulation factor (BCF) values of target trace elements ranged from 0.05 (REEs) to 2.67 (Cr). Cr was the element that was easier to bio-accumulate in plants of the study area than the other target elements. It is in urgent need to take effective measures for controlling current pollution and potential ecological risks of trace elements in soils of the northeastern Qinghai-Tibet Plateau.