Mercury speciation in seawater by liquid chromatography-inductively coupled plasma-mass spectrometry following solid phase extraction pre-concentration by using an ionic imprinted polymer based on methyl-mercury–phenobarbital interaction

Color-reversible fluorescence tracking for the dynamic interaction of SO2 with Hg2+ in living cells

Mercury ion (Hg2+) is one of the most threatening substances to human health, and the mercury poisoning can damage physiological homeostasis severely in human, even cause death. Intriguingly, Sulfur dioxide (SO2), a gas signal molecule in human, can specifically interact with Hg2+ for relieving mercury poisoning. However, the dynamic interaction of Hg2+ with SO2 at the tempospatial level and the correlation between Hg2+ and SO2 in the pathological process of mercury poisoning are still elusive. Herein, we rationally designed a reversible and dual color fluorescent probe (CCS) for dynamically visualizing Hg2+ and SO2 and deciphering their interrelationship in mercury poisoning. CCS held good sensitivity, selectivity and reversibility to Hg2+ and SO2, that enabled CCS to specifically detect SO2 and Hg2+ via cyan fluorescence channel (centered around 485 nm) and red fluorescence channel (centered around 679 nm), respectively. Notably, the separate fluorescence signal changes of CCS realized the dynamic tracing of Hg2+ and SO2 in living cells, and presented the potential for exploring the correlation between SO2 and Hg2+ in mercury poisoning.

Advancements in mercury detection using surface-enhanced Raman spectroscopy (SERS) and ion-imprinted polymers (IIPs): a review

Mercury (Hg) contamination remains a major environmental concern primarily due to its presence at trace levels, making monitoring the concentration of Hg challenging. Sensitivity and selectivity are significant challenges in the development of mercury sensors. Surface-enhanced Raman spectroscopy (SERS) and ion-imprinted polymers (IIPs) are two distinct analytical methods developed and employed for mercury detection. In this review, we provide an overview of the key aspects of SERS and IIP methodologies, focusing on the recent advances in sensitivity and selectivity for mercury detection. By examining the critical parameters and challenges commonly encountered in this area of research, as reported in the literature, we present a set of recommendations. These recommendations cover solid and colloidal SERS substrates, appropriate Raman reporter/probe molecules, and customization of IIPs for mercury sensing and removal. Furthermore, we provide a perspective on the potential integration of SERS with IIPs to achieve enhanced sensitivity and selectivity in mercury detection. Our aim is to foster the establishment of a SERS-IIP hybrid method as a robust analytical tool for mercury detection across diverse fields.

Polymeric Materials in Speciation Analysis Based on Solid-Phase Extraction

Speciation analysis is a relevant topic since the (eco)toxicity, bioavailability, bio (geo)chemical cycles, and mobility of a given element depend on its chemical forms (oxidation state, organic ligands, etc.). The reliability of analytical results for chemical species of elements depends mostly on the maintaining of their stability during the sample pretreatment step and on the selectivity of further separation step. Solid-phase extraction (SPE) is a matter of choice as the most suitable and widely used procedure for both enrichment of chemical species of elements and their separation. The features of sorbent material are of great importance to ensure extraction efficiency from one side and selectivity from the other side of the SPE procedure. This review presents an update on the application of polymeric materials in solid-phase extraction used in nonchromatographic methods for speciation analysis.

An improved method for rapid and safe preparation and measurement of dimethylmercury using gas chromatography-atomic fluorescence spectrometry

Transformations between dimethylmercury (DMHg) and other mercury (Hg) species have been one of the critical knowledge gaps in the Hg global biogeochemical cycle due to the lack of detailed studies. The preparation and measurement of DMHg are challenging due to the high toxicity and volatility of DMHg. In this work, we invented a new DMHg generator for successfully preparing high-purity DMHg in a highly controllable and safe way. The DMHg could be spontaneously volatilized and diffused from the original preparation solution to the solution to be studied. The parameters for generating DMHg were optimized to be the pH value of 4.0 with a MeCo/Hg2+ molar ratio of 10 at 20 °C. The following measurement method of DMHg in the presence of various species of Hg was also investigated and optimized. Hg0 and DMHg could be separated effectively with the carrier gas flow rate of 15 mL min-1 and the gas chromatography column temperature of 30 °C. The interferences of Hg0, monomethylmercury and other species were excluded by systematic control experiments. A sensitive and reliable approach for quantifying trace DMHg in water was developed. Under the optimal conditions, the limits of detection for Hg0, MMHg and DMHg were 0.03, 0.002 and 0.024 ng L-1, respectively, with the relative standard deviation below 8.2%. The developed method was validated by the determination Hg species of different natural water samples. This work is expected to provide a new and safe strategy for DMHg preparation and a verified method for DMHg measurement.

Preconcentration and speciation analysis of mercury: 3D printed metal scavenger-based solid-phase extraction followed by analysis with inductively coupled plasma mass spectrometry

A selective method for preconcentration and determination of methylmercury (MeHg) and inorganic mercury (iHg) in natural water samples at the ng L^-1 level has been developed. The method involves adsorption of Hg species into a 3D printed metal scavenger and sequential elution with acidic thiourea solutions before ICP-MS determination. Experimental parameters affecting the preconcentration of MeHg and iHg such as the sample matrix, effect of the flow rate on adsorption, eluent composition, and elution mode have been studied in detail. The obtained method detection limits, considering the preconcentration factors of 42 and 93, were found to be 0.05 ng L^-1 and 0.08 ng L^-1 for MeHg and iHg, respectively. The accuracy of the method was assessed with a certified groundwater reference material ERM-CA615 (certified total iHg concentration 37 ± 4 ng L^-1). The determined MeHg concentration was below MDL while iHg concentration was determined to be 41.2 ± 0.5 ng L^-1. Both MeHg and iHg were also spiked to natural water samples at 5 ng L^-1 concentration and favorable spiking recoveries of 88-97% were obtained. The speciation procedure was successfully applied to two lake water samples where MeHg and iHg concentrations ranged from 0.18 to 0.24 ng L^-1 and 0.50-0.62 ng L^-1, respectively. The results obtained demonstrate that the developed 3D printed metal scavenger-based method for preconcentration and speciation of Hg is simple and sensitive for the determination of Hg species at an ultra-trace level in water samples.

Preparation of environmental samples for chemical speciation of metal/metalloids: A review of extraction techniques

Chemical speciation is a relevant topic in environmental chemistry since the (eco)toxicity, bio (geo)chemical cycles, and mobility of a given element depend on its chemical forms (oxidation state, organic ligands, etc.). Maintaining the chemical stability of the species and avoiding equilibrium disruptions during the sample treatment is one of the biggest challenges in chemical speciation, especially in environmental matrices where the level of concomitants/interferents is normally high. To achieve this task, strategies based on chemical properties of the species can be carried out and pre-concentration techniques are often needed due to the low concentration ranges of many species (μg L^-1 - ng L^-1). Due to the significance of the topic and the lack of reviews dealing with sample preparation of metal (loid)s (usually, sample preparation reviews focus on the total metal content), this work is presented. This review gives an up-to-date overview of the most common sample preparation techniques for environmental samples (water, soil, and sediments), with a focus on speciation of metal/metalloids and determination by spectrometric techniques. Description of the methods is given, and the most recent applications (last 10 years) are presented.

Rational Design of an Ion-Imprinted Polymer for Aqueous Methylmercury Sorption

Methylmercury (MeHg+) is a mercury species that is very toxic for humans, and its monitoring and sorption from environmental samples of water are a public health concern. In this work, a combination of theory and experiment was used to rationally synthesize an ion-imprinted polymer (IIP) with the aim of the extraction of MeHg+ from samples of water. Interactions among MeHg+ and possible reaction components in the pre-polymerization stage were studied by computational simulation using density functional theory. Accordingly, 2-mercaptobenzimidazole (MBI) and 2-mercaptobenzothiazole (MBT), acrylic acid (AA) and ethanol were predicted as excellent sulfhydryl ligands, a functional monomer and porogenic solvent, respectively. Characterization studies by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) revealed the obtention of porous materials with specific surface areas of 11 m2 g-1 (IIP-MBI-AA) and 5.3 m2 g-1 (IIP-MBT-AA). Under optimized conditions, the maximum adsorption capacities were 157 µg g-1 (for IIP-MBI-AA) and 457 µg g-1 (for IIP-MBT-AA). The IIP-MBT-AA was selected for further experiments and application, and the selectivity coefficients were MeHg+/Hg2+ (0.86), MeHg+/Cd2+ (260), MeHg+/Pb2+ (288) and MeHg+/Zn2+ (1510), highlighting the material's high affinity for MeHg+. The IIP was successfully applied to the sorption of MeHg+ in river and tap water samples at environmentally relevant concentrations.

Mercury speciation in edible seaweed by liquid chromatography - Inductively coupled plasma mass spectrometry after ionic imprinted polymer-solid phase extraction

In contrast to most of essential and heavy metals, mercury levels in seaweed are very low, and pre-concentration methods are required for an adequate total mercury determination and mercury speciation in this foodstuff. An ionic imprinted polymer-based solid phase extraction (on column) pre-concentration procedure has been optimized for mercury species enrichment before liquid chromatography hyphenated with inductively coupled plasma mass spectrometry determination. The polymer has been synthesized by the precipitation polymerization method and using a ternary pre-polymerization mixture containing the template (methylmercury), a non-vinylated monomer (phenobarbital), and a vinylated monomer (methacrylic acid). Factors affecting the adsorption/desorption of Hg species (extract pH, loading and elution flow rates, volume of eluent, etc.), and parameters such as breakthrough volume and reusability, were fully studied. Mercury species were first isolated from seaweed by ultrasound assisted extraction using a 0.1% (v/v) HCl, 0.12% (w/v) l-cysteine, 0.1% (v/v) mercaptoethanol solution. Under optimized conditions, the limits of detection were 0.007 and 0.02 μg kg^-1 dw for methylmercury and Hg(II), respectively. The pre-concentration factor (volume of 10 mL of seaweed extract) was 50. Repeatability and reproducibility of the method were satisfactory with relative standard deviations lower than 16%. The proposed methodology was finally applied for the selective pre-concentration and determination of methylmercury and Hg (II) in a BCR-463 certified reference material and in several edible seaweeds.

A Critical Review on the Synthesis and Application of Ion-Imprinted Polymers for Selective Preconcentration, Speciation, Removal and Determination of Trace and Essential Metals from Different Matrices

The presence of toxic trace metals and high concentrations of essential elements in the environment presents a serious threat to living organism. Various methods have been used for the detection, preconcentration and remediation of these metals from biological, environmental and food matrices. Owing to the complexicity of samples, methods with high selectivity have been used for detection, preconcentration and remediation of these trace metals. These methods are achieved by the use of ion-imprinted polymers (IIPs) due to their impressive properties such as selectivity, high extraction efficiency, speciation capability and reusability. Because of the increase of toxic trace and essential metals in the environment, IIPs have attracted great use in analytical chemistry. This review, provide a brief background on IIPs and polymerization method that are used for their preparation. Recent applications of IIPs as adsorbents for preconcentration, removal, speciation and electrochemical detection of trace and essential metal is also discussed.

Preparation of a new magnetic ion-imprinted polymer and optimization using Box-Behnken design for selective removal and determination of Cu(II) in food and wastewater samples

A new magnetic Cu(II) IIP (Fe₃O₄@IIP-IDC) is synthesized by polymerization of Imidazole-4,5-dicarboxylic acid functionalized Allyl chloride, and significant improvement of its performance has been compared. SPE parameters were optimized using Box-Behnken design to achieve the twin objectives of quantitative determination and removal of Cu(II). FLPSO kinetic model and BS isotherm model fits well with the capacity of 175 mg g^-1. Analytical figures of merit includes a linearity range of 10-5,000 µg L^-1 (R² = 0.9986), preconcentration factor of 50 after eluting with 5 mL of 1 M HNO₃, LOD of 1.03 µg L^-1 and LOQ of 4.5 µg L^-1. Accuracy was assessed by analysis of SRM (Standard Reference Material) and recovery experiments after spiking in food samples (Tea, coffee, chocolate, spinach, infant milk substitute) and battery wastewater. Ease of use, reusability (15 cycles), rapid adsorption and high selectivity makes it a promising candidate for efficient and selective removal and trace determination.

Sensor-as-a-Service: Convergence of Sensor Analytic Point Solutions (SNAPS) and Pay-A-Penny-Per-Use (PAPPU) Paradigm as a Catalyst for Democratization of Healthcare in Underserved Communities

In this manuscript, we discuss relevant socioeconomic factors for developing and implementing sensor analytic point solutions (SNAPS) as point-of-care tools to serve impoverished communities. The distinct economic, environmental, cultural, and ethical paradigms that affect economically disadvantaged users add complexity to the process of technology development and deployment beyond the science and engineering issues. We begin by contextualizing the environmental burden of disease in select low-income regions around the world, including environmental hazards at work, home, and the broader community environment, where SNAPS may be helpful in the prevention and mitigation of human exposure to harmful biological vectors and chemical agents. We offer examples of SNAPS designed for economically disadvantaged users, specifically for supporting decision-making in cases of tuberculosis (TB) infection and mercury exposure. We follow-up by discussing the economic challenges that are involved in the phased implementation of diagnostic tools in low-income markets and describe a micropayment-based systems-as-a-service approach (pay-a-penny-per-use—PAPPU), which may be catalytic for the adoption of low-end, low-margin, low-research, and the development SNAPS. Finally, we provide some insights into the social and ethical considerations for the assimilation of SNAPS to improve health outcomes in marginalized communities.

Benefit-risk assessment of commonly consumed fish species from South China Sea based on methyl mercury and DHA

Even though a growing number of reports indicated favorable health effects with fish consumption, kinds of hazardous substances in fish were detected in fish and to be exceeded advisory limitation. Benefit-risk assessment of commonly consumed fish is urgently needed. We conducted fish consumption survey and fish sampling in the coast of South China Sea to assess benefit-risk effect of commonly consumed fish species. For local residents, weekly methyl mercury (MeHg) exposures from commonly consumed fish species ranged from 0.12 to 2.11 μg/kg bw. Apart from Muraenesox cinereus and Acanthopagrus latus, the rest of 92% (23/25) fish species were at low risk of MeHg exposure. Daily docosahexaenoic acid intakes via consuming specific fish were between 42.18 and 1687.04 mg/day. A total of 72% (18/25) fish species could provide 200 mg/day of DNA for local residents. Benefit-risk assessment assuming intelligence quotient (IQ) score model showed net IQ point gains between 1.53 and 5.65 points with consuming various fish species, indicative of large distinction of health benefit from various fish species. This study suggests commonly consumed fish species from China South Sea could bring much more positive effect than negative effect. Species-specific fish should be considered when providing recommendations of fish consumption. Muraenesox cinereus and Acanthopagrus latus should be minded with risk of MeHg exposure in taking large amounts.

Removal of inorganic mercury by selective extraction and coprecipitation for determination of methylmercury in mercury-contaminated soils by chemical vapor generation inductively coupled plasma mass spectrometry (CVG-ICP-MS)

A procedure is developed for selective extraction of methylmercury (CH₃Hg⁺) from heavily Hg-contaminated soils and sediments for determination by chemical vapor generation inductively coupled plasma mass spectrometry (CVG-ICP-MS). Soils artificially contaminated with 40 μg g^-1 inorganic mercury (Hg²⁺) or methylmercury chloride (CH₃HgCl) were agitated by shaking or exposing to ultrasounds in dilute hydrochloric acid (HCl) or nitric acid (HNO₃) solutions at room temperature. Extractions in HCl (5 or 10% v/v) resulted in substantial leaching of Hg²⁺ from soils, whereas 5% (v/v) HNO₃ provided selectivity for quantitative extraction of CH₃Hg⁺ with minimum Hg²⁺ leaching. Agitation with ultrasounds in 5% (v/v) HNO₃ for about 3 min was sufficient for extraction of all CH₃Hg⁺ from soils. Coprecipitations with Fe(OH)₃, Bi(OH)₃ and HgS were investigated for removal of residual Hg²⁺ in soil extracts. Hydroxide precipitations were not effective. Thiourea or l-cysteine added to soil extracts prior to hydroxide precipitation improved precipitation of Hg²⁺, but also resulted in removal of CH₃Hg⁺. HgS precipitation was made with dilute ammonium sulfide solution, (NH₄)₂S. Adding 30 μL of 0.35 mol L^-1 (NH₄)₂S to soil extracts in 5% (v/v) HNO₃ resulted in removal of all residual Hg²⁺ without impacting CH₃Hg⁺ levels. Vapor generation was carried out by reacting Hg²⁺-free soil extracts with 1% (m/v) NaBH₄. No significant interferences were observed from (NH₄)₂S on the vapor generation from CH₃Hg⁺. The slopes of the calibration curves for CH₃HgCl standard solutions in 5% (v/v) HNO₃ with and without (NH₄)₂S were similar. Limits of detection (LOD, 3s method) were around 0.08 μg L^-1 for 5% (v/v) HNO₃ blanks (n = 10) and 0.10 μg L^-1 for 5% (v/v) HNO₃ + 0.005 mol L^-1 (NH₄)₂S blanks (n = 10). Percent relative standard deviation (%RSD) for five replicate measurements varied between 3.1% and 6.4% at 1.0 CH₃HgCl level. The method is validated by analysis of two certified reference materials (CRM); purely Methylmercury sediment (SQC1238, 10.00 ± 0.291 ng g^-1 CH₃Hg⁺) and Hg-contaminated Estuarine sediment (ERM - CC580, 75 ± 4 ng g^-1 CH₃Hg⁺ and 132 ± 3 μg g^-1 total Hg). CH₃Hg⁺ values for SQC1238 were between 13.0 and 13.2 ng g^-1, and 79 and 81 ng g^-1 for ERM - CC580. Hg-contaminated soils (57-96 μg g^-1 total Hg) collected from the floodplains of Oak Ridge, TN were analyzed for CH₃Hg⁺ using the procedure by CVG-ICPMS. CH₃Hg⁺ levels ranged from 30 to 51 ng g^-1 and did not correlate with total Hg levels (R² = 0.01).

A Review on Recent Applications of High-Performance Liquid Chromatography in Metal Determination and Speciation Analysis

High-performance liquid chromatography (HPLC) has several advantages over the conventional methods due to their operational simplicity. It is a vital tool to determine metal ions having same mass but different electronic configuration, to separate complex mixtures and to resolve ions that may be indistinguishable by mass spectrometry alone. Metal ions play vital role in many biological processes and involved in setting up of many diseases. Therefore, the development of simple methods for the detection and quantification of metals in real samples might serve as diagnostic tools for various diseases. This review article focuses on the recent main feature of this technique, i.e. speciation of metal ions and their applications to series of problem of metal ion chemistry in different environmental matrixes. Speciation of metals is of increasing interest and has a great importance because of bioavailability, environmental mobility, toxicity and potential risk of metals. With the capability of partitioning the complex species of different metal ions, HPLC is an efficient technique for this task. This review summarizes recent advances in the development of HPLC to the fundamental understanding of metal ion chemistry in the environment and discusses all the issues that still need a lot of consideration. It has been classified into different sections depending on the role of HPLC in separation used and metal speciation; furthermore, the underlying sample preconcentration techniques and detection systems involved for the determination of metal ions and their applications were discussed.

Microwave-assisted synthesis of bovine serum albumin–gold nanoclusters and their fluorescence-quenched sensing of Hg2+ ions

Fluorescence sensing of Hg²⁺ ions by BSA–Au NCs based on the metallophilic interaction between Hg²⁺ and Au⁺ ions.

A novel ion imprinted SiO2 microsphere for the specific and rapid extraction and pre-concentration of ultra-trace methyl mercury

A novel MeHg ion imprinted silica microsphere was designed and synthesized for the specific, cost-effective and rapid pre-concentration of ultra-trace MeHg from natural water.

Synthesis of ion imprinted polymeric nanoparticles for selective pre-concentration and recognition of lithium ions

A new Li⁺–IIP has been prepared for the fast determination and selective separation of lithium ions in aqueous samples.