Detection Of Trace Mercury Research Articles

Solid-Phase Microextraction Mediated Solid-Phase Dielectric Barrier Discharge Vapor Generation-Atomic Fluorescence Spectrometry for Sensitive Determination of Mercury in Seawater.

A novel method coupling solid-phase microextraction (SPME) to solid-phase dielectric barrier discharge (SPDBD) vapor generation was proposed and used for the sensitive detection of trace mercury (Hg) in seawater with atomic fluorescence spectrometry (AFS) in this work. The method proposed herein offers the unique advantages of integrating desorption and chemical vapor generation into one step, eliminating the use of elution reagents, and reducing the analysis time. SPME with multiwalled carbon nanotubes (MWCNTs) coated on the glass tube was used to extract Hg2+ in seawater. The Hg2+ was then desorbed and reduced to Hg0 vapor by SPDBD, which was detected by cold vapor AFS. The parameters affecting Hg2+ extraction, desorption, and vapor generation were studied. The detection limit of Hg2+ was 0.0003 μg L-1, and the relative standard deviation at a Hg2+ concentration of 0.05 μg L-1 was 4.4%. This method also has excellent antimatrix interference ability for Hg2+ determination with recoveries between 91.8% and 101.1% in the presence of extremely high concentrations (two million times excess) of coexisting ions. The practicality of this method was also evaluated by analyzing two different certified reference materials of Hg2+ in water and several seawater samples with good spike recoveries (94.0%-107.4%). Compared with solid-phase photothermo-induced vapor generation, this method has higher extraction efficiency and higher desorption efficiency without the assistance of heating as well as a lower detection limit of Hg2+, which is capable of performing trace Hg analysis in seawater.

Unique three-dimensional ordered macroporous dealloyed gold-silver electrochemical sensing platforms for ultrasensitive mercury(II) monitoring.

To address the requirement of ultra-sensitive detection of trace mercury(II) (Hg2+) ions in the environment and food, we developed an electrochemical biosensor with super-sensitivity, extremely high selectivity, and reusability. This biosensor comprised two signal amplification components: a three-dimensional macroporous dealloyed (3DOMD) Au-Ag thin-film electrode and a multifunctional encoded Au@Pt nanocage (APNC). As a platform for immobilized capture DNA (cDNA), a 3DOMD Au-Ag thin film prepared by a dealloying method with an active surface area 4.8 times higher than that of 3D macroporous gold films generated by cyclic voltammetry (CV) with sulfuric acid was capable of increasing the sensing surface area while also strengthening the electron transport capacity of the sensing substrate due to its multilayered multi-porous framework. In the presence of Hg2+, probe DNA (pDNA) could be hybridized with the mismatched capture DNA (cDNA) through stable thymine-Hg2+-thymine (T-Hg2+-T) linkages, connecting thionine-APNC to the electrode surface and utilizing the large specific surface area to accomplish highly sensitive detection of Hg2+. With an extremely low Hg2+ detection limit of 2 pM and a detection range from 0.01 to 1000 nM, this technique opened up a new avenue for the ultrasensitive detection of a wider range of heavy metal ions or biomolecules.

Hierarchical porous loofah-like carbon with sulfhydryl functionality for electrochemical detection of trace mercury in water

Mercury is a common contaminant found in natural waters, which is highly toxic to human health. Thus, the facile and reliable monitoring of mercury in waters is of great significance. In this study, we fabricated a novel loofah-like hierarchical porous carbon with sulfhydryl functionality (S-LHC), and applied it as an ultrasensitive sensor for the electrochemical detection of mercury in water. The S-LHC was prepared through the direct pyrolysis of a triazole-rich metal-organic framework (MOF), followed by chemical modification using thioglycolic acid. The highly conductive N-doped carbon framework of S-LHC facilitated the electron transfer in mercury electrochemical sensing. Meanwhile, the open hierarchical pore structure and abundant sulfhydryl groups allowed the fast diffusion and effective enrichment of mercury ions. Consequently, the S-LHC sensor exhibited an exceptionally high sensitivity for mercury ions, with the mercury detection limit (0.36 nM) orders of magnitude lower than the regulated values in drinking water (typically 10∼30 nM). The constructed sensor also afforded good anti-interference ability and excellent stability for long-term detection of mercury in a variety of complex real water samples. The present study provides not only a facile method for mercury detection, but also a new idea for the construction of highly sensitive electrochemical sensors.

Boron-Doped Diamond Modified with 4-Mercaptopyridine-Functionalized Gold Nanoparticles for Trace Mercury Detection

Boron-Doped Diamond Modified with 4-Mercaptopyridine-Functionalized Gold Nanoparticles for Trace Mercury Detection

Thiol-grafted covalent organic framework-based electrochemical platforms for sensitive detection of Hg(II) ions.

Triazine-based covalent organic frameworks functionalized by thiol and thioether (COFS-CH3/COFS-SH) were designed and served as a platform that could bind with mercury ions specifically based on Hard-Soft-Acid-Base theory. As such, when employing COFs as a modifier in a carbon paste electrode (CPE), the COFS-CH3-modified CPE revealed an extraordinary performance (detection limit of 0.01 ppb; linear range of 0.1 to 1.0 ppb) and repeatability for electrochemical detection of trace mercury, even in real samples collected from tap or lake water. This innovative approach leverages the inherent properties of covalent organic frameworks (COFs) to enable highly sensitive and selective detection of target analytes.

A triphenylamine-based fluorescent probe with phenylboronic acid for highly selective detection of Hg2+ and CH3Hg+ in groundwater.

Mercury is a highly toxic heavy metal and it poses a serious threat to the natural environment and human health. Thus, selective detection of trace mercury (e.g. inorganic mercury and methylmercury) in the environment is critical yet challenging. Herein, we describe the rational design and facile synthesis of a new triphenylamine-based phenylboronic acid fluorescent probe (TPA-PBA) for selective detection of Hg2+ and CH3Hg+. Due to the inherent specificity of the displacement reaction between phenylboronic acid and mercury, this probe exhibits exceptionally high selectivity towards Hg2+/CH3Hg+ against other tested ions with ppb-level sensitivity. More importantly, the probe TPA-PBA is effective and selective in detecting Hg2+/CH3Hg+ in tap water and real-world groundwater, indicating its potential practical applications in in situ and online mercury detection in real-world scenarios. With TPA-PBA based test strips Hg2+ can be distinguished from CH3Hg+ by the naked eye. This study could accelerate the development of low-cost, highly efficient and selective fluorescent probes for rapid trace mercury detection.

Modified MSIS chamber as a novel gas–liquid separator coupled with the photochemical vapor generation of trace mercury with MP-AES detection

A modified MSIS chamber operating with high sample flow rates was used as a novel gas–liquid separator in the MP-AES detection of trace mercury after photochemical vapor generation.

Electrochemical sensor based on MoS2 nanosheets and DNA hybridization for trace mercury detection

• Chitosan/GO/MoS 2 /AuNPs and T-Hg 2+ -T base pair were used to form an electrochemical sensor with low detection limit, good repeatability, and specificity. • MoS 2 nanosheets were used as a substrate for the immobilization of DNA and amplified the electrochemical signal produced by the sensor. • A novel electrochemical method for trace Hg 2+ detection in water was developed. Mercury ions (Hg 2+ ) are highly toxic and can cause serious harm to the environment and human health. In this study, we prepared a novel electrochemical sensor based on an electrode coated with chitosan/graphene oxide/molybdenum disulfide/Au nanoparticles (chitosan/GO/MoS 2 /AuNPs) and thymine-Hg 2+ -thymine base pair to detect trace Hg 2+ in water. This method effectively utilized the affinity of MoS 2 to immobilize deoxyribonucleic acid (DNA) on the electrode surface and enabled the amplification of the electrochemical signals detected by the sensor. The specific binding of the thymine-Hg 2+ -thymine base pair and the electrochemical activity of MoS 2 successfully reduced the detection limit of Hg 2+ and rendered it interference resistant. In the presence of Hg 2+ , a double-stranded structure was formed on the electrode after the interaction between Hg 2+ and DNA, which caused the change of the oxidation current signal of the electrode surface. The sensor showed good linearity ranging from 0.01 μg/L to 4 μg/L with a correlation coefficient of 0.991, and the limit of detection was found to be 5.8 ng/L. This portable chitosan/GO/MoS 2 /AuNPs modified electrode showed satisfactory recovery in tap water samples, thus demonstrating its potential for application in trace Hg 2+ detection.

Synthesis and Characterization of Ru-MOFs on Microelectrode for Trace Mercury Detection.

Mercury ions (Hg) pollution in the water environment can cause serious harm to human health. Trace Hg detection is of vital importance for environmental monitoring. Herein, we report a novel design of Ru-MOFs modified gold microelectrode for Hg determination. Ru-MOFs are synthesized directly by the cathodic method on gold microelectrode, with the covered area accurately controlled. Cathodic synthesized Ru-MOFs show good conductivity and are suitable to be used as the electrode surface material directly. The synergy of the pre-deposition process and the adsorption process of Ru-MOFs can effectively improves the performance of the sensor. The results show good linearity (R = 0.996) from 0.1 ppb to 5 ppb, with a high sensitivity of 0.583 A ppb mm. The limit of detection is found to be 0.08 ppb and the test process is within 6 min. Most importantly, the senor has a good anti-interference ability and the recoveries are satisfactory. This miniature electrochemical sensor has the potential for on-site detection of trace mercury in the field.

Facile Trace Mercury (II) Sensor Using Statistically Optimized Electrochemical Co-deposited Gold Nanofilm Modified Screen-Printed Carbon Electrodes

Rapid detection of trace mercury (II) in water is very challenging. A novel sensor for the facile detection of mercury (II) was developed using electrochemically co-deposited gold nanofilm modified screen-printed carbon electrodes (EcoD-AuNF/SPCE). Because a monolayer of gold nanofilm is freshly co-deposited during the mercury (II) preconcentration period, no additional modification on an electrode is required prior to a test. Central composite design (CCD) and response surface methodology (RSM) were used to evaluate the effects of the critical testing parameters simultaneously (i.e., the co-deposited gold concentration of $350\,\,\mu \text{g}\,\,\text{L}^{-1}$ , deposition potential of −0.75 V, and testing pH of 3.50). The response of square-wave anodic stripping voltammetry (SWASV) showed a linear relationship with the mercury (II) concentration over a range of 1 to $40~\mu \text{g}$ /L (ppb), with an LoD of $0.29~\mu \text{g}$ /L and sensitivity of $0.37~\mu \text{A}$ /ppb. Significant influences on the mercury (II) stripping peak potential, peak height, and peak shape were observed in the presence of chloride. Therefore, an optimized amount of chloride (i.e., 600 mg/L) was preemptively added to minimize the potential effect of naturally occurring chloride and to improve further the detection sensitivity (i.e., LoD of $0.16~\mu \text{g}$ /L and sensitivity of $0.55~\mu \text{A}$ /ppb). Validation testing using real-world water samples indicated reliable prediction of mercury (II) concentration could be obtained in complex media. In summary, this newly developed voltammetric approach has excellent detection performance and practical significance for potential on-site voltammetric determination of trace mercury (II) in water.

Rapid and accurate automatic temperature calibration of disposable screen-printed heated gold electrodes

Joule-heated electrodes have been used to enhance electrochemical analysis. Due to such direct heating, a steep temperature gradient is created near the electrode surface. The heating device that provides the high-frequency AC (50 kHz or more) has to be calibrated, in order to apply the desired temperature during analysis. The applied temperature of the working electrode influences both its electrical resistance and the electrochemical potential of a redox couple. Open circuit potentiometric (OCP) measurements were performed automatically with screen-printed gold loop electrodes (Au-LE), while applying 50 kHz AC heating pulses of increasing intensity provided by a ThermaLab® AC generator. Potentiometric temperature calibrations were performed using 5 mM equimolar ferri/ferrocyanide in 0.1 M of potassium chloride at 20°C bulk temperature. Potential differences produced during each heat pulse were used to automatically calculate the electrode temperature using the temperature coefficient of this redox couple (−1.6 mV/K). The electrode resistance values at each heating pulse were obtained by measuring the heating voltage and heating current. The automatic temperature calibration experiments with five Au-LEs were shown to be highly reproducible and precise, with an RSD for the temperature of 0.24% and 4% for resistance. The average margin error of OCP temperatures were ± 0.66 K at a 95% confidence level. The temperature coefficient (α) of electrical resistivity of the screen-printed gold layers was found to be 0.0025 °C−1, which is 27% lower than the theoretical value for gold metal. These findings were confirmed by DC resistance measurements using a potentiostat. Comparing the OCP temperature with the resistivity method, the temperature difference was about 0.94 °C (2.8%). Both methods enable quick, reproducible and accurate temperature calibration for disposable Au-LE, which were also used for trace mercury detection in lake water samples.

Improved sensitivity and reproducibility in electrochemical detection of trace mercury (II) by bromide ion & electrochemical oxidation

Nanostructured gold electrodes have been widely used for electrochemical trace analysis of Hg2+ because Hg2+ has superior specificity for the formation of gold amalgam. However, it is still very challenging to achieve both high sensitivity and reproducibility, especially for real environmental water samples due to surface poisoning by organic residues. In this work, we developed two strategies for addressing these challenges. First, we added NaBr (with a final concentration of 0.01 M) to the analytes; this enhanced the sensitivity by two orders of magnitude and improved the reproducibility to be better than RSD <15% because of the synergetic interaction of Br− with Hg2+ and gold at the interface. Second, we developed a pre-oxidation method using a glassy carbon electrode to remove organic residue from the analyte before Hg2+ analysis. The combination of these two approaches results in an efficient, reliable, and fast electrochemical detection technique for on-site trace analysis of Hg2+ that is in concentrations lower than that required by WHO for drinking water.

Facile synthesis of bagasse waste derived carbon dots for trace mercury detection

In this paper, water-soluble nitrogen doped fluorescent carbon dots (N-CDs) have been prepared by a facile hydrothermal treatment of bagasse waste and urea. The prepared N-CDs were characterized by high resolution TEM, fluorescence spectroscopy, FTIR and x-ray photoelectron spectroscopy. The results revealed that the prepared N-CDs were mainly composed of hydroxyl, carboxyl and amino groups with an average size of ca. 5.0 nm. The prepared N-CDs exhibited excellent photoluminescence and emitted light blue fluorescence under a 365 nm UV light. Owing to the selective fluorescent quenching response of Hg2+, the prepared N-CDs have been used as a fluorescent probe for sensitive detection of Hg2+ in water. The fluorescent quenching mechanism could be due to the special coordination interaction between Hg2+ and the surface functional groups of the fluorescent N-CDs. Meanwhile, the fluorescence quenching efficiency decreased linearly with Hg2+ in the concentration range of 0.005–0.8 μM. The detection limit is low to 0.002 μM. The synthesized N-CDs were further applied to the detection of Hg2+ in real water samples.

Organic Material Based Fluorescent Sensor for Hg2+: a Brief Review on Recent Development.

Due to the deleterious effects of mercury on human health and natural ecosystems, high reactivity, non-degradability, extreme volatility and relative water and tissue solubility, it would consider as one of the most toxic environmental pollutants among the transition metals. In the present investigation, we have tried to summarized the several organic material based fluorescent sensor including rhodamine, boron-dipyrromethene (BODIPYs), thiourea, crown-ether, coumarine, squaraines, pyrene, imidazole, triazole, anthracene, dansyl, naphthalenedimide/ naphthalene/ naphthalimide, naphthyridine, iridium (III) complexes, polymeric materials, cyclodextrin, phthalic anhydride, indole, calix [4]arene, chromenone, 1,8-naphthalimides, lysine, styrylindolium, phenothiazine, thiocarbonyl quinacridone, oxadiazole, triphenylamine-triazines, tetraphenylethene, peptidyl and semicarbazone for the trace mercury detection in the aqueous, aqueous-organic and cellular media. The present review provides a brief look over the previous development in the organic material based fluorescent sensor for mercuric ion detection. Furthermore, the ligand-metal binding stoichiometry, binding/association/dissociation constants and the detection limit by the receptors have been particularly highlighted which might be useful for the future design and development of more sensitive and robust fluorescent chemosensor/chemodosimeter for the mercuric ion detection. Graphical Abstract Dummy.

An investigation of preparation, properties, characterization and the mechanism of zinc blende CdTe/CdS core/shell quantum dots for sensitive and selective detection of trace mercury

A convenient, non-enzyme, fluorescent nanosensor was synthesized for the rapid detection of trace mercury.

An electrochemical aptamer biosensor based on "gate-controlled" effect using β-cyclodextrin for ultra-sensitive detection of trace mercury.

A new strategy for construction an electrochemical biosensor for Hg(2+) analysis with extremely high sensitivity was proposed based on "T-Hg(2+)-T" coordination by aptamers and "gate-controlled" amplification by switch of the channels of the probe. SH-β-cyclodextrin was self-assembled on the gold electrode to form an orderly arranged molecularly layer with interspaces among β-CDs; thionine labeled aptamer was then linked on the assembled β-CD. When Hg(2+) was added, the aptamer combined with Hg(2+) and formed "T-Hg(2+)-T" structure, which caused the aptamer folded and the labeled thionine covered the interspaces to block off the channel for probe entrance. The oxidative current of probe decreased, which provide the basis for the determination of Hg(2+). With the gate-controlled amplification, the changes of trace amounts of Hg(2+) will produce great changes of the probe current. The sensor exhibited significantly higher sensitivity with a detection limit of 5.0×10(-15) mol/L, which is lower than other reported methods.

Multiple signal amplified electrochemiluminescent immunoassay for Hg2+ using graphene-coupled quantum dots and gold nanoparticles-labeled horseradish peroxidase.

A multiple signal amplification strategy was designed for an ultrasensitive competitive immunoassay for Hg(2+). This strategy was achieved using graphene conjugated with a large number of CdSe quantum dots to enhance the basal signal and enormous horseradish peroxidase (HRP) labeled with gold nanoparticles (AuNPs) to consume the coreactant H2O2 generated in situ. The immunosensor was constructed by immobilization of coating antigen on poly(diallyldimethylammonium chloride)-graphene-CdSe composites (PDDA-GN-CdSe), and a strong electrochemiluminescence (ECL) signal was obtained. When the immunosensor was immersed in antibody-AuNPs-HRP composites, the ECL signal greatly decreased, which was ascribed to the bound enzyme on the electrode surface. The self-produced coreactant H2O2 was consumed by o-phenylenediamine in the presence of enzyme, effectively decreasing the ECL intensity from the quantum dots. The Hg(2+) in solution and the corresponding coating antigen competed for the limited antibody, and thus, the ECL intensity was linearly dependent on the logarithm of the mercury(II) concentration from 0.2 to 1000 ng mL(-1) with a detection limit of 0.06 ng mL(-1). The immunoassay exhibited good stability and accuracy and acceptable reproducibility, indicating that it provides a promising approach for the detection of trace mercury and other small molecular compounds in environmental samples.

Quantitative detection of trace mercury in environmental media using a three-dimensional electrochemical sensor with an anionic intercalator

Mercury, one of the most widespread highly toxic heavy metals, has severe detrimental effects on human health and the environment. It is significant to develop a sensitive and reliable method of accurately detecting trace levels of mercuric ions in environmental media to meet the ever-increasing demands of ongoing environmental monitoring programs. A three-dimensional mercuric ion sensor was constructed using mercury-specific oligonucleotides, gold nanoclusters, and an anionic intercalator. Due to the steric reaction field in the electrode surface microenvironment formed by the gold nanoclusters, the sensor could spatially capture mercuric ions with electroactive indication to realize trace mercury measurements with high sensitivity; the sensor exhibited strong environmental adaptability, high selectivity, and other advantages. Under optimal conditions, mercuric ions could be detected in the range from 0.05 to 350 nM, and the detection limit was 0.01 nM. The mercuric ion sensor was compared with atomic fluorescence spectrometry to analyze municipal wastewater and river water samples. In addition, the sensor performance was also analyzed according to derived formulae. This accurate method has the potential to be deployed in the field for measurements of mercury in environmental media.

Rhodamine-based fluorescent probe immobilized on mesoporous silica microspheres with perpendicularly aligned mesopore channels for selective detection of trace mercury(ii) in water

A rhodamine-based organic–inorganic hybrid solid fluorescent chemosensor by covalently immobilized R6G derivative on core–shell structured mesoporous silica microspheres with perpendicularly aligned mesopore channels has been prepared. The fluorescent responses of the prepared chemosensor to Hg2+ have been investigated, and the results demonstrated that the proposed hybrid solid fluorescent chemosensor featured a high affinity Hg2+-specific fluorescence response in water by considering the highly dense modification of the rhodamine probe. The detection limit for Hg2+ is 0.1 nM (S/N = 3, which is well below the guideline value given by the World Health Organization) under optimized conditions. Excellent wide linear range (1.0–100.0 nM) and good repeatability (relative standard deviation of 3.2%) were obtained for Hg2+. The proposed chemosensor also exhibited excellent selectivity for Hg2+ over competing environmentally relevant metal ions, and can be used in a wide pH span and regenerated readily. These values, particularly the high sensitivity and excellent selectivity in contrast to the values reported previously in the area of fluorescent Hg2+ detection, demonstrated the analytical performance of the proposed chemosensor could be used for efficient determination of Hg2+ in natural water samples. Toward the purpose of practical application, the proposed chemosensor was further used to determine Hg2+ in real environmental water samples.

Electropolymerized surface ion imprinting films on a gold nanoparticles/single-wall carbon nanotube nanohybrids modified glassy carbon electrode for electrochemical detection of trace mercury(II) in water

Electrochemical detection of Hg(II) using a electropolymerized ion imprinting poly(2-mercaptobenzothiazole) films at the surface of gold nanoparticles/single-walled carbon nanotube nanohybrids modified glassy carbon electrode (PMBT/AuNPs/SWCNTs/GCE) is described for the first time. The Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor exhibits larger binding to functionalized capacity, larger affinity, faster binding kinetics and higher selectivity to template Hg(II). The differential pulse anodic stripping voltammetry (DPASV) response of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor to Hg(II) is ca. 3.7- and 10.5-fold higher than that at the non-imprinted PMBT/AuNPs/SWCNTs/GCE and the imprinted PMBT/AuNPs/GCE, respectively, and the detection limit for Hg(II) is 0.08nM (S/N=3, which is well below the guideline value given by the World Health Organization) and a sensitivity of 0.749μAnM−1 was obtained. Excellent wide linear range (0.4–96.0nM) and good repeatability (relative standard deviation of 2.6%) were obtained for Hg(II). The interference experiments show that Ag(I), Pb(II), Cd(II), Zn(II) and Cu(II) had little or no influence on the Hg(II) signal. These values, particularly the high sensitivity and excellent selectivity in contrast to the values reported previously in the area of electrochemical Hg(II) detection, demonstrate the analytical performance of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE toward Hg(II) is superior to the existing electrodes and could be used for efficient determination of Hg(II) in natural water samples.