Concentration Of Mercury Ions Research Articles

C-phycocyanin from Spirulina maxima as a Green Fluorescent Probe for the Highly Selective Detection of Mercury(II) in Seafood

In this work, a highly selective and sensitive fluorimetric method has been developed for sensing mercury ions in seafood using a fluorescent probe of C-phycocyanin (C-PC) from Spirulina maxima. The interactions between C-PC and mercury ions were systematically characterized by UV-vis spectrophotometer, microscopy imaging, and fluorescence measurements. It was found that the C-PC fluorescence could be quenched by mercury ions triggering the C-PC aggregation phenomenon. Importantly, the fluorescence intensities of C-PC probes could be linearly changed depending on the concentrations of mercury ions, showing the detection limit of 0.0080 μM, and the relative standard deviation of this method was about 1.9%. Moreover, the developed fluorimetry method was successfully applied to detect mercury ions in the real seafood samples (oysters and Pampus argenteus samples), with the acceptable rate of recovery between 93.6 and 107.2%. Such a green, efficient, and cost-effective fluorimetric method of C-PC probe should promise the wide applications for tracing mercury ions levels in seafood.

Mercury Ion Monitoring in Mercury Plating Bath by Anodic Stripping Voltammetry

Anodic stripping voltammetry (ASV) is successfully applied in mM level detection of mercury ion in an electroplating bath which is currently used in preparing a cathodic electrolyzer. Glassy carbon electrode is used for the detection and the optimum condition obtained is 10 s deposition at −1.4 V vs. Ag/AgCl and stripping by scanning from −1.4 to +0.4 V vs Ag/AgCl at 50 mV/s. By applying the method, the mercury ion concentration in the electroplating bath could be successfully monitored during the plating. Keywords: Mercury ion detection, Mercury ion monitoring, Anodic stripping voltammetry, Hg plating bath

Synthesis and characterization of a novel chloromethylated polystyrene-g-2-adenine chelating resin and its application to preconcentrate and detect the concentration of mercury ions in edible mushroom samples

Edible mushrooms are widely usedtoday but the heavy metal pollution of edible mushrooms is not conducive to its industrialization. A novel chloromethylated polystyrene-g-2-adenine chelating resin (AR resin) with simple technology, high adsorption capacity, significant selectivity, and good regenerability was synthesized. Combined with the UV-Vis method, it was applied to mercury preconcentration and determination. The results indicated that the AR resin is essentially free from interferences, which can contribute to accurate determination in waters and foods. Optimization of the resin synthesis was carried out by using response surface methodology. The adsorption properties of the resin for Hg(II) were investigated by batch and column experiments. The statically and dynamic saturated adsorption capacities were 383.4 and 417.0 mg/g. The adsorption kinetic and equilibrium data were well fitted to the second-order model and the Langmuir isotherm model, respectively. Furthermore, the resin and its metal complexes were studied by Fourier transform infrared spectroscopy and thermogravimetric analysis.

Integrating a DNA Strand Displacement Reaction with a Whispering Gallery Mode Sensor for Label-Free Mercury (II) Ion Detection.

Mercury is an extremely toxic chemical pollutant of our environment. It has attracted the world’s attention due to its high mobility and the ease with which it accumulates in organisms. Sensitive devices and methods specific for detecting mercury ions are, hence, in great need. Here, we have integrated a DNA strand displacement reaction with a whispering gallery mode (WGM) sensor for demonstrating the detection of Hg2+ ions. Our approach relies on the displacement of a DNA hairpin structure, which forms after the binding of mercury ions to an aptamer DNA sequence. The strand displacement reaction of the DNA aptamer provides highly specific and quantitative means for determining the mercury ion concentration on a label-free WGM sensor platform. Our approach also shows the possibility for manipulating the kinetics of a strand displacement reaction with specific ionic species.

Radiation‐Synthesized Acrylamide/Crotonic Acid Hydrogels for Selective Mercury (II) Ion Adsorption

AbstractIn this study, swelling and selective mercury adsorption behavior of novel radiation cross‐linked acrylamide/crotonic acid (AAm/CA) copolymers have been investigated in aqueous mercury (II) ion solutions. Swelling experiments were performed in water and in the solution of mercury (II) ions at 25°C, gravimetrically. The equilibrium swelling (S) values of AAm/CA hydrogels were calculated as 11.00 g fluid (g gel)−1 (in mercury (II) ion solution)—35.90 g fluid (g gel)−1 (in water). For sorption of mercury (II) ions onto AAm/CA, hydrogels were studied by batch sorption technique at 25°C. Adsorption kinetics of the hydrogel‐mercury (II) ion system was investigated and some kinetics parameters were calculated. In the experiments of the adsorption, L2‐type (Langmiur type‐2) adsorption in the Giles classification system was found. In addition, the influences of mercury (II) ion concentration, irradiation dose and CA content in hydrogels, temperature of medium, and counter ions in the mercury compounds were investigated. Selectivity test of the hydrogel was made in aqueous solution of other metal ions such as copper (II), lead (II), and cadmium (II) ions. AAm/CA hydrogels‐sorbed mercury (II) ions from the solution of mercury, while the hydrogel did not sorb any heavy metal ions.

Carbon dots serve as an effective probe for the quantitative determination and for intracellular imaging of mercury(II)

We describe a new method for synthesis of water-soluble photoluminescent carbon dots (CDs) by one-pot hydrothermal treatment of adipic acid and triammonium citrate. The CDs have excitation/emission maxima of 340/440 nm, a quantum yield of 0.13, and are shown to be a viable fluorescent probe for the determination of Hg(II). It shows a linear relationship in the 4 to 18 μM mercury ion concentration range. The detection limit is as low as 2.47 μM. The CDs were applied to intracellular sensing and imaging of Hg(II) where they showed low toxicity.

Promoted colorimetric response of spirooxazine derivative: a simple assay for sensitive mercury(II) detection

A spirooxazine derivative 1,3-dihydro-1,3,3-trimethyl-spiro[2-H-indole-2-2′-[2H-1,4] oxazino [2,3-f] [1, 10] phenanthroline] (compound 1) was explored as a sensitive Hg2+ probe. Sensing behavior toward various metal ions including Hg2+, Na+, K+, Ag+, Pb2+, Ni2+, Fe2+, Cu2+, Zn2+, Cd2+, Co2+, Ba2+, Mn2+, Cr3+, Al3+ and Fe3+ was investigated by UV–Vis in acetonitrile solution. Benefiting from the strategy of visual detection, this compound showed preferable selectivity and sensitivity for Hg2+ with a detection limit of 0.68 ppm. In addition, the color of the solution was different, when dropping different concentrations of mercury ions (10−8–10−2 M) into the probe (compound 1). This remarkable color variation (lavender to green) could be observed easily by a naked eye. The approach can not only detect the Hg2+ in acetonitrile solution, but also can detect the Hg2+ in sewage and industrial effluents.

Sensing of bisphenol A and mercury ions in aqueous solutions using a functionalized porous gold electrode

Endocrine disrupting compounds (EDCs) such as bisphenol A (BPA) and mercury ions can accumulate in living tissue, causing many health problems. Therefore, to prevent contaminated water and products reaching consumers, it is necessary to develop a sensitive and efficient sensing system for these compounds. However, common analytical techniques for EDCs are based on mass spectrometry, which is both costly and requires an expert analyst. Herein, we describe the preparation of a functionalized, porous gold electrode for electrochemical sensing of BPA and mercury ions in aqueous solutions that is formed via a templating method and simple pressing. The prepared porous gold electrode was characterized by SEM-EDS, N2 adsorption-desorptions, and FTIR spectroscopy. The prepared porous gold has a very large surface area (8.1 m2/g) and comparable electrical conductivity (1.33 × 104 S/cm) to pure gold. To prevent electrode poisoning by oxidation byproducts of the target analytes, an indirect sensing method was used: the ferricyanide oxidation reaction. For hexyl and thiol-functionalized porous gold electrodes (C6–PAu and SH-PAu), a linear relationship between the current responses and the concentrations of BPA and mercury ions with high correlation coefficients (≥0.9998) at very low aqueous concentrations (≤0.7 μM) was found using differential pulse voltammetry measurements. Also, the C6–PAu electrode could be regenerated easily by washing with ethanol, and was reused five times consecutively.

Extraction of Hg(II) Ions from Aqueous Solution by a Magnetic Nano Sorbent Followed by Determination through Stripping Differential Pulse Voltammetry on Commercial Screen-Printed Kits

Solid phase extraction (SPE) coupled to electrochemical detection on screen-printed carbon electrode (SPCE) has been developed for the quantification of mercury ions in aqueous samples. Mercury ions were extracted using Iron(II,III) oxide magnetic nanoparticles modified with poly(1,8-diaminonaphthalene) [Fe3O4/PDAN] as a sorbent. The adsorbed mercury ions were removed from the polymeric matrix using 1 mL of HCl (0.1 mol L−1) as the eluent. Then, in order to determine the concentration of mercury ion, this solution was analyzed by means of screen printed electrochemical strips. Differential pulse voltammetry (DPV) anodic charge at 0.05 V was selected as the identifying signal and subsequently the influence of experimental parameters affecting the adsorption and desorption steps were investigated and optimized using one-variable-at-a-time methodology as follows: pH of the sample solution, 7.0; amount of the sorbent, 10 mg; adsorption time, 10 min; type of the eluent, HCl; concentration of the eluent, 0.1 mol L−1; volume of the eluent, 1 mL and desorption time, 5 min. Finally, a calibration curve was plotted by the variation of DPV anodic charge as a function of mercury concentration which was linear within the range of 0.1–30.0 ng mL−1. The limit of detection and the limit of quantification were 0.03 (S/N = 3) and 0.1 ng mL−1, respectively.

Mercury–DNA interaction based detection of mercury ions by DNA amplification with high sensitivity and selectivity

An effective and facile approach for mercury detection is essential for environmental protection and human health. In this study, we propose a novel strategy to develop a highly sensitive and selective method for the detection of mercury ions using real-time quantitative polymerase chain reaction (RT-qPCR) technology and the specific binding of Hg2+ in thymine–thymine mismatch complexes. The signal for detection of Hg2+ was generated using RT-qPCR amplification of a template strand of DNA. The sensor exhibited an excellent linear response between the cycle threshold (Ct) and mercury ion concentration in the range of 0.05–100 nM. Under optimised conditions, the detection limit of this method for aqueous Hg2+ was as low as 30 pM. In addition, this system showed good selectivity for Hg2+ over other metal ions. This new approach shows significant potential for detection of Hg2+ in water and other samples.

Selective and “turn-off” fluorimetric detection of mercury(II) based on coumarinyldithiolane and coumarinyldithiane in aqueous solution

In this work, five novel coumarin-based fluorescent probes for mercury ions were developed. The recognition of mercury ions was performed via the mercury(II)-promoted desulfurization of the probes and a reasonable reaction mechanism was proposed and verified by thin layer chromatography (TLC), 1H nuclear magnetic resonance (1H NMR) and fluorescence intensity measurements. All the probes showed excellent optical properties and exclusively distinguish mercury ions from various metal ions in aqueous solutions at pH 7.4. The linear response of the fluorescence emission intensity for all the probes to the concentration of mercury ions was obtained over a wide range of 0.06–1.5μM (0.06–0.9μM for probe 3e). In addition, the biological toxicity and the confocal fluorescence images of probe 3a were also tested on MCF-7 cells.

Rhodamine functionalized magnetic core–shell nanocomposite: An emission “Off–On” sensing system for mercury ion detection and extraction

This paper reported a core–shell structured composite with superparamagnetic ferroferric oxide as the inner core and silica molecular sieve as the outer shell. A rhodamine based sensing dye was covalently grafted into the highly ordered tunnels of silica molecular sieve, so that mercury ion sensing and extraction could be achieved from this composite. This probe loaded core–shell structure was characterized by electron microscopy images, X-ray diffraction patterns, infrared spectra, thermogravimetry and N2 adsorption/desorption measurement. This composite showed increased emission with increasing mercury ion concentration, along with high sensitivity and good selectivity. Linear response and good regenerating performance were also observed from this composite.

Mercury heavy-metal-induced physiochemical changes and genotoxic alterations in water hyacinths [Eichhornia crassipes (Mart.)

Mercury heavy metal pollution has become an important environmental problem worldwide. Accumulation of mercury ions by plants may disrupt many cellular functions and block normal growth and development. To assess mercury heavy metal toxicity, we performed an experiment focusing on the responses of Eichhornia crassipes to mercury-induced oxidative stress. E. crassipes seedlings were exposed to varying concentrations of mercury to investigate the level of mercury ions accumulation, changes in growth patterns, antioxidant defense mechanisms, and DNA damage under hydroponics system. Results showed that plant growth rate was significantly inhibited (52%) at 50mg/L treatment. Accumulation of mercury ion level were 1.99mg/g dry weight, 1.74mg/g dry weight, and 1.39mg/g dry weight in root, leaf, and petiole tissues, respectively. There was a decreasing trend for chlorophyll a, b, and carotenoids with increasing the concentration of mercury ions. Both the ascorbate peroxidase and malondialdehyde contents showed increased trend in leaves and roots up to 30mg/L mercury treatment and slightly decreased at the higher concentrations. There was a positive correlation between heavy metal dose and superoxide dismutase, catalase, and peroxidase antioxidative enzyme activities which could be used as biomarkers to monitor pollution in E. crassipes. Due to heavy metal stress, some of the normal DNA bands were disappeared and additional bands were amplified compared to the control in the random amplified polymorphic DNA (RAPD) profile. Random amplified polymorphic DNA results indicated that genomic template stability was significantly affected by mercury heavy metal treatment. We concluded that DNA changes determined by random amplified polymorphic DNA assay evolved a useful molecular marker for detection of genotoxic effects of mercury heavy metal contamination in plant species.

An ultra-sensitive colorimetric Hg2+-sensing assay based on DNAzyme-modified Au NP aggregation, MNPs and an endonuclease

This paper reports the development of an ultra-sensitive colorimetric method for the detection of trace mercury ions involving DNAzymes, Au nanoparticle aggregation, magnetic nanoparticles and an endonuclease. DNAzyme-sensing elements are conjugated to the surface of Au nanoparticle-2, which can crosslink with the T-rich strands coated on Au nanoparticle-1 to form Au nanoparticle aggregation. Other T-rich stands are immobilized on the surface of MNPs. The specific hybridization of these two T-rich strands depends on the presence of Hg2+, resulting in the formation of a T-Hg2+-T structure. Added endonuclease then digests the hybridized strands, and DNAzyme-modified Au NP aggregation is released, catalysing the conversion of the colourless ABTS into a blue-green product by H2O2-mediated oxidation. The increase in the adsorption spectrum of ABTS+ at 421nm is related to the concentration of Hg2+. This assay was validated by detecting mercury ion concentrations in river water. The colorimetric responses were not significantly altered in the presence of 100-fold excesses of other metal ions such as Zn2+, Pb2+, Cd2+, Mn2+, Ca2+ and Ni2+. The inclusion of both Au NP aggregation and an endonuclease enables the assay to eliminate interference from the magnetic nanoparticles with colorimetric detection, decrease the background and improve the detection sensitivity. The calibration curve of the assay was linear over the range of Hg2+ concentrations from 1 to 30nM, and the detection limit was 0.8nM, which is far lower than the 10nM US EPA limit for drinking water.

Liquid–Solid extraction of mercury (II) from aqueous solution by chelating resin Chelex-100

The sorption of mercury (II) from aqueous medium on a chelating resin Chelex 100 has been studied in batch mode. Since the extraction kinetic was obtained, with a mixture of 0.1 g of resin and 5 mL of mercury (II) at 200. 59 mg/L of initial concentration, extraction equilibrium was reached within 180 min of mixing. The influence of some parameters such as initial mercury (II) ion concentration, initial pH of aqueous solution, ion strength and the amounts of resin have been studied at fixed temperature (20±1 °C). The optimum pH value level for quantitative sorption was 5.7. The best performance obtained was 98.0% of extraction yield equivalent to 14.19 mg /g of resin. The pseudo-first- order equation, pseudo-second-order equation, the intra-particle diffusion model and Boyd’s diffusivity model were used to describe the kinetics data and rate constants were evaluated. The Freundlich and Langmuir adsorption models were applied to describe the equilibrium isotherms.

Method development for the determination of mercury(II) by sequential injection/anodic stripping voltammetry using an in situ gold-film screen-printed carbon electrode

A computer-controlled system, included a sequential injection system and an electrochemical detector, was developed for the determination of mercury(II) ion (Hg2+) concentrations. The screen-printed carbon electrode (SPCE), a well-known low-cost electrode, was modified by overlaying in situ with a gold film (Au-SPCE). Square wave anodic stripping voltammetry (SWASV) using the Au-SPCE was performed with a two-step deposition potential of an initial −0.5V vs Ag/AgCl for the preparation of the gold film and then a deposition potential of +0.2V vs Ag/AgCl for the preconcentration of mercury. An on-line medium exchange method was included in the injection step to reduce the effect of chloride ions, whilst a solid phase extraction cartridge was used to remove interference for copper(II) ions. The flow pattern of the sequentially injected solutions with the synchronized two-step deposition potentials did not significantly affect the detection of Hg2+. Square wave parameters of a 4mV step potential, 150Hz frequency and 30mV amplitude gave an optimal Hg2+ detection sensitivity with a limit of detection of 0.22μgL−1 (sample volume of 0.9mL) without any significant interference effect. This method was successfully applied to determine Hg2+ concentrations in real water samples, including in the chloride-rich samples of sea water and table salt, with very good accuracy (recovery in the range of 96.0–101%).

Mercury removal from aqueous solutions with chitosan-coated magnetite nanoparticles optimized using the box-behnken design.

Nowadays, removal of heavy metals from the environment is an important problem due to their toxicity. In this study, a modified method was used to synthesize chitosan-coated magnetite nanoparticles (CCMN) to be used as a low cost and nontoxic adsorbent. CCMN was then employed to remove Hg(2+) from water solutions. To remove the highest percentage of mercury ions, the Box-Behnken model of response surface methodology (RSM) was applied to simultaneously optimize all parameters affecting the adsorption process. Studied parameters of the process were pH (5-8), initial metal concentration (2-8 mg/L), and the amount of damped adsorbent (0.25-0.75 g). A second-order mathematical model was developed using regression analysis of experimental data obtained from 15 batch runs. The optimal conditions predicted by the model were pH = 5, initial concentration of mercury ions = 6.2 mg/L, and the amount of damped adsorbent = 0.67 g. Confirmatory testing was performed and the maximum percentage of Hg(2+) removed was found to be 99.91%. Kinetic studies of the adsorption process specified the efficiency of the pseudo second-order kinetic model. The adsorption isotherm was well-fitted to both the Langmuir and Freundlich models. CCMN as an excellent adsorbent could remove the mercury ions from water solutions at low and moderate concentrations, which is the usual amount found in environment.

Detection and Spatial Mapping of Mercury Contamination in Water Samples Using a Smart-Phone

Detection of environmental contamination such as trace-level toxic heavy metal ions mostly relies on bulky and costly analytical instruments. However, a considerable global need exists for portable, rapid, specific, sensitive, and cost-effective detection techniques that can be used in resource-limited and field settings. Here we introduce a smart-phone-based hand-held platform that allows the quantification of mercury(II) ions in water samples with parts per billion (ppb) level of sensitivity. For this task, we created an integrated opto-mechanical attachment to the built-in camera module of a smart-phone to digitally quantify mercury concentration using a plasmonic gold nanoparticle (Au NP) and aptamer based colorimetric transmission assay that is implemented in disposable test tubes. With this smart-phone attachment that weighs <40 g, we quantified mercury(II) ion concentration in water samples by using a two-color ratiometric method employing light-emitting diodes (LEDs) at 523 and 625 nm, where a custom-developed smart application was utilized to process each acquired transmission image on the same phone to achieve a limit of detection of ∼3.5 ppb. Using this smart-phone-based detection platform, we generated a mercury contamination map by measuring water samples at over 50 locations in California (USA), taken from city tap water sources, rivers, lakes, and beaches. With its cost-effective design, field-portability, and wireless data connectivity, this sensitive and specific heavy metal detection platform running on cellphones could be rather useful for distributed sensing, tracking, and sharing of water contamination information as a function of both space and time.

Ethylene glycol tetra-acetic acid and salicylic acid improve anti-oxidative ability of maize seedling leaves under heavy-metal and polyethylene glycol 6000-simulated drought stress

Stress caused by divalent heavy metal ions and drought exert many toxic and adverse effects on seedling growth and development of plants, especially on leave growth. Organic acids such as ethylene glycol tetra-acetic acid (EGTA) and salicylic acid (SA) have been shown to alleviate the unfavorable effects exerted by these stresses on seedling growth and metabolism. In order to reveal the physiological mechanism underlying these toxic effects and the alleviated effects exerted by organic acids, maize seedling leaves (genotype “Zhengdan958”) were exposed for 7 days to different concentrations of cadmium (Cd2+), mercury (Hg2+), and lead (Pb2+) ions and to the drought stress-inducing polymer polyethylene glycol (PEG) 6000. The same experiments were also carried out in the presence of EGTA or SA. Treated leaves were analyzed for activities of the anti-oxidative enzymes catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) and for the content of malondialdehyde (MDA). The results showed that stress treatments with the heavy metals Cd2+, Hg2+, and Pb2+ and with PEG all affected the activities of CAT, POD, and SOD, although the extent and patterns of these changes were different under different stress conditions. Both heavy metal and drought stress caused a concentration-dependent increase in MDA content. Treatments in the presence with EGTA or SA showed that both these compounds exerted certain alleviative effects on seedling growth under Cd2+, Hg2+, and Pb2+ stresses and PEG-simulated drought stress, with SA generally showing better effects than EGTA.

Hydrothermal growth of CuO nanoleaf structures, and their mercuric ion detection application.

Mercury is the hazardous heavy metal ion for the environment and the human being therefore its determination is very important and herein we describe the development of mercury ion sensor on the CuO nanoleaf like nanostructures using cetyltrimethylammonium bromide (CTAB) surfactant as template for the growth by hydrothermal growth method. Scanning electron microscopy and X-ray diffraction study has shown high density and good crystal quality of the fabricated CuO nanostructures respectively. The presented mercury ion sensor has detected the wide range of 1.0 x 10(-7) to 1.0 x 10(-1) M mercury ion concentrations with an acceptable Nernstian behaviour and a sensitivity of 30.1 ± 0.6 mV/decade. The proposed mercury ion sensor exhibited low detection limit of 1.0 x 10(-8) M and also a fast response time of less than 5 s. In addition, the presented mercury ion sensor has shown an excellent repeatability, reproducibility, stability and selectivity. Moreover, the mercury ion selective electrode based on CuO nanoleaves was tested as an indicator electrode in the potentiometric titration.