Inorganic Mercury Compounds Research Articles

Online mercury speciation through liquid chromatography with particle beam/electron ionization mass spectrometry detection

The ability of particle beam/electron ionization-mass spectrometry (PB/EI-MS) to provide elemental and molecular information for a sample solution has been evaluated for the speciation of inorganic and organic mercury compounds. Specifically, the EI process yields mass spectra which reflect the chemical species eluting from the chromatographic column, either atomic or molecular. A detailed evaluation of source temperature and electron energy parameters has been performed for the PB/EI-MS method. Preliminary studies demonstrated that the approach can be utilized for the determination of mercury at μg mL−1 levels. A non-linear response at low concentrations (0.1–1 μg mL−1) of mercury was observed due to poor transport of small particles through the PB interface. The use of KCl as a carrier agent to enhance particle transport was investigated. The analyte responses for mercury species showed higher sensitivity with good linearity upon KCl addition, providing limits of detection on the ng mL−1 level (sub-ng absolute). The three mercury species (inorganic, phenyl- and methylmercury) were separated using a reversed phase (C18) column with a total elution time of less than 11 min and the species were detected using PB/EI-MS. Post-column addition of the KCl carrier to the mobile phase was accomplished with a HPLC pump and a tee connection. It is believed that the PB/EI-MS technique is well suited not only for speciation of mercury, but also for obtaining comprehensive speciation information via atomic and molecular mass spectral information of diverse species, and thus can be used to solve a number of speciation challenges.

Comparative Effects of Organic and Inorganic Mercury Compounds on Human Cytokines Production

Comparative Effects of Organic and Inorganic Mercury Compounds on Human Cytokines Production

Solid-phase extraction–gas chromatography–mass spectrometry using a fullerene sorbent for the determination of inorganic mercury(II), methylmercury(I) and ethylmercury(I) in surface waters at sub-ng/ml levels

A novel, straightforward solid-phase extraction system for the determination of inorganic mercury and organomercury compounds in water is proposed. The analytes, in a buffer medium at pH 4.5, are sorbed as diethyldithiocarbamate complexes on a C 60 fullerene column an subsequently eluted and derivatized with sodium tetra- n-propylborate in ethyl acetate. Following elution, 1 μl of extract is injected into a gas chromatograph–mass spectrometer system. The proposed gas chromatography–mass spectrometry speciation method exhibits a linear range of 4–1 ng/ml, and a detection limit of 1.5 ng/l (sample volume, 50 ml). Its repeatibility, as relative standard deviation (RSD) (from 11 standards containing 50 ng/l for each analyte), is ca. 7%. No interferences from metals ions, such as Zn 2+, Fe 3+, Sb 3+, As 3+, Pb 2+, Ni 2+, Cu 2+, Sn 2+, Co 2+, Mn 2+and Cd 2+ were encountered at concentrations 1000 times higher than those of the mercury compounds. The method was used for the speciation of inorganic mercury, methylmercury and ethylmercury in various types of water including sea and waste water.

Renal and hepatic ALA-D activity and selected oxidative stress parameters of rats exposed to inorganic mercury and organoselenium compounds

This paper evaluates the ability of organoselenium compounds [ebselen, selenocystine N-ethyl-carbamate (SeCis), bis-4-isopropyl-2-oxazolinyl phenyl diselenide (AASe)] to prevent HgCl2 toxicity. Rats were injected with HgCl2 (0 or 17 μmol/kg, sc) 6 h after organoselenium compounds had been injected (0 or 50 μmol/kg, sc). In vivo, HgCl2 inhibited renal ALA-D activity (∼48%), increased TBARS level in kidney (∼52%) and reduced the hepatic content of non-protein thiol groups (∼40%), but organoselenium compounds did not prevent such effects. SeCis, per se, increased renal TBARS level (∼42%), while AASe increased hepatic content of ascorbic acid (∼38%). In vitro, renal and hepatic ALA-D activity was inhibited by HgCl2 (⩾25 μm), ebselen (⩾12 μm) and SeCis (⩾4 μm). HgCl2 (400 μm) significantly increased TBARS production in renal and hepatic tissue preparations in vitro, and this effect was completely or partially prevented by organoselenium compounds. Ebselen exhibited thiol peroxidase activity in our assay conditions, while SeCis exhibited thiol-oxidizing properties regardless of the presence of peroxide. AASe had no effect on thiol oxidation. Results suggest that organoselenium compounds could not prevent mercury toxicity in vivo. The protective effect of these compounds against mercury-induced increase of TBARS production in vitro is probably related to an antioxidant action rather than to mercury binding.

Health and environmental impact of mercury: Past and present experience

Mercury exists in various forms including metallic mercury, inorganic and organic mercury compounds. Research studies show that contamination brought about by natural and man-made activities is clearly a growing problem today. In 1956, the first recognized poisoning outbreaks occurred. Minamata Disease is a disorder of the central nervous system caused by the consumption of fish and shellfish contaminated with methylmercury. Clinical manifestation differs from inorganic mercury poisoning in which the kidneys and the renal system are damaged. The toxidrome consists of sensory disorders in the distal portion of the four extremities, cerebral ataxia, bilateral concentric constriction of the visual field, central disorder of ocular movement, central hearing impairment and disequilibrium. Fetal type Minamata Disease bom of mothers being exposed to methylmercury during pregnancy resulted in conditions similar to those associated with infantile cerebral palsywere also documented. Measures to control environmental pollution were implemented such as the environmental restoration project, compensation and relief of victims as part of the health and environmental management undertaken by the government. At present, global research studies are focusing on long-term and low-dose inorganic and methyl mercury exposure; and developmental neurobehavioral toxicity including relevant environmental factors influencing mercury transformations, mass balances and partitioning in ecosystems.

Simultaneous determination of inorganic mercury and methylmercury compounds in natural waters.

The purpose of the present work was to develop a simple, rapid, sensitive and accurate method for the simultaneous determination of inorganic mercury (Hg(2+)) and monomethylmercury compounds (MeHg) in natural water samples at the pg L(-1) level. The method is based on the simultaneous extraction of MeHg and Hg(2+)dithizonates into an organic solvent (toluene) after acidification of about 300 mL of a water sample, followed by back extraction into an aqueous solution of Na(2)S, removal of H(2)S by purging with N(2), subsequent ethylation with sodium tetraethylborate, room temperature precollection on Tenax, isothermal gas chromatographic separation (GC), pyrolysis and cold vapour atomic fluorescence spectrometric detection (CV AFS) of mercury. The limit of detection calculated on the basis of three times the standard deviation of the blank was about 0.006 ng L(-1) for MeHg and 0.06 ng L(-1) for Hg(2+)when 300 mL of water was analysed. The repeatability of the results was about 5% for MeHg and 10% for Hg(2+). Recoveries were 90-110% for both species.

Possibilities of determination of mercury compounds using capillary zone electrophoresis

Capillary zone electrophoresis (CZE) has been used to separate inorganic (Hg 2+) and organic mercury (methyl-, ethyl- and phenylmercury) compounds. In order to achieve the proper CZE separation and UV detection of mercury compounds, their different complexes had to be formed. The advantages of four different complexing agents having thiol group (cysteine, glutathione, 2-mercaptonicotinic acid and mercaptoacetic acid) were studied. In the case of all four agents the optimized electrophoretic separation was achieved in fused silica capillary at 25 kV using 25 mM sodium borate buffer (pH 9.3). Identification and quantification of the mercury species at mg/l levels was carried out by the use of UV spectrophotometric detection at 200, 260 and 300 nm depending on the used complexing agent.

PROLONGATION OF HUMAN NEUTROPHIL SURVIVAL BY LOW-LEVEL MERCURY VIA INHIBITION OF SPONTANEOUS APOPTOSIS

Low levels of organic and inorganic mercury compounds have been reported previously to induce cell death by apoptosis in human peripheral blood mononuclear cells (MNC), but little is known about their potential effects on the viability and death of polymorphonuclear neutrophils (PMN). In contrast to MNC, PMN are known to undergo readily spontaneous apoptosis both in vivo and in vitro. Therefore, it was hypothesized that PMN may differ from MNC in their reactions to low mercury levels. The effects of methylmercuric chloride (MeHgCl) and mercuric chloride (HgCl 2 ) were evaluated in concentration- response and time-course studies on human PMN viability and on their modes of cell death after in vitro incubation at 37°C. Cell death by apoptosis or necrosis was assessed by annexin V-fluorescein isothiocyanate binding to externalized phosphatidylserine in conjunction with propidium iodide, and flow cytometry analysis. Morphologic counting of pyknotic nuclei and the fluorescence properties of the DNA-binding dye Hoechst 33342 in combination with propidium iodide were used to further confirm apoptotic cell death and to characterize the sequence of Hg-induced cell death. Results show that low concentrations of MeHgCl (1-7.5 µ M ) that were cytotoxic to MNC actually inhibited PMN spontaneous apoptosis. Low-level HgCl 2 reproduced the anti-apoptotic effects of MeHgCl on PMN, but to a lower extent. Higher concentrations of MeHgCl and HgCl 2 were necro-genic to PMN, but MeHgCl was about an order of magnitude more toxic, and discrete differences were observed in the modalities of cell death induced by both species. These data reveal for the first time that (1) low levels of organic and inorganic mercury species protect human PMN from cell death via inhibition of spontaneous apoptosis, and (2) PMN are more resistant than MNC to mercury-induced cytotoxicity. Since delayed apoptosis and increased resistance to toxicant-induced cell death may lead to excessive accumulation of senescent PMN, evidence indicates that findings of this study may have implications for mercury-induced autoimmunity and inflammation.

Capillary electrophoretic determination of mercury compounds in different matrixes

Capillary electrophoresis has been used to separate inorganic (Hg2+) and organic (methyl-, ethyl-, and phenylmercury) mercury compounds as their cysteine complexes. The optimized electrophoretic separation was performed in fused-silica capillary tubing at 25 kV with 25mm sodium borate buffer (pH 9.3). Identification and quantification of the mercury species at mg L−1 levels was achieved by use of UV detection at 200 nm. The relative standard deviation (n=10) ranged from 0.38 to 0.51% for migration times and from 0.43 to 2.94% for corrected peak areas. Good recovery (>90%) was obtained for all four mercury species in surface waters, and for inorganic mercury and methylmercury in five- to tenfold diluted biofluids (urine, saliva, and cerebrospinal fluid). TheLOQ values obtained were too high to be useful for determination of mercury species in real samples.

Preconcentration speciation method for mercury compounds in water samples using solid phase extraction followed by reversed phase high performance liquid chromatography

A simple and rapid method for in situ preconcentration of inorganic and organic mercury compounds in water samples, based on solid phase extraction using dithizone immobilised on a reversed-phase C18 cartridge, has been developed. The adsorbed complexes were stable on the cartridge for at least 2 weeks. The speciation analysis of methylmercury (MeHg), phenylmercury (PhHg) and inorganic mercury (Hg (II)) were done by reversed-phase high performance liquid chromatography. The calibration graphs of MeHg, PhHg and Hg (II) were linear ( r>0.999) from the detection limits (0.58, 0.66 and 0.54 ng) to 38, 25 and 26 ng of Hg, respectively. The average recoveries of MeHg, PhHg and Hg (II) from spiked samples (0.3–48.0 μg l −1 Hg) were 98±3, 99±1 and 100±7%, respectively. By applying SPE procedure a 200-fold concentration of the sample was obtained.

Bacterial resistance to disinfectants: present knowledge and future problems

Bacterial resistance to antibiotics is a long-established, widely-studied problem. Increasingly, attention is being directed to the responses of various types of microbes to biocides (antiseptics, disinfectants and preservatives). Different groups of bacteria vary in their susceptibility to biocides, with bacterial spores being the most resistant, followed by mycobacteria, then Gramnegative organisms, with cocci generally being the most sensitive. There are wide divergencies within this general classification. Thus, (i) spores of Bacillus subtilis are less susceptible to biocides than those of Clostridium difficile: (ii) Mycobacterium chelonae strains may show high resistance to glutaraldehyde and M. avium intracellulare is generally less sensitive than M. tuberculosis; (iii) Gram-negative bacteria such as Pseudomonas aeruginosa, Providencia spp and Proteus spp may be difficult to inactivate; (iv) enterococci are less sensitive than staphylococci to biocides and antibioticresistant strains of Staphylococcus aureus might show low-level biocide resistance. The mechanisms involved in biocide resistance to biocides are becoming better understood. Intrinsic resistance (intrinsic insusceptibility) is found with bacterial spores, mycobacteria and Gram-negative bacteria. This resistance might, in some instances, be associated with constitutive degradative enzymes but in reality is more closely linked to cellular impermeability. The coats(s) and, to some extent, the cortex in spores, the arabinogalactan and possibly other components of the mycobacterial cell wall and the outer membrane of Gram-negative bacteria limit the concentration of active biocide that can reach the target site(s) in these bacterial cells. A special situation is found with bacteria present in biofilms, which can be considered as being an intrinsic resistance mechanism resulting from physiological (phenotypic) adaptation of cells. Acquired resistance to biocides may arise by cellular mutation or by the acquisition of genetic elements. Plasmid/transposon-mediated resistance to inorganic and organic mercury compounds by hydrolases and reductases has been extensively studied. Plasmid-mediated resistance to some other biocides in Gram-negative bacteria and in staphylococci has been described, but its significance remains uncertain. As to the future, there is a need to establish conclusively whether there is a clear-cut linkage between antibiotic and biocide resistance in non-sporulating bacteria and whether biocides can select for antibiotic resistance. Additionally, the responses to biocides of new and emerging pathogens must be assessed. At the same time, continuing research is necessary to establish further the underlying mechanisms of resistance and to provide more efficient means of bacterial inactivation.

Application of Isotope Dilution to Ion Trap Gas Chromatography/Mass Spectrometry

Isotope dilution has been applied to an approach recently developed to quantify inorganic mercury compounds by ion trap gas chromatography/mass spectrometry (GC/MS). In this approach, a chemical al...

Development of a technique for the analysis of inorganic mercury salts in soils by gas chromatography/mass spectrometry

A technique has been developed to analyze environmentally relevant samples for organic and inorganic mercury compounds. A solid phase microextraction (SPME) fiber was used as a sampling medium in both water and water/soil slurries. Quantification of inorganic mercury was accomplished through a chemical alkylation reaction designed to convert an inorganic mercury salt to an organomercury compound prior to GC/MS analysis; this was found to be the rate limiting step in the analysis. Two alkylating reagents were investigated: methylpentacyanocobaltate (III) (K 3[Co(CN) 5CH 3]) and methylbis(dimethylglyoximato)pyridinecobalt (III) (CH 3Co(dmgH) 2Py). Methylbis(dimethylglyoximato)pyridinecobalt (III) was found to be superior for this application because it produced a single reaction product, methylmercury iodide, with an efficiency of ∼95%. Detection limits were ∼7 ppb in water and ∼2 ppm in soil. The poorer results in soil were due to an increase in background signal (∼10 times compared to water) and a reduction in analyte signal (as much as 100 times). This reduction in signal intensity is believed to be caused by complex soil chemistry. Manipulation of the solution chemistry [e.g. oxidation of mercury (0) → mercury (II)], before or during the alkylation step, may improve the detection limits and increase the number of elements amenable to analysis. Keywords: Gas chromatography/mass spectrometry; Inorganic analysis; Elemental; Mercury compounds; Chemical alkylation

Determination of inorganic and organic mercury compounds by capillary gas chromatography coupled with atomic absorption spectrometry after preconcentration on dithizone-anchored poly(ethylene glycol dimethacrylate-hydroxyethylmethacrylate) microbeads

Poly(EGDMA-HEMA) microbeads were prepared by suspension polymerization of ethylene glycol dimethacrylate (EGDMA) and hydroxyethyl methacrylate (HEMA). Poly(vinyl alcohol), benzoyl peroxide and toluene were used as stabilizer, initiator, and diluent, respectively. A chelating ligand, dithizone, was then attached. The microbeads were characterized by FTIR spectrometers and elemental analysis. The affinity microbeads containing 118.9 μmol dithizone g −1 polymer were used for the adsorption/desorption of inorganic mercury [Hg], methyl mercury chloride [CH 3HgCl] and ethyl mercury chloride [C 2H 5HgCl] from aqueous media at concentrations in the range 5–1000 μg l −1 and various pH values (2.0–8.0). Adsorption rates were high, and adsorption equilibria were reached in about 30 min. The maximum adsorption of mercury species onto the dithizone-anchored microbeads from their individual solutions was 138 mg g −1 for Hg(II), 221 mg g −1 for CH 3HgCl and 207 mg g −1 for C 2H 5HgCl. The same behavior was observed during competitive adsorption in the case of the adsorption from their mixture. The affinity order of mercury species was CH 3HgCl > C 2H 5HgCl > Hg(II). Dithizone-anchored microbeads are suitable for repeated use for more than 5 cycles without noticeable loss of adsorption capacity. Speciation of organomercurials was performed using a Gas chromatography-atomic absorption spectrometry coupled system. Detection limits were increased at least 120-fold with this preconcentration approach using the dithizone-anchored microbeads.

Thimerosal positivities: the rôle of SH groups and divalent ions

For a better understanding of the mechanistic details of the interactions of organomercury compounds inside the skin, 32 subjects who previously had given positive patch-test reactions to thimerosal (TH) and negative reactions to thiosalicylic acid, were divided into 2 groups. 16 subjects were repatch tested to ethylmercury chloride (EtHgCl) and to solutions containing EtHgCl mixed with L-cysteine and glutathione, respectively. The remaining 16 were repatch tested to EtHgCl and to solutions containing EtHgCl mixed with chlorides of Zn, Mg, and Mn, respectively. The results showed that whilst L-cysteine, glutathione and ZnCl2 were able to abolish or to reduce the positive reactions to EtHgCl, chlorides of Mg and Mn were unable to do so. Patch tests revealed that in causing positive reactions to TH, EtHg probably interacted with thiol groups and with Zn ions, as in biological systems when causing toxic effects. The limited number of TH reactions in the general population, the constant presence of concomitant positive reactions to EtHgCl and MeHgCl, and the lack of cross-reactivity with other organic or inorganic mercury compounds, lead us to speculate that reactions to TH are due to organomercury alkyl compounds, and that positive subjects have a constitutively reduced capability to metabolize organomercury compounds, rather than to reveal previous exposure.

Application of a teflon™ dynamic flux chamber for quantifying soil mercury flux: Tests and results over background soil

High precision and low blank contamination were achieved with a Teflon™ dynamic chamber for measuring, soil mercury flux. Using this chamber, background soil mercury flux averaged between 2 and 7 ng m −2 h −1 over forest soil, and between 12 and 45 ng m −2 h −1 over open field soil. Spatial heterogeneity of soil mercury flux at duplicate plots co-located within 2 m was small but significant, differing by 20–50%. Elevated mercury emission over field soil occurred in the presence of direct sunlight at the open field sites. Solar radiation, soil temperature and soil moisture were all significant factors effecting mercury emission from soil. Solar radiation affected the reduction of naturally occurring, inorganic soil mercury compounds to volatile elemental mercury (Hg°). We estimate that background soil accounts for the gross emission of ∼ 109 g yr −1 of Hg° to the atmosphere, with approximately two-thirds of this total from sunlight-exposed soil and the remainder from forest and other shaded-soil ecosystems.

Solid-phase microextraction combined with electrochemistry

Solid-phase microextraction combined with electrochemistry (SPME/EC) for trace level mercury determination is reported. An SPME/EC fibre was made of a carbon steel wire with a 10 µm gold coating. Mercury(II) ions were electrochemically extracted from aqueous solution, and desorbed with a dedicated desorption system, then detected by ion-trap GC–MS. Mercury(II) ions in aqueous solution, and mercury vapour in gas, were detected. Inorganic mercury and organomercury compounds were differentiated.

Voltammetric quantification and speciation of mercury compounds

Abstract The use of a carbon paste electrode modified with a thiolic resin for the determination of inorganic mercury and organomercury compounds, present simultaneously in a sample, is described. The compounds are first preconcentrated at the electrode surface by means of a purely chemical reaction with the modifier on the electrode surface. The high affinity of the modifier for the mercury compounds ensures low limits of detection and determination. Differentiation between several mercury species is possible by control of the reduction potential applied to the working electrode. This selective reduction results in the formation of atomic mercury at the electrode surface which can be determined with a very high sensitivity by means of its re-oxidation wave in cyclic voltammetry. Optimization of the instrumental parameters and evidence for the reduction processes are discussed. Analysis of inorganic mercury in the presence of methylmercury, with a detection limit of 4 μg Hg 1 −1 , and of methylmercury in the presence of inorganic mercury, with a detection limit of 2 μg Hg 1 −1 , is described in detail. In both cases the preconcentration time is 6 min. Other organomercury species can also be quantified. Application of the method to environmental aquatic samples is discussed.

ChemInform Abstract: Critical Review of Analytical Methods for Determination of Inorganic Mercury and Methylmercury Compounds

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Preliminary appraisal of a novel sampling and storage technique for the speciation analysis of lead and mercury in seawater

A sampling technique suitable for the preconcentration of lead and mercury species from seawater was developed and evaluated in this preliminary study. Seawater was first pumped through a tubular functional membrane at a flow rate of 2 ml min−1 for adjustment of the sample pH. The analyte species were then enriched by solid-phase extraction in a microcolumn containing a resin with immobilized dithiocarbamate (DTC) groups. Optimum recoveries of alkyl- and inorganic lead species were obtained at a pH of about 7, whereas the enrichment efficiencies of alkyl- and inorganic mercury compounds were fairly independent of pH. The buffering membrane was effective in adjusting the pH of the seawater stream from its natural value of 8.1 to 7.1 prior to analyte enrichment on the DTC resin. Storage stability of the analyte species on the column was also studied, but found to be poor, indicating that elution from the DTC resin and further sample processing should commence as soon as possible after loading. Suggestions for further development and improvement of the proposed sampling technique are given.