Speciation of alkylated metals and metalloids in the environment

Climate Change Implications for Metal and Metalloid Dynamics in Aquatic Ecosystems and its Context within the Decade of Ocean Sciences

Anthropogenic activities are affecting marine ecosystems, notably coastal ones, in multiple ways and at increasing rates, leading to habitat degradation, loss of biodiversity, and greater exposure of flora and fauna to chemical contaminants, with serious effects on ocean health. Chemical pollution, in particular, is a significant negative stressor for aquatic ecosystems, both oceanic and coastal, and has recently been identified as a priority for conservation efforts. Metals and metalloids, in particular, present environmental persistence, bioavailability, tendency to bioaccumulate along the trophic chain, and potential toxic effects. However, the current scenario of climate change is increasingly affecting the aquatic environment, altering water mass flows and the transport of pollutants, aggravating toxic effects and ecological risks. Moreover, although traditional sources of contamination have been studied for decades, many knowledge gaps persist, in addition to the emerging effects of climate change that are still poorly studied. In this regard, this review aims to discuss climate change implications for metal and metalloid dynamics in aquatic ecosystems and its context within the Decade of Ocean Sciences. We also discuss how an increasing interest in plastic pollution has led to contamination by metals and metalloids being neglected, requiring mutual efforts to move forward in the understating of the negative and often lethal impacts of this type of pollutants, thus aiming at prioritizing contamination by metals and metalloids not just in the oceans, but in all water bodies.

Fate and tidal transport of butyltin and mercury compounds in the waters of the tropical Bach Dang Estuary (Haiphong, Vietnam)

In this work, two field campaigns were performed in July 2008 (wet season) and March 2009 (dry season) to produce original data on the concentration, partition and distribution of mercury and butyltin compounds along the tropical Bach Dang Estuary located in North Vietnam (Haiphong, Red River Delta). The results demonstrate that mercury and butyltin speciation in the surface waters of this type of tropical estuary is greatly affected by the drastic changes in the seasonal conditions. During high river discharge in the wet season, there was a large estuarine input of total Hg and tributyltin, while the longer residence time of the waters during the dry season promotes increasing MMHg formation and TBT degradation. Although most of the Hg and TBT is transported into the estuary from upstream sources, tidal cycle measurements demonstrate that this estuary is a significant source of TBT and MMHg during the wet (~3 kg TBT/day) and dry (~3 g MMHg/day) seasons.

In situ arsenic speciation on solid surfaces by desorption electrospray ionization tandem mass spectrometry

A simple and fast (<5 s) method for in situ arsenic speciation on solid surfaces has been developed based on desorption electrospray ionization-tandem mass spectrometry (DESI-MS). Arsenic-polluted environmental samples such as animal feed and plant tissues could be directly monitored by DESI-MS. Each arsenic species in this study, including monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB), arsenocholine (AsC), 4-arsanilic acid (p-ASA), 4-hydroxyphenylarsonic acid (4-OH), Nitarsone, Roxarsone and two inorganic arsenic species, arsenate As(v) and arsenite As(iii), could be detected by their typical m/z and collision induced dissociation (CID) behavior respectively. By the characteristic information, mixtures of different arsenic species could be detected without any sample preparation and separation process. This method could give absolute detection limits of the arsenic species at ng/mm(2) to pg/mm(2) level with a best RSD of 5.3% (n = 5). The method could be potentially applied to in situ environmental monitoring of arsenic pollution, especially that caused by arsenic pesticides, animal feed additives, herbicides and wood treatment.

Methylated Metal(loid) Species in Humans

While the metal(loid)s arsenic, bismuth, and selenium (probably also tellurium) have been shown to be enzymatically methylated in the human body, this has not yet been demonstrated for antimony, cadmium, germanium, indium, lead, mercury, thallium, and tin, although the latter elements can be biomethylated in the environment. Methylated metal(loid)s exhibit increased mobility, thus leading to a more efficient metal(loid) transport within the body and, in particular, opening chances for passing membrane barriers (blood-brain barrier, placental barrier). As a consequence human health may be affected. In this review, relevant data from the literature are compiled, and are discussed with respect to the evaluation of assumed and proven health effects caused by alkylated metal(loid) species.

Parallel on-line detection of a methylbismuth species by hyphenated GC/EI-MS/ICP-MS technique as evidence for bismuth methylation by human hepatic cells

Methylation of metal(loid)s by bacteria or even mammals is a well known process that can lead to increased toxicity for humans. Nevertheless, reliable analytical techniques and tools are indispensable in speciation analysis of trace elements, especially since environmental or biological samples are usually characterised by complex matrices. Here the methylating capability of hepatic cells was observed in vitro. HepG2 cells were incubated with colloidal bismuth subcitrate, bismuth cysteine and bismuth glutathione, respectively for a period of 24 h. For identification the cell lysate was ethylated by sodium tetraethyl borate under neutral conditions. After cryo focussing by purge and trap, the bismuth speciation was carried out via GC/EI-MS/ICP-MS. Colloidal bismuth subcitrate and bismuth cysteine were methylated by HepG2 cells, while no methylated bismuth species was detected after incubation with bismuth glutathione.

Recent advances in mercury speciation analysis with focus on spectrometric methods and enriched stable isotope applications

This paper discusses some recent advances in spectrometric methods and approaches for mercury speciation analysis of environmental samples with focus on isotope dilution techniques for determination of mercury species' concentrations in gaseous samples and reaction rates in soils and sediments. Such analytical data is important inter alia in fundamental research on mercury biogeochemistry and for risk assessments of mercury-contaminated soils and sediments and for designing effective remedial actions. The paper describes how the use of enriched stable isotope tracers in mercury speciation analysis can improve the traceability and accuracy of results, facilitate rational method developments, and be useful for studying biogeochemical processes, i.e. rate of reactions and fluxes, of mercury species. In particular the possibilities to study and correct for unwanted species transformation reactions during sample treatment and to study "natural" transformations of species in environmental samples, or micro- and mesocosm ecosystems, during incubations are highlighted. Important considerations to generate relevant data in isotope tracer experiments as well as reliability and quality assurance of mercury speciation analysis in general are also discussed.

Separation of Hg(II) by foam fractionation in the acidic range: effect of complexation

Foam fractionation is a proven technique for separation of heavy metals. This technique was used for separation of mercury from aqueous solutions. It was found that knowledge of mercury-containing species is essential for this process. A rigorous method is presented for estimating the distribution of free and complex mercury-containing species in aqueous solutions. The chelates of Hg(2+) with ligands such as Cl(-) and OH(-) are quite stable leading to conclude that poor or no separation results when the pH is reduced by HCl or held alkaline. Experimental results indicated that the efficiency of mercury removal closely correlates with pH as well as the concentration of positively charged mercury-containing species. They also indicated that this efficiency is higher at lower Hg concentrations. A removal efficiency of approximately 80% was resulted for solutions containing 2.5x10(-5)M Hg in highly acidic media. It was noticed that this efficiency would drop almost to zero as pH was raised to around 5.5. The theoretical findings were in close agreement with the experimental results.

Arsenic metabolism in multiple myeloma and astrocytoma cells

Arsenic trioxide (As2O3, Trisenox) is used to treat patients with refractory or relapsed acute promyelocytic leukemia (APL). Its ability to induce apoptosis in various malignant cell lines has made it a potential treatment agent for other malignancies and many clinical trials are currently in progress to evaluate its clinical usefulness for multiple myeloma and glioblastoma cancer. In the present study, we investigated the metabolism of As2O3 regarding its cellular biotransformation and interaction with metallothionein (MT) as a possible protective responses of cells to arsenic-induced cytotoxicity. The study was performed on two types of cell treated with As2O3: (1) human astrocytoma (glioblastoma) cell line U87MG treated with 0.6 microM arsenic for 0, 3, 12, 24, and 48 h or 12 microM arsenic for 3, 6, 12, 24, and 48 h and (2) bone marrow cells (BM) from two patients with multiple myeloma (MM) treated with 7 microM arsenic for 0, 43, and 67 h. Cotreatment with vitamin C (1 mg/mL) was tested in longer exposure of MM BM cells. Traces of methylation products (mainly monomethylarsenic acid) were detected in cell lysates of both cell types and in pellets of U87 MG cells, although we found problems with column-sample interactions in cases where methanol pretreatment of the sample was not used. Pentavalent inorganic arsenic (AsV) was identified in both cell types, and up to 80% of total As in MM bone marrow cell lysates was present as AsV. Such an occurrence (generation) of pentavalent arsenic after As2O3 treatment demonstrates the presence of biological oxidation of trivalent arsenic, which could represent an additional protective mechanism of the cell. Vitamin C decreased As cell content and increased the percentage of pentavalent inorganic arsenic (in the growth medium and cells). The presence of metallothionein (MT) and its response to arsenic treatment was checked in all U87 MG cells, in the control, and in one exposed sample of MM BM cells. During 48 h exposure to 0.6 or 12 muM arsenic MTI/II levels increased in U87 MG cells, but with variable Zn levels, increased Cu levels, and As binding observed in traces only. Involvement of the MT-III isoform was negligible. In contrast, 43 h exposure to 7 microMarsenic did not increase MT content in multiple myeloma cells, and the levels even decreased with respect to the control. To evaluate the importance of the observed processes, MTs in U87 and AsIII-AsV conversion in MM BM cells, which could represent a resistance response of cancer cells treated by As2O3, longer-term observation with different arsenic concentrations should be performed.

Inductively coupled plasma mass spectrometry (ICP MS): a versatile tool

Inductively coupled plasma (ICP) mass spectrometry (MS) is routinely used in many diverse research fields such as earth, environmental, life and forensic sciences and in food, material, chemical, semiconductor and nuclear industries. The high ion density and the high temperature in a plasma provide an ideal atomizer and element ionizer for all types of samples and matrices introduced by a variety of specialized devices. Outstanding properties such as high sensitivity (ppt-ppq), relative salt tolerance, compound-independent element response and highest quantitation accuracy lead to the unchallenged performance of ICP MS in efficiently detecting, identifying and reliably quantifying trace elements. The increasing availability of relevant reference compounds and high separation selectivity extend the molecular identification capability of ICP MS hyphenated to species-specific separation techniques. While molecular ion source MS is specialized in determining the structure of unknown molecules, ICP MS is an efficient and highly sensitive tool for target-element orientated discoveries of relevant and unknown compounds. This special-feature, tutorial article presents the principle and advantages of ICP MS, highlighting these using examples from recently published investigations.

Online Standard Additions Calibration of Transient Signals for Inductively Coupled Plasma Mass Spectrometry

An online standard additions calibration method for transient signals in ICPMS is demonstrated in which a small volume of standard is injected as a spike into the sample/carrier stream, overlaying the analyte peak. This technique provides the advantages of conventional standard additions but requires only a single sample run. The method corrects for matrix effects and is suitable for transient signals in which the severity of the matrix effect changes over the analyte peak. The method uses a peak-fitting program to determine the area of the underlying peak and is shown to be effective for the determination of trace metal concentrations in both a high ionic strength matrix and in a biological matrix (urine). Eight analytes with concentrations in the range of 0.82-233.2 mug L-1 in urine were simultaneously determined using a standard spiking solution of 75 mug L-1 injected through a 100-muL loop. The measured concentrations for analytes free of spectral interferences agreed with the certified values, and the precision achieved was comparable to that achieved by the certifying agency. Using a conventional cross-flow nebulizer and Scott-type spray chamber, the accuracy obtained for online standard additions calibration was within 2%, and the precision was within 5%.