Separation Of Mercury Species Research Articles

Assessment of mercury pollution sources in beach sand and coastal soil by speciation analysis

BackgroundAn essential requisite for controlling and monitoring mercury in the environment is to identify its species in different types of soils and sediments, as this will help not only to establish its mobility in the environment and ecosystem and the degree of its toxicity, but also to establish the source of contamination. The objective of this work was to identify the origin of mercury in beach sands and soil taken from a coastal region with previously high mining and industrial activity by characterizing the mercury species using the technique known as thermal desorption (HgTPD).ResultsApart from quartz, the main mineral species identified in the raw sands and soil were calcite, fluorite and barite. The concentration of mercury ranges from 5 to 23 µg g−1, and although it is distributed in different proportions in the function of the size, thermal desorption profiles demonstrated that the mercury species present in the samples do not vary with the mercury concentration and the particle size. By means of HgTPD, mercury oxide (HgO) was identified in the beach sands, whereas mercury sulfide (HgS) was found in the soil sample taken from the vicinity of the beach. Complementary methodologies foster the HgTPD conclusions and verify that mercury is present mostly in insoluble stable (HgS) or low-mobility (HgO) forms in the samples studied. Analyses by ICP-MS after sequential extraction and HPLC separation of mercury species show that inorganic mercury is the predominant form in the samples.ConclusionsThe technique HgTPD is a very useful tool to ascertain the origin of mercury in contaminated beach sands and shoreline soils. In the particular area studied in this work, the species identified indicate that previous mining activity was the source of the mercury and rule out the possibility that contamination is derived from coal combustion activities ongoing in the region.

Comparison of direct mercury analyzer and FIA-CV-AAS in determination of methylmercury in fish

Methylmercury (MeHg) has been determined in fish reference materials by direct mercury analyzer (DMA 80) and FIA-CV-AAS. In order to evaluate accuracy, certified reference materials (Fish protein, NRCC - Dorm 4 and fish material, Ipen - Dourada 1) were analyzed after extraction and separation of mercury species. Good agreement of the results have been obtained (relative error of the determination between the methods varied from 1.5% to 39%). The repeatability of the results varied from 4% to 26%.

Mercury speciation in Cuban commercial edible fish by HPLC-ICP-MS using the double spike isotope dilution analysis strategy

A sensitive and accurate quantitative method for the speciation of inorganic Hg2+ and methyl-mercury by ID-HPLC–ICP-MS has been optimised and implemented for marine fish samples. Quantitative extraction of Hg species was achieved using a 0.1% (v/v) 2-mercaptoethanol, 0.05% (w/v) L-cysteine and 0.10% (v/v) HCl solution by sonication for 30 min. Chromatographic separation of mercury species was carried out on a C8 reverse phase column with 0.05% (v/v) 2-mercaptoethanol, 0.075% (w/v) L-cysteine and 0.06 mol L−1 ammonium acetate as the mobile phase. A species specific isotope dilution analysis approach, using 201CH3Hg+ and 200Hg2+ was employed for the quantification of both species. Two biological Certified Reference Materials (DOLT-2, DORM-2) were analysed to assess the analytical performance. No significant differences were found between the obtained concentrations and the certified reference values for total Hg and CH3Hg+. The results indicate that no species interconversion reactions occurred during the used extraction and chromatographic separation procedures. The detection limits for CH3Hg+ and Hg2+ species were 7.7 and 5.2 ng g−1, respectively. The method recovery (expressed as the sum of both species contents in relation to total Hg concentration analysed by ICP-MS) was about 97 ± 5%. The procedure was applied to speciation of mercury in 12 species of the most commonly consumed commercial fish in Cuba.

Assessment of Modified Matrix Solid-Phase Dispersion as Sample Preparation for the Determination of CH3Hg+ and Hg2+ in Fish

This paper reports, for the first time, the development of an analytical method employing modified matrix solid-phase dispersion (MSPD) for the extraction of CH3Hg(+) and Hg(2+) species from fish samples. Separation and determination of mercury species were performed by gas chromatography coupled to mass spectrometry (GC/MS). Important MSPD parameters, such as sample mass, type and mass of solid support, concentration of extraction solution (HCl and NaCl), and stirring time, were investigated by the response surface methodology. The derivatization step and the separation of mercury species were also evaluated for the determination by GC/MS. Quantitative recoveries were obtained with 0.2 g of fish sample, 0.5 g of SiO2 as the solid support, 0.5 mol L(-1) NaCl and 4.2 mol L(-1) HCl as the extraction solution, and 1 min stirring time. The MSPD method showed to be suitable for the extraction and determination of mercury species in certified reference materials of dogfish liver (DOLT-3) and dogfish muscle (DORM-2). It had good agreement (about 99%) with the certified values, and the relative standard deviation was lower than 9.5%. The limits of detection were 0.06 and 0.12 μg g(-1), for CH3Hg(+) and Hg(2+), respectively. A matrix effect was observed, and the quantification was carried out by the matrix-matched calibration. The method was applied to tuna fish ( Thunnus thynnus ), angel shark ( Squatina squatina ), and guitarfish ( Rhinobatos percellens ) samples. The results of the mercury speciation by MPSD and GC/MS were compared to the total mercury concentration determined by flow injection cold vapor generation inductively coupled plasma mass spectrometry, after microwave-assisted digestion. Agreement ranged from 102% to 105%.

A simple method for methylmercury, inorganic mercury and ethylmercury determination in plasma samples by high performance liquid chromatography–cold-vapor-inductively coupled plasma mass spectrometry

A simple and sensitive method with a fast sample preparation procedure is proposed for the determination of mercury species in plasma/serum. The method combines online high-performance liquid chromatography separation, Hg cold-vapor formation and inductively coupled plasma mass spectrometry detection. Prior to analysis, plasma (250μL) was accurately pipetted into 15mL conical tubes. Then, an extractant solution containing mercaptoethanol, L-cysteine and HCl was added to the samples following sonication for 10min. Quantitative mercury extraction was achieved with the proposed procedure. Separation of mercury species was accomplished in less than 8min on a C8 reverse phase column with a mobile phase containing 3% v/v methanol+97% v/v (0.5% v/v 2-mercaptoethanol+0.05% v/v formic acid). The method detection limits were found to be 12ngL−1, 5ngL−1 and 4ngL−1 for inorganic mercury, ethylmercury and methylmercury, respectively. Method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from NIST. Additional validation was provided by the analysis of a secondary reference serum sample from the INSQ-Canada. Finally, the method was successfully applied for the speciation of mercury in plasma samples collected from volunteers exposed to methylmercury through fish consumption. For the first time to our knowledge, levels of different species of Hg in plasma samples from riverside populations exposed to MeHg were determined.

Applicability of multisyringe chromatography coupled to cold-vapor atomic fluorescence spectrometry for mercury speciation analysis

In this paper, a novel automatic approach for the speciation of inorganic mercury (Hg 2+), methylmercury (MeHg +) and ethylmercury (EtHg +) using multisyringe chromatography (MSC) coupled to cold-vapor atomic fluorescence spectrometry (CV/AFS) was developed. For the first time, the separation of mercury species was accomplished on a RP C18 monolithic column using a multi-isocratic elution program. The elution protocol involved the use of 0.005% 2-mercapthoethanol in 240 mM ammonium acetate (pH 6)–acetonitrile (99:1, v/v), followed by 0.005% 2-mercapthoethanol in 240 mM ammonium acetate (pH 6)–acetonitrile (90:10, v/v). The eluted mercury species were then oxidized under post-column UV radiation and reduced using tin(II) chloride in an acidic medium. Subsequently, the generated mercury metal were separated from the reaction mixture and further atomized in the flame atomizer and detected by AFS. Under the optimized experimental conditions, the limits of detection (3 σ) were found to be 0.03, 0.11 and 0.09 μg L −1 for MeHg +, Hg 2+ and EtHg +, respectively. The relative standard deviation (RSD, n = 6) of the peak height for 3, 6 and 3 μg L −1 of MeHg +, Hg 2+ and EtHg + (as Hg) ranged from 2.4 to 4.0%. Compared with the conventional HPLC–CV/AFS hyphenated systems, the proposed MSC–CV/AFS system permitted a higher sampling frequency and low instrumental and operational costs. The developed method was validated by the determination of a certified reference material DORM-2 (dogfish muscle), and was further applied for the determination of mercury species environmental and biological samples.

Mercury speciation in seafood samples by LC–ICP-MS with a rapid ultrasound-assisted extraction procedure: Application to the determination of mercury in Brazilian seafood samples

This paper describes a simple method for mercury speciation in seafood samples by LC–ICP-MS with a fast sample preparation procedure. Prior to analysis, mercury species were extracted from food samples with a solution containing mercaptoethanol, l-cysteine and HCl and sonication for 15min. Separation of mercury species was accomplished in less than 5min on a C8 reverse phase column with a mobile phase containing 0.05%-v/v mercaptoethanol, 0.4%m/v l-cysteine and 0.06molL−1 ammonium acetate. The method detection limits were found to be 0.25, 0.20 and 0.1ngg−1 for inorganic mercury, ethylmercury and methylmercury, respectively. Method accuracy is traceable to Certified Reference Materials (DOLT-3 and DORM-3) from the National Research Council Canada (NRCC). With the proposed method there is a considerable reduction of the time of sample preparation. Finally, the method was applied for the speciation of mercury in seafood samples purchased from the Brazilian market.

Methylmercury and inorganic mercury determination in blood by using liquid chromatography with inductively coupled plasma mass spectrometry and a fast sample preparation procedure

Despite the necessity to differentiate chemical species of mercury in clinical specimens, there are a limited number of methods for this purpose. Then, this paper describes a simple method for the determination of methylmercury and inorganic mercury in blood by using liquid chromatography with inductively coupled mass spectrometry (LC–ICP-MS) and a fast sample preparation procedure. Prior to analysis, blood (250 μL) is accurately weighed into 15-mL conical tubes. Then, an extractant solution containing mercaptoethanol, l-cysteine and HCl was added to the samples following sonication for 15 min. Quantitative mercury extraction was achieved with the proposed procedure. Separation of mercury species was accomplished in less than 5 min on a C18 reverse-phase column with a mobile phase containing 0.05% (v/v) mercaptoethanol, 0.4% (m/v) l-cysteine, 0.06 mol L −1 ammonium acetate and 5% (v/v) methanol. The method detection limits were found to be 0.25 μg L −1 and 0.1 μg L −1 for inorganic mercury and methylmercury, respectively. Method accuracy is traceable to Standard Reference Material (SRM) 966 Toxic Metals in Bovine Blood from the National Institute of Standards and Technology (NIST). The proposed method was also applied to the speciation of mercury in blood samples collected from fish-eating communities and from rats exposed to thimerosal. With the proposed method there is a considerable reduction of the time of sample preparation prior to speciation of Hg by LC–ICP-MS. Finally, after the application of the proposed method, we demonstrated an interesting in vivo ethylmercury conversion to inorganic mercury.

Mercury speciation in sea food by flow injection cold vapor atomic absorption spectrometry using selective solid phase extraction

An on-line inorganic and organomercury species separation, preconcentration and determination system consisting of cold vapor atomic absorption spectrometry (CV-AAS or CV-ETAAS) coupled to a flow injection (FI) method was studied. The inorganic mercury species was retained on a column (i.d., 3 mm; length 3 cm) packed to a height of 0.7 cm with a chelating resin aminopropyl-controlled pore glass (550 Å) functionalized with [1,5-bis (2 pyridyl)-3-sulphophenyl methylene thiocarbonohydrazyde] placed in the injection valve of a simple flow manifold. Methylmercury is not directly determined. Previous oxidation of the organomercurial species permitted the determination of total mercury. The separation of mercury species was obtained by the selective retention of inorganic mercury on the chelating resin. The difference between total and inorganic mercury determined the organomercury content in the sample. The inorganic mercury was removed on-line from the microcolumn with 6% (m/v) thiourea. The mercury cold vapor generation was performed on-line with 0.2% (m/v) sodium tethrahydroborate and 0.05% (m/v) sodium hydroxide as reducing solution. The determination was performed using CV-AAS and CV-ETAAS, both approaches have been used and compared for the speciation of mercury in sea food. A detection limit of 10 and 6 ng l −1 was achieved for CV-AAS and CV-ETAAS, respectively. The precision for 10 replicate determinations at the 1 μg l −1 Hg level was 3.5% relative standard deviation (R.S.D.), calculated from the peak heights obtained. Both approaches were validated with the use of two certified reference materials and by spiking experiments. By analyzing the two biological certified materials, it was evident that the difference between the total mercury and inorganic mercury corresponds to methylmercury. The concentrations obtained by both techniques were in agreement with the certified values or with differences of the certified values for total Hg 2+ and CH 3Hg +, according to the t-test for a 95% confidence level. It is amazing how this very simple method is able to provide very important information on mercury speciation.

Ion exchange preconcentration and separation of mercury species by CE with indirect contactless conductometric detection

Capillary electrophoretic separation of four mercury species (inorganic Hg(2+), methyl-, ethyl-, and phenylmercury) was achieved in less than 8 min with an electrolyte consisting of 150 mM 2-amino-2-methyl-propanol (AMP) at pH 11.6. The analytes were complexed with 0.1% mercaptopropionic acid (MPA), separated in counter-EOF as anionic complexes, and detected by a contactless conductometric detector. Ion exchange preconcentration with on-column formation of MPA-mercury complexes was developed. Preconcentration factors of 25-150 were achieved and LODs in the range of 2.9-6.9 ng/mL were feasible. This method may prove to be applicable as a rapid screening method for mercury speciation in environmental samples.

Separation and preconcentration of inorganic and organomercury species in water samples using a selective reagent and an anion exchange resin and determination by flow injection-cold vapor atomic absorption spectrometry

An on-line inorganic (InHg) and organomercury (OrHg) species separation, preconcentration and determination system consisting of cold vapor atomic absorption spectrometry (CV-AAS) coupled to a flow injection (FI) method was studied. The inorganic mercury species was retained on a column (id, 3 mm; length, 80 mm) charged with a Dowex 1X-8 resin (particle size 50–100 mesh) as the anionic complex formed with Methylthymol Blue (MTB), at pH 6.3. Previous oxidation of the organomercurial species permitted the determination of total mercury. Therefore, the separation of mercury species was obtained with the combined use of on-line selective formation of the InHg–MTB complex and the retention of this anionic compound on the anion exchange resin. The difference between total and inorganic mercury determined the organomercury content in the samples. The inorganic mercury was removed on-line from the micro-column with 3 M nitric acid. The mercury cold vapor generation was performed in an on-line system with 7.0% (w/v) SnCl2 and 20% (v/v) HCl as reducing solution. A preconcentration factor of 180 was obtained for the preconcentration of 250 ml of aqueous solution. The detection limit for InHg and OrHg was 0.8 ng l−1. The precision for ten replicate determinations at the 15 ng l−1 Hg level was 4.4% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the separation and preconcentration system for mercury species was linear, with a correlation coefficient of 0.9994 at levels near the detection limit up to at least 100 µg l−1. The accuracy of the method was evaluated by the analysis of a certified reference material QC Metal LL3 Mercury in Water. The method was successfully applied to the speciation of mercury in water samples.

Gas chromatography coupled with atomic absorption spectrometry — a sensitive instrumentation for mercury speciation

New instrumentation for the speciation of mercury is described, and is applied to the analysis of natural water samples. The separation of mercury species is effected using gas chromatography of derivatized mercury species on a widebore capillary column. The solvent is vented using a bypass valve and the separated mercury species are pyrolysed on-line at 800°C for production of mercury atoms. These are then detected by atomic absorption spectrometry (AAS) at the 253.7 and 184.9 nm lines simultaneously in a quartz cuvette. The use of the 184.9 nm line provides a more than five-fold increase in sensitivity compared with the conventional 253.7 nm line and an absolute detection limit of 0.5 pg of mercury. The dynamic range of the combined analytical lines provides a linear response over more than three orders of magnitude. A number of organic compounds not containing mercury are also detected following pyrolysis, especially at the 184.9 nm line. These background species must not co-elute at the retention times for methyl- and inorganic mercury, as otherwise a positive interference would result. By maximizing the chromatographic resolution and minimizing the band broadening in the cuvette by use of a make-up gas, the retention times of interest are freed from co-eluting background peaks. The instrumentation has been applied to the determination of ng l −1 concentrations of methyl- and inorganic mercury in Lake Constance, Germany and within the Lake Constance drinking water supply organization, Bodenseewasserversorgung (BWV). The accuracy for the sum of methyl- and inorganic mercury has been assessed by comparison with an independent method for total mercury based on AAS detection implemented at BWV. Relative detection limits using 1 litre water samples and 15 ml injections of the final hexane extract were 0.03 ng l −1 for methylmercury and 0.4 ng l −1 for inorganic mercury based on the 3j criterion.

Rapid sequential determination of inorganic mercury and methylmercury in natural waters by flow injection—cold vapour-atomic fluorescence spectrometry

A novel method for the rapid sequential determination of inorganic mercury and methylmercury in natural waters at the ng/l. level has been developed. Trace enrichment and separation of mercury species are achieved using a microcolumn of sulphydryl cotton which has a relatively high affinity for methylmercury. The limit of detection for methylmercury based on processing of a 0.5-ml sample volume was 6 ng/l. Application to river waters is demonstrated.