Determination Of Mercury Species Research Articles

Development of a new HPLC method for the determination of inorganic and methylmercury in biological samples with ICP-MS detection

In the present work a new HPLC method for the determination of mercury species in biological samples with ICP-MS detection was developed. Separation of inorganic (Hg2+) and methylmercury (CH3Hg+) was accomplished on a Hamilton PRP-X200 polymer-based cation-exchange column with a mobile phase of 50 mmol l−1 pyridine, 0.5% w/w L-cysteine and 5% v/w MeOH, at pH 2, within 8 min. The influence of chromatographic parameters, such as pH, salt concentration, organic modifier, and ion-pair reagent on the retention behaviour was evaluated. Based on peak areas, the experimental detection limits for inorganic and methylmercury were 0.05 and 0.08 μg Hg l−1, which corresponds to an absolute detection limit of 1.0 and 1.6 pg of mercury (20 μl injection volume). The liquid chromatographic method was successfully applied to the determination of inorganic and methylmercury in the two certified reference materials DORM-2 and DOLT-3, after a rapid and simple sample preparation procedure using hydrochloric acid.

Mercury speciation by CE: A review

CE methods for the speciation of inorganic and organomercury compounds are reviewed. Sample preparation, separation conditions and detection modes are discussed. Efficient separation and sensitive determination of mercury species by CE typically involves complexation with various thiols, chromogenic and other chelating agents; however, some methods do not require complexation. Spectrophotometric detection based on UV-visible absorption is by far the most commonly used. Hyphenated techniques, such as CE/inductively coupled plasma (ICP)-MS, hydride generation coupled to ICP-MS or atomic fluorescence spectrometry and CE/atomic absorption spectrometry are gaining popularity due to their high sensitivity and selectivity. Last, but not least, the potential and applications of electrochemical methods for detection of separated mercury species are outlined.

Vapour generation at a UV/TiO2 photocatalysis reaction device for determination and speciation of mercury by AFS and HPLC-AFS

In this study we report a method for direct vapor generation of mercury species on nano TiO2 under UV irradiation in the presence of a formic acid and sodium formate mixture as a hole scavenger. A novelly designed UV/TiO2 photocatalysis reaction device (UV/TiO2 PCRD) was used as an effective sample introduction unit and an interface for mercury species determination by atomic fluorescence spectrometry (AFS) and speciation by HPLC-AFS for the first time. The detection limits of 10, 20, 30 and 70 pg mL � 1 of mercury chloride, methylmercury chloride, ethylmercury chloride and phenylmercury chloride, respectively, were achieved by AFS using flow injection mode. Compared with the traditional KBH4/NaOH-HCl system, UV/TiO2 PCRD is a superior alternative for online vapor generation of Hg species.

Development of a mild mercaptoethanol extraction method for determination of mercury species in biological samples by HPLC–ICP-MS

A mild, efficient and convenient extraction method of using 2-mercaptoethanol contained extractant solution combined with an incubator shaker for determination of mercury species in biological samples by HPLC–ICP-MS has been developed. The effects of the concentration of 2-mercaptoethanol, the composition of the extractant solution and the shaking time on the efficiency of mercury extraction were evaluated. The optimization experiments indicated that the quantitative extraction of mercury species from biological samples could be achieved by using 0.1% (v/v) HCl, 0.1% (v/v) 2-mercapoethanol and 0.15% (m/v) KCl extractant solution in an incubator shaker for shaking overnight (about 12 h) at room temperature. The established method was validated by analysis of various biological certified reference materials, including NRCC DOLT-3 (dogfish liver), IAEA 436 (tuna fish), IAEA MA-B-3/TM (garfish filet), IAEA MA-M-2/TM (mussel tissue), GBW 08193 (bovine liver) and GBW 08572 (prawn). The analytical results of the reference materials were in good agreement with the certified or reference values of both methyl and total mercury, indicating that no distinguishable transformation between mercury species had occurred during the extraction and determination procedures. The limit of detection (LOD) for methyl (CH 3Hg +) and inorganic mercury (Hg 2+) by the method are both as 0.2 μg L −1. The relative standard deviation (R.S.D.s) for CH 3Hg + and Hg 2+ are 3.0% and 5.8%, respectively. The advantages of the developed extraction method are that (1) it is easy to operate in HPLC–ICP-MS for mercury species determination since the extracted solution can be directly injected into the HPLC column without pH adjustment and (2) the memory effect of mercury in the ICP-MS measurement system can be reduced.

Determination of mercury in polluted soils surrounding a chlor-alkali plant: Direct speciation by X-ray absorption spectroscopy techniques and preliminary geochemical characterisation of the area

Soil samples collected in the surroundings of a chlor-alkali plant in the Netherlands were characterised by synchrotron-based techniques and conventional analytical procedures, in order to evaluate the environmental impact of Hg emissions and other heavy metals present in these locations. Analysis of total metal content by inductively coupled plasma-optical spectroscopy (ICP-OES) revealed a heterogeneous contamination of Hg, with concentrations ranging from 4.3 to 1150 μg g −1. In addition, significant concentrations of Cu, Ni, Pb, Zn, Mn and principally Fe were also identified within the studied samples. Direct determination of mercury species by X-ray absorption near edge spectroscopy (XANES) showed inorganic Hg compounds to prevail in all soils, being Cinnabar (HgS red) and Corderoite (Hg 3S 2Cl 2) the main species. Nevertheless, more soluble mercury compounds, such as HgO and HgSO 4, have been also identified in significant proportion (from 6 to 20% of total mercury content), indicating a potential risk of mercury mobilisation. On the other hand, the application of sequential extraction schemes (SES) revealed large portions of weakly available Hg extracted in the residual fraction, while Hg associated to the exchangeable phase amounts as much as 19% of total Hg, thus, supporting the results obtained by XANES. Finally, synchrotron-based micro X-ray fluorescence (μ-XRF) was applied to identify qualitative trends on elemental associations in sample particles through a systematic mapping of its surface. In this concern, results show a well-defined correlation between Hg and Cu/Ni in the analysed particles. On the other hand, an absence of correlation between Hg and several other elements (Fe, Ti, Ca, Zn, Mn and S) was also observed. These effects have been attributed to chemical and physical interactions of mercury species on both enriched particles and sample matrices.

Determination of mercury species in fish reference materials by gas chromatography-atomic fluorescence detection after closed-vessel microwave-assisted extraction

A simple and rapid method has been developed for speciation analysis of inorganic mercury and monomethylmercury (MMHg) in biological tissues. The procedure is based on the quantitative closed-vessel microwave-assisted leaching of mercury from biological samples with an alkaline extractant. The extracted mercury species are ethylated and analysed by capillary gas chromatography coupled to an atomic fluorescence detector via pyrolysis (CGC-pyro-AFS). The coupling between capillary gas chromatography and atomic fluorescence detector was optimized with the aim of minimizing the detection limits and time necessary for the species-selective determination of mercury compounds. The use of closed-vessel microwave-assisted extraction along with no clean-up steps before the ethylation leads to a significant total analysis time decrease with respect to similar procedures. The detection limit was 2 pg for MMHg (as Hg) and 1 pg for inorganic mercury. The method was validated by the analysis of DORM-2 (dogfish muscle) and DOLT-3 (dogfish liver) certified reference materials. The inorganic mercury and methylmercury concentrations found were in good agreement with the certified values. Recovery studies of fish muscle tissue spiked with inorganic mercury and MMHg were done to check the reliability of the method. In all cases satisfactory recoveries (92–105%) were obtained.

Inter‐laboratory validation of EPA method 3200 for mercury speciation analysis using prepared soil reference materials

AbstractDeterminations of the concentration of individual mercury species from environmental samples have increased significantly over the past decade. The techniques used for the determination of mercury species in soils or sediments generally involve a series of analytical steps (extraction, separation, detection) that may all be prone to systematic errors. An inter‐laboratory validation study of the EPA draft method 3200 was conducted under the auspices of the United States Environmental Protection Agency on two specifically prepared soil matrices. The study was performed successfully by a limited number of participating laboratories. Evaluation of the data demonstrates that the method is more highly efficient for extracting the highly toxic methylmercury than inorganic mercury. The proposed method does not induce transformation of methylmercury to inorganic mercury. Copyright © 2004 John Wiley & Sons, Ltd.

Characterisation of Almadén mercury mine environment by XAS techniques

This manuscript describes the analysis and evaluation of mercury species present in three different types of samples (ore, slag and soil) belonging to the abandoned mining area of Almadén (Spain), by means of X-ray Absorption Spectroscopy (XAS) techniques. The applied methodology includes the analysis of possible interfering compounds by ICP-OES and the characterisation of solid samples by identification of heterogeneities using SEM-EDS technique prior to measurements at the synchrotron facilities (ESRF in Grenoble, France and HASYLAB in Hamburg, Germany) and subsequent analysis of data. Results show that cinnabar is the main species both in ore and soil samples, its concentration ranging from 41 to 77% of the total mercury content. On the other hand, metacinnabar (a polymorph of cinnabar) is shown to be the main species in slag samples (42-88%). Other mercury forms have been found in minor proportions (<30%), such as slightly soluble mercury salts (HgCl(2) and HgSO(4)) and HgO. This is the first time that Almadén-type mercury ores have been characterised by a synchrotron-based spectroscopic technique for a direct determination of mercury species. The conclusions presented in this report show the important similarities between Almadén and hot-spring type mercury mineral deposits, despite its different geological origin.

Application of neutron activation analysis for mercury species determination in scalp hair samples from Malaysia, Libya and Jordan

Neutron activation analysis was used to determine the levels of total mercury and methylmercury in hair samples obtained from 400 Malaysian (Kuala Lumpur), Libyan (Benghazi) and Jordanian (Amman) donors. Our results show that the level of total mercury in hair samples of the Malaysian group (3.38 mg·kg−1) was significantly higher than those of Libyan (0.81 mg·kg−1) and Jordanian groups (0.69 mg·kg−1). Likewise, a significant difference was found between the level of methylmercury of the Malaysian group (1.13 mg·kg−1) and those of the Libyan (0.04 mg·kg−1) and Jordanian groups (0.13 mg·kg−1). This difference could be attributed to the variation in life habits especially fish diet and to the local environment of each population. On the other hand, no significant differences were found between the level of total mercury and methylmercury in hair samples of the Libyan and Jordanian residents.

Interpretation of mercury depletion events observed at Ny-Ålesund, Svalbard during spring 2002

Mercury in different environmental compartments were measured at the Norwegian Arctic site Ny-Alesund (78°54'N, 11°53'E) during the period April 17 to May 14, 2002. Time-resolved speciated determination of mercury species in the atmosphere (Hg 0 (g), Hg +II (g) and Hg(particle)) and in snow were conducted. One major and two minor mercury depletion events occurred during the campaign. The depletion events were characterised by low concentrations of oxidised gaseous and airborne particulate mercury species. Elevated concentration of mercury in snow was detected during snowfall in conjunction with one mercury depletion episode. The observations have been analysed using meteorological and remote-sensing data. The results suggest that the low Hg 0 (g) concentrations observed were due to long range transport of mercury depleted air masses.

Determination of mercury species with a resin functionalized with a 1,2-bis( o-aminophenylthio)ethane moiety

A method for the simultaneous preconcentration and determination of Hg(II) and MeHg(I) at the ng ml −1 level has been developed. This method is based on solid phase extraction using a newly synthesized chelating resin containing nitrogen and sulphur donor sites of the 1,2-bis( o-aminophenylthio)ethane moiety that is very selective for mercury. The characterization of the resin has been carried out by elemental analyses, infrared spectral data, thermogravimetric analysis and metal ion capacities. The resin is highly selective for Hg(II) and MeHg(I) with an exchange capacity of 0.38 and 0.30 mmol g −1, respectively. Various parameters like pH, column flow rate, desorbing agents are optimized. Cold vapour atomic absorption spectrometry (CVAAS) was used to measure the concentration of both species of mercury. The calibration graph was linear upto 10 ng ml −1 with a 3 σ detection limit of 0.09 ng ml −1. The recovery of Hg(II) and MeHg(I) was found to be 98.9±2.0 and 98.0±1.1%, respectively. The method has been used for routine determination of trace levels of mercury species in natural waters to comply with more stringent regulations.

Application of cryofocusing hydride generation and atomic fluorescence detection for dissolved mercury species determination in natural water samples.

The concentration levels of mercury (Hg) species in natural water samples are usually low. Consequently, accurate analysis with low detection limits is still a major problem. In this work, a method was applied for the simultaneous direct determination of dissolved mercury species in water samples by on-line hydride generation (HG), cryogenic trapping (CT), gas chromatography (GC) and detection by atomic fluorescence spectrometry (AFS). The suitability of the method for real samples with different organic matter and chloride contents was evaluated by recovery experiments in synthetic and natural spiked water samples. The HG method was compared with other current available methods for mercury analysis with respect to the different fraction of mercury analysed, i.e. 'reactive', 'reducible' or total. HG derivatization and SnCl2 reduction (with and without previous oxidation with BrCl) were applied to synthetic and natural (spiked and non-spiked) water samples. The influence of chloride and dissolved organic matter concentrations was studied. The results suggest that the HG procedure is suitable for the simultaneous determination of Hg2+ and MeHg+ in surface water samples. Inorganic mercury analysed by HG (i.e. reducible) is close to the total inorganic mercury.

The speciation of inorganic and methylmercury in human hair by high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry

Inorganic and methylmercury content in human hair has previously been determined using different analytical techniques for each species. In this study a single method, allowing the separation and determination of mercury species in human hair, is developed. Using a HPLC-ICP-MS system it is possible to separate inorganic and methylmercury in hair, without any modifications to the existing instrumentation. The results showed that in order to determine methylmercury as well as inorganic mercury the hair sample must be cold digested with 2 ml of concentrated nitric acid plus 1 ml of hydrogen peroxide and that a minimum of 0.1 g hair is required. Hair washing procedures are also investigated to remove exogenously bound species. It is seen that when hair is soaked with simulated sweat solution containing both inorganic and methylmercury and then washed with 0.1 M HCl all the methylmercury, both existing and spiked, can be removed from the hair sample. However, only 65% of the spiked inorganic mercury can be removed by washing with 0.1 M HCl, the rest being irreversibly bound to the hair.

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.

Determination of Mercury Species by Capillary Column GC-QTAAS with Purge and Trap Preconcentration Technique

A GC-QTAAS procedure was developed for the determination of methylmercury and inorganic mercury(II) in biological samples. A capillary column DB-1 (J&W Scientific) was used for the separation of ethylated mercury species. Sodium tetraethylborate was used as derivatization reagent. When direct sample introduction did not provide low enough detection limits, a purge and trap preconcentration technique was developed, where the evolved mercury species were concentrated on Tenax-ta adsorbent. With this system the measuring range was between 0–5 ng (as Hg) for the different species (dimethylmercury, methylmercury and inorganic mercury(II)) in a 100 µl sample. The detection limits obtained for a 250 mg sample with the standard addition method were 72 µg/kg, 136 µg/kg and 224 µg/kg for dimethylmercury, monomethylmercury and inorganic mercury(II), respectively. The method was successfully applied to the determination of mercury species in the dogfish certified standard reference material (DOLT-2).

Use of Ultrasound in Sample Preparation for the Determination of Mercury Species by Cold-Vapor Atomic Absorption Spectrometry

Ultrasound was used for the intensification of sample preparation in the determination of different mercury species in brines and solutions of sodium chloride and common salt. Procedures were proposed for the determination of total mercury and inorganic, organic, and methyl mercury species.

Field sampling, preconcentration and determination of mercury species in river waters

A simple field sampling strategy for determination and speciation of inorganic mercury and methylmercury in river waters is described. River water samples are collected in situ by passing them with a pump through a minicolumn packed with C 18 modified with sodium diethyldithiocarbamate. This packing is able to isolate and retain the desired mercury species. Minicolumns loaded with the analytes are then returned to the laboratory where mercury species are eluted with 500 μl of 5% thiourea in 0.5% HCl. A detailed study of the construction of these minicolumns and the stability of the mercury species retained in the packing is presented. The separation of the two mercury species was carried out by liquid chromatography using a cysteine solution as mobile phase and final detection was accomplished by inductively coupled plasma mass spectrometry. Between-column relative standard deviations of 12% at the 200 ng l −1 Hg level and limits of detection of 5.2 ng l −1 for inorganic mercury and 5.6 ng l −1 for methylmercury are obtained. The method has been applied to mercury speciation in clean river waters of the Asturias region of Spain.

Preliminary evaluation of adsorbent-based mercury removal systems for gas condensate

Mercury can be present in gas condensate in its metallic form and/or as organometallic compounds with boiling points comparable to that of the range of the condensate. The damage caused to industrial plants, particularly petrochemical plants, by the presence of certain mercury species can be financially crippling especially when unscheduled shut-downs are forced. Speciation of the mercury content of gas condensates is vital in the evaluation of an adsorbent system’s efficiency and for the development, improvement and monitoring of the performance of newly developed or commercially available mercury removal systems. However, with the mercury species content being at such low levels, great demands are made of an analytical technique. Three commercially available mercury removal systems designated AA, BB, and CC were tested under pilot plant conditions to evaluate their performance. System AA was a two-stage process involving a species conversion step prior to trapping of mercury on an alumina-adsorbent impregnated with a metal sulphide. Systems BB and CC were single-stage trapping processes using sulphide impregnated carbon and molecular sieves, respectively. Both real and substitute condensate sample i.e. hexane containing dimethyl mercury (DMM), diethyl mercury (DEM) and dibutyl mercury (DBM) species, were used in the trials. The determination of total mercury was carried out by a proven method which involved the direct vaporisation with subsequent adsorption of mercury species onto a gold-coated silica trap maintained at 200°C. To release metallic mercury, the trap was heated at 900°C and the analyte determined by atomic fluorescence spectrometry (AFS). The determination of mercury species in the samples was carried out by direct injection using gas chromatography coupled, via a pyrolysis unit, with atomic fluorescence detection. All three mercury-removal systems AA, BB and CC showed a reduction in the mercury content of the final condensate streams. In the two-stage system, AA, the hydrogenolysis reactor converted some of the organomercury present in the gas condensate feed to its elemental form. However, the elemental mercury measured in the liquid product from this first reactor was only about 30% of the total mercury content. Incomplete conversion of the organomercury species to mercury metal by this reactor may be due to competition between the organomercury species and the unsaturated compounds in the matrix during the hydrogenolysis reaction. The second reactor, for mercury trapping, was able to adsorb efficiently elemental mercury present in the liquid stream (the product from the first reactor) but was unable to remove the organomercury content from the condensate stream. For the single-stage adsorbent system BB, the efficiency in removing the species DMM, DEM and DBM from n-hexane hydrocarbon samples was 100% with no indication of mercury present in the product stream over an 8 h continuous run. For the adsorbent system CC, the efficiency of removal for different mercury species in n-hexane was variable. While DMM and DEM showed a consistent removal range of 50–80%, the DBM was efficiently adsorbed, but only for a short period (>80% at 2 h) and it was rapidly released back into the product stream after 4 h.

Determination of mercury species by capillary zone electrophoresis-inductively coupled plasma mass spectrometry: a comparison of two spray chamber–nebulizer combinations

A method based on capillary zone electrophoresis (CZE) separation and inductively coupled plasma mass spectrometry (ICP-MS) detection is presented for the determination of methylmercury and inorgan ...

Species specific isotope dilution calibration for determination of mercury species by gas chromatography coupled to inductively coupled plasma- or furnace atomisation plasma ionisation-mass spectrometry

Standard solutions of (CH3)2Hg, CH3HgCl and HgCl2 were prepared in toluene from isotopically enriched mercury. Methods for synthesising (CH3)2Hg and CH3HgCl, from HgCl2, were developed with reaction yields of 95.2% and 92.7%, respectively, without noticeable loss of isotope. Isotopically enriched species standards were then used for species specific isotope dilution calibration and method assurance tests for mercury species determination. An interface was built to couple a gas chromatograph (GC) to an inductively coupled plasma mass spectrometer (ICP-MS) that resulted in rapid and efficient transfer of organic mercury compounds eluted from natural gas condensates. Oxygen, introduced to the plasma auxiliary gas, reduced matrix interferences and improved sensitivity by a factor of two. The GC-ICP-MS method with species specific isotope dilution calibration gave recovery values of 97.7 ± 2.0, 104.1 ± 0.7 and 106.6 ± 2.1% for (CH3)2Hg, CH3HgCl and HgCl2, respectively, in natural gas condensate compared to a standard solution of the species in toluene. Detection limits of the three species, calculated from 3s of the peak areas derived from 20 pg of the species (as Hg) in solution, were 8, 2 and 3 pg. Furnace atomisation plasma ionisation mass spectrometry (FAPIMS) was also evaluated as a detector with the GC methodology. When the plasma was operated with optimised conditions for the generation of elemental ions, recoveries were 100.0 ± 2.9, 98.3 ± 1.5 and 97.5 ± 1.2% for (CH3)2Hg, CH3HgCl and HgCl2 in a 10% condensate solution, and a detection limit of 33 pg was obtained for methylmercury. A plasma was also generated and sustained with reduced rf power and graphite furnace temperature so that molecular ions and fragments were produced and detected by the same spectrometer, which demonstrated the potential of FAPIMS as a sensitive elemental detector additionally capable of providing molecular mass spectra for the identification of species eluted from a GC column.