Determination Of Total Hg Research Articles

Gas-Liquid Separator Modified on CV-AAS System for Determination of Total Hg in the Industrial Wastewater Samples


 
 
 The research about the utilization of modified gas-liquid separators in the determination of Hg ions by using the Cold Vapor Atomic Absorption Spectrophotometer (CV-AAS) method has been done. To optimize the measurement results, several parameters that affect the hydride generator have been studied. Some specified essential parameters are the type and concentration of acid, the level of SnCl2 as a reducing agent, sample volume and the analytical performance such as linearity (r), detection limit (LOD) and quantitation limit (LOQ), repeatability (% RSD), and accuracy have been studied. The results of the research showed the gas-liquid separator modified can be used instead of commercial gas- liquid separators. It was showed by the repeatability value as % RSD < 2/3 CV Horwitz values, the LOD was 0.2530 μg/mL, and the LOQ was 0.8432 μg/mL. The accuracy of this method was good shown by a recovery percentage of 101.6%. Based on the result of this research, the modified of gas-liquid separator can be used for the determination of Hg ions by using the CV-AAS method with valid results
 
 

Simple and rapid method for the determination of mercury in human hair by cold vapour generation atomic fluorescence spectrometry

The aim of the study was to develop and validate a rapid method for the analysis of the total Hg concentration in human hair, specifically, Eritrean hair. For total Hg determination, the cold vapour generation atomic fluorescence spectrometry (CV-AFS) technique was used, and the results were compared with those of the more frequently used advanced mercury analyser (AMA). Samples were prepared by washing the hair and collecting two samples; the first was used for the direct analysis of Hg by AMA and the second was digested for Hg determination by CV-AFS. The results of field hair sample analysis indicate that the two data sets were fully comparable (median: AMA, 0.11 mg kg−1; CV-AFS, 0.12 mg kg−1) and were not statistically different (Mann–Whitney test, p-value = .944). The two techniques showed results with good coefficients of determination (R2 = 0.98) despite the different operating ranges. The AMA and CV-AFS methods were validated using a certified reference hair sample, yielding, respectively, trueness biases of 7.4% and 7.2%, intra-day repeatabilities (relative standard deviation (RSD), %) of 3.2% and 6.0%, inter-day reproducibilities (RSD, %) of 5.3% and 8.2%, and expanded standard measurement uncertainties of 8.9% and 17%, respectively. Analyses of blank measurements by AMA and CV-AFS yielded a detection limit of 0.0004 and 0.004 mg kg−1 of Hg for 5 and 20 mg samples of human hair, respectively. Both techniques are simple, easy to use, and relatively inexpensive, and the method validation parameters indicate sensitivity, precision, and reliability. In conclusion, the use of AMA should be considered over CV-AFS in hair analysis to reduce sample handling and, consequently, lower the risk of contamination, use fewer samples, and allow more economical analyses. In contrast, CV-AFS using optimised fast digestion in an open vessel heated in a water bath instead of AMA allows short analysis times and automation, thus allowing high sample throughput for routine analysis and human biomonitoring studies.

Proficiency testing as a tool to assess quality of data: the experience of the EU Reference Laboratory for chemical elements in food of animal origin

Abstract Quality and reliability of analytical results are, in general, key issues for all laboratories but become a top priority for laboratories accredited according to ISO/IEC 17025:2005. In this international standard the proficiency testing (PT) is regarded as a means to assure the validity of results. Nowadays, the proved competence of laboratories is an essential requirement especially for that structures that are involved in the official controls aimed at ensuring the safety of EU food products and the public health. To guarantee the EU consumers, the Council and the Commission have designated 28 European Union Reference Laboratories (EURLs) for food and feed, whose main role is to contribute to the standardization of analytical methods and to the harmonization of performance among the EU National Reference Laboratories (NRLs) to reach a comparable level of quality in the analytical data among all Member States. With this aim, the organization of PTs is a task that each EURL has to accomplish. Over the last 15 years, the EURL for chemical elements in food of animal origin (EURL-CEFAO) have organized 32 PTs on determination of total As, Cd, Pb and total Hg in meat, milk, fish and offal for the benefit of its network of NRLs. Some specific aspects of this activity will be discussed (e.g. preparation and characterization of PT materials, statistical evaluation of data, follow-up actions). Finally, based on the EURL-CEFAO experience, it will be demonstrated that the participation into PTs on a regular basis can result in an improvement of the laboratory’s performance as well as in the harmonization of the results submitted by participants.

Reflux open-vessel digestion system can overcome volatilization loss in mercury speciation analysis

Volatilization loss of analytes in open-vessel digestion is a concern for mercury speciation analysis. Loss of Hg0 vapour can be overcome by using oxidative digestion media, while loss of aerosols can be circumvented by complete condensation under sub-boiling-point heating. Using a simple system that consisted of a block heater and culture tubes, two digestion protocols were developed for determination of total Hg (tHg) and inorganic Hg (iHg). The resulting Hg++ was selectively reduced by SnCl2 to Hg0, which was detected by atomic fluorescence spectrometry (AFS). MeHg+ was oxidized to Hg++ to yield tHg and calculated from the difference. These methods were validated using certified reference material (CRM) DORM-4, and applied to seafood analysis with 3.6 and 3.2 ng g−1 (dry weight) limit of detection for iHg and tHg, respectively. Using only off-the-shelf components, these methods gained cost, simplicity, and parallel operation advantages.

Eco-scale non-chromatographic method for mercury speciation in fish using formic acid extraction and UV–Vis photochemical vapor generation capacitively coupled plasma microtorch optical emission spectrometry

An eco-scale method based on UV–Vis photochemical vapor generation and detection in a capacitively coupled plasma microtorch by optical emission measurement with a low resolution microspectrometer was developed for Hg speciation as Hg2+ and CH3Hg+ in seafood. Our proposal provides a simpler, greener analytical method in terms of sample preparation and derivatization, and use of small-scale instrumentation. Coupling of UV–Vis photo-reactor with plasma microtorch is a very promising approach to develop eco-scale methods for Hg speciation in seafood with major advantages to classical methods. The most distinctive characteristic of the method is the use of a single reagent, formic acid, for the extraction of Hg species from solid sample and as medium for the photo-induced cold vapor generation. An amount of 0.2 g lyophilized sample was subjected to ultrasound assisted extraction in 10 ml HCOOH 98–100% at 50 °C for 3 h then on line UV–Vis photo-induced derivatization in 0.6 mol l−1 HCOOH was achieved. Total Hg and Hg2+ species were quantified against Hg2+ external standard solutions by measuring emission at 253.652 nm in a low power/low Ar consumption (15 W/100 ml min−1) plasma source with Maya2000 Pro (Ocean Optics) microspectrometer. Under UV exposure both Hg2+ and CH3Hg+ species were converted with same efficiency to cold vapor, while natural room light (Vis) achieved selectively derivatization of Hg2+. Concentration of CH3Hg+ was obtained by subtracting Hg2+ amount from total. The proposed method was compared with Thermal Decomposition Atomic Absorption Spectrometry eco-scale method developed for the determination of total Hg from solid sample and CH3Hg+ according to the procedure recommended by the European Commission. The limits of detection/quantification provided by the proposed method were 9/27 μg kg−1 total Hg and 4.8/14.4 μg kg−1 Hg2+. Study of accuracy against certified reference materials gave recovery of 99 ± 6% total Hg, 99 ± 9% Hg2+ and 99 ± 10% CH3Hg+, while precisions assessed from measurements on real sample were 2.6–10.2%, 2.0–13.4% and 5.3–14.5% respectively, similar to those in the reference method.

Cleaning and sampling protocol for analysis of mercury and dissolved organic matter in freshwater systems

Mercury (Hg), and in particular its methylated form (methylmercury, MeHg), is a hazardous substance with the potential to produce significant adverse neurological and other health effects. Enhanced anthropogenic emissions and long-range transport of atmospheric Hg have increased Hg concentrations above background levels in aquatic systems. In this context, the Minamata Convention, a global legally binding agreement that seeks to prevent human exposure to Hg, was signed and enforced by 128 countries, and today more than 90 Parties have ratified it. All these Parties have committed to develop Hg monitoring programs to report the effectiveness of the convention. For this purpose, we provide a standardized cleaning and water sampling protocol for the determination of total-Hg and MeHg in freshwaters at ambient levels. As Hg and organic matter are tightly bound, the protocol also describes sample collection for dissolved organic carbon (DOC) concentration and characterization of dissolved organic matter (DOM) composition by fluorescence spectroscopy. This protocol is highly useful to non-experts without a prior background in Hg sampling and analysis, and can serve as a useful basis for national monitoring programs. Furthermore, this protocol should help increase quantitative inventories of DOC, inorganic-Hg (IHg) and MeHg concentrations and DOM composition in freshwater, which are severely lacking at a global scale.•Provides a standardized method to collect water samples for IHg, MeHg, DOC and DOM composition from freshwater ecosystems.

Mercury speciation in fish tissue by eco-scale thermal decomposition atomic absorption spectrometry: method validation and risk exposure to methylmercury

A non-chromatographic method for Hg speciation in fish muscle using eco-scale thermal desorption atomic absorption spectrometry was validated according to the demands of the Decisions 2007/333/EC, 2011/836/EC and 2002/657/EC. The method is based on the determination of total Hg in solid sample and MeHg+, respectively, after double liquid–liquid extraction (47% HBr, toluene, 1% l-cysteine) according to a procedure recommended by the European Commission. The method was applied for the speciation of Hg in fish muscle to asses the weekly intake and health risk exposure to MeHg+. The method provided calibration coefficients better than 0.999, limits of detection of 0.2 µg kg−1 total Hg and 3.0 µg kg−1 MeHg+. The accuracy of the method assessed by the analysis of CRMs was 100 ± 9% for total Hg and 101 ± 13% for MeHg+ for a coverage factor k = 2. The figures of merit of the method comply with the requirements in the European legislation. Total Hg in the analyzed fish species was in the range 12–108 µg kg−1 wet mass, of which 83–97% as MeHg+. Although significant variation in total Hg was observed among fish species, no differences in terms of distribution of organic and inorganic Hg species were identified. No risk exposure to MeHg+ was ascertained from muscle fish consumption from reliable sources, since weekly intake was below 30% of provisional tolerable weekly intake of 1.6 µg kg−1 body weight. Speciation is recommended as MeHg+ is much more helpful than total Hg to evaluate the dietary risk exposure.

Mercury speciation in seafood using non-chromatographic chemical vapor generation capacitively coupled plasma microtorch optical emission spectrometry method – Evaluation of methylmercury exposure

A non-chromatographic method was developed for Hg speciation as CH3Hg+ and Hg2+ using simple instrumentation based on optical emission spectrometry in a low power and low Ar consumption capacitively coupled plasma microtorch and detection with a low resolution microspectrometer. The method is based on (i) determination of total Hg after sample digestion in nitric acid-hydrogen peroxide mixture, derivatization to cold vapor with 20% SnCl2 in 15% HCl medium; (ii) determination of CH3Hg+ separated by double liquid-liquid extraction as recommended in JRC Technical Report of European Commission, followed by photochemical vapor generation in 0.6 mol l−1 formic acid and (iii) calculation of the inorganic (Hg2+) species as difference. The calibration curve was generated with external Hg2+ standards in 5% (v/v) HCl for total Hg determination and 0.6 mol l−1 HCOOH medium for CH3Hg+, respectively. The method was validated against certified reference materials and successfully applied for Hg speciation in most consumed fish species. The limits of detection of the method were 2 and 3 μg kg−1 CH3Hg+ and total Hg respectively, which made possible quantification of 6/9 μg kg−1 organic/total Hg. The method proved to be accurate with recovery of 101 ± 10% (total Hg), 100 ± 8% (CH3Hg+) and 102 ± 13% (Hg2+), and precision in the range 2.4–7.8% (total Hg), 2.4–11.9% (CH3Hg+) and 3.8–14.0% (Hg2+). The speciation method allowed accurate and precise determination of CH3Hg+ and Hg2+ even when the organic species represented more than 98% of total Hg. Total Hg in fish depended on variety but in all cases it was below the maximum admitted level (0.5 mg kg−1). Methylmercury represented 22.3–93.3% of total Hg, with higher weights in salmon, carp, mackerel and hake and lower in cod, trout and pangasius irrespective of total Hg. Evaluation of risk exposure to CH3Hg+ from occasional fish consumption based on Provisional Tolerable Weekly Intake seems to be much more informative than the concentration of total or organic Hg species. It has been concluded from our study that there is no health risk from exposure to methylmercury for 300–1000/60-200 g weekly fish consumption by adult/child when fish comes from reliable sources.

Optimization and validation of the methods for the total mercury and methylmercury determination in breast milk

The objective of the work was to develop and validate methods for the total Hg and methylmercury (MeHg) in breast milk that could be further used to obtain first data on chemical contamination of French breast milk. For total Hg determination, the potential of two techniques, namely Advanced Mercury Analyzer (AMA) and ICP MS, was compared. For MeHg determination, ICP MS detection associated to a quantification by isotopic dilution was used and the potential of a preliminary separation by gas or liquid chromatography was evaluated and discussed. The optimization studies have shown that AMA for total Hg determination and HPLC – ID – ICP MS, after a preconcentration step by freeze-drying, for MeHg quantification were the most relevant methods to use for epidemiologic studies. The figures of merit for both methods were evaluated by means of accuracy profiles in terms of limits of quantification (1.82 and 1.35µg Hg/kg dry weight, corresponding to 0.22 and 0.16µg Hg/kg wet basis for total Hg and MeHg, respectively), repeatability (2–11% and 3–8% for total Hg and MeHg respectively), intermediate precision reproducibility (4–12% and 4–8% for total Hg and MeHg respectively) and trueness bias (−0.1–9% and −4–0% for total Hg and MeHg respectively). The methods were then applied to 180 breast milk samples. Total Hg concentrations ranged from <LD to 16.9µg Hg/kg wet basis (<LD to 142µg Hg/kg dry weight) and the MeHg contents from <LD to 0.43µg Hg/kg wet basis (<LD to 3.67µg Hg/kg dry weight).

Human exposure and risk assessment associated with mercury contamination in artisanal gold mining areas in the Brazilian Amazon.

Mercury (Hg) contamination is an issue of concern in the Amazon region due to potential health effects associated with Hg exposure in artisanal gold mining areas. The study presents a human health risk assessment associated with Hg vapor inhalation and MeHg-contaminated fish ingestion, as well as Hg determination in urine, blood, and hair, of human populations (about 325 miners and 321 non-miners) from two gold mining areas in the Brazilian Amazon (São Chico and Creporizinho, Pará State). In São Chico and Creporizinho, 73 fish specimens of 13 freshwater species, and 161 specimens of 11 species, were collected for total Hg determination, respectively. The hazard quotient (HQ) is a risk indicator which defines the ratio of the exposure level and the toxicological reference dose and was applied to determine the threat of MeHg exposure. The mean Hg concentrations in fish from São Chico and Creporizinho were 0.83 ± 0.43 and 0.36 ± 0.33 μg/g, respectively. More than 60 and 22 % of fish collected in São Chico and Creporizinho, respectively, were above the Hg limit (0.5 μg/g) recommended by WHO for human consumption. For all sampling sites, HQ resulted from 1.5 to 28.5, except for the reference area. In Creporizinho, the values of HQ are close to 2 for most sites, whereas in São Chico, there is a hot spot of MeHg contamination in fish (A2-São Chico Reservoir) with the highest risk level (HQ = 28) associated with its human consumption. Mean Hg concentrations in urine, blood, and hair samples indicated that the miners group (in São Chico: urine = 17.37 μg/L; blood = 27.74 μg/L; hair = 4.50 μg/g and in Creporizinho: urine = 13.75 μg/L; blood = 25.23 μg/L; hair: 4.58 μg/g) was more exposed to mercury compared to non-miners (in São Chico: urine = 5.73 μg/L; blood = 16.50 μg/L; hair = 3.16 μg/g and in Creporizinho: urine = 3.91 μg/L; blood = 21.04 μg/L, hair = 1.88 μg/g). These high Hg levels (found not only in miners but also in non-miners who live near the mining areas) are likely to be related to a potential hazard due to exposure to both Hg vapor by inhalation and to MeHg-contaminated fish ingestion.

Determination of total cadmium, lead, arsenic, mercury and inorganic arsenic in mushrooms: outcome of IMEP-116 and IMEP-39

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate General of the European Commission, operates the International Measurement Evaluation Program (IMEP). IMEP organises inter-laboratory comparisons in support of European Union policies. This paper presents the results of two proficiency tests (PTs): IMEP-116 and IMEP-39, organised for the determination of total Cd, Pb, As, Hg and inorganic As (iAs) in mushrooms. Participation in IMEP-116 was restricted to National Reference Laboratories (NRLs) officially appointed by national authorities in European Union member states. IMEP-39 was open to all other laboratories wishing to participate. Thirty-seven participants from 25 countries reported results in IMEP-116, and 62 laboratories from 36 countries reported for the IMEP-39 study. Both PTs were organised in support to Regulation (EC) No. 1881/2006, which sets the maximum levels for certain contaminants in food. The test item used in both PTs was a blend of mushrooms of the variety shiitake (Lentinula edodes). Five laboratories, with demonstrated measurement capability in the field, provided results to establish the assigned values (Xref). The standard uncertainties associated to the assigned values (uref) were calculated by combining the uncertainty of the characterisation (uchar) with a contribution for homogeneity (ubb) and for stability (ust), whilst uchar was calculated following ISO 13528. Laboratory results were rated with z- and zeta (ζ)-scores in accordance with ISO 13528. The standard deviation for proficiency assessment, σp, ranged from 10% to 20% depending on the analyte. The percentage of satisfactory z-scores ranged from 81% (iAs) to 97% (total Cd) in IMEP-116 and from 64% (iAs) to 84% (total Hg) in IMEP-39.

Development of a method for total Hg determination in oil samples by cold vapor atomic absorption spectrometry after its extraction induced by emulsion breaking

This work reports the development of a novel extraction method for total Hg determination in oil samples. After extracting Hg from samples it was quantified in the extracts by cold vapor atomic absorption spectrometry (CV-AAS), employing a laboratory-made gas–liquid separator (GLS) and NaBH4 as reducing agent. The extraction of Hg from samples was carried out by extraction induced by emulsion breaking (EIEB), which is based on the formation and breaking of water-in-oil emulsion between the oil samples and an extractant solution containing an emulsifying agent (surfactant) and nitric acid. Operational parameters of the GLS were evaluated in order to set the best performance of the measurement system. In these studies it was proven that the volume of sample and the concentration of HCl added to the sample extracts had significant influence on Hg response. The best conditions were achieved by adding 0.5mL of a 0.3molL−1 HCl solution on 1mL of sample extract. The extraction conditions were also optimized. The highest efficiency was observed when 4mL of a solution containing 2.5% triton X-100 and 15% v/v HNO3 were employed for the extraction of Hg contained in 20mL of sample. Emulsion breaking was performed by heating at 80°C and took approximately 20min. The limit of quantification of the method was 1.9µgL−1 and recovery percentages between 80% and 103% were observed when spiked samples (2 and 10µgL−1) of diesel oil, biodiesel and mineral oil were analyzed.

Determination of Total Mercury in Fish Tissue Using a Low-Cost Cold Vapor Capacitively Coupled Plasma Microtorch Optical Emission Microspectrometer: Comparison with Direct Mercury Determination by Thermal Decomposition Atomic Absorption Spectrometry

A method for total Hg determination in fish tissue using cold vapor capacitively coupled plasma microtorch optical emission spectrometry was evaluated. The low-cost miniaturized analytical system includes a low power plasma microtorch (10 W) and low Ar consumption (150 ml min−1) and a QE65Pro microspectrometer as detector. Lyophilized fish tissues were microwave-assisted digested in HNO3–H2O2 mixture, brought in 5 % (v/v) HCl, then Hg vapor was chemically generated with 20 % SnCl2 solution stabilized in 15 % (v/v) HCl. The figures of merit of the proposed method were evaluated by analyzing certified reference materials and test samples and compared to those of the well-established thermal decomposition atomic absorption spectrometry method. The analytical characteristics (limits of detection and quantification, precision, and accuracy) comply with requirements for Hg determination in seafood set out in Decisions 2007/333/EC and 2002/657/EC. The limits of detection and quantification of the proposed method were 3 and 9 μg kg−1 Hg in dry mass, similar to those in thermal decomposition atomic absorption spectrometry. The precision was between 1.8 and 5.5 % for concentrations in the range 0.18–0.76 mg kg−1 Hg, while the accuracy was 99.7 ± 3.0 %. The significance tests revealed no difference between the results obtained by the two methods. The proposed miniaturized spectrometric equipment could be the subject of prototyping as low-cost instrumentation for designed applications in seafood control.

Feed premix: a difficult matrix for the accurate determination of trace elements – the outcome of IMEP-114 and IMEP-36

This paper presents the outcome of two proficiency tests (IMEP-114/36) running in parallel, which focused on the determination of total As, Cd, Pb, Hg and Sn in feed premixes. Both exercises aimed to test the performance of laboratories measuring trace elements in feed, in compliance with Directive 2002/32/EC of the European Parliament and of the Council on undesirable substances in animal feed. IMEP-114 was run for the European Union National Reference Laboratories, while IMEP-36 was open to all food control laboratories that wished to participate. In total 80 laboratories from 37 countries registered to both proficiency tests, from which 75 laboratories reported results. The test material used in this exercise was commercially available feed premix, which was processed, bottled, labelled and dispatched to participants. The performance of the participating laboratories was similar in both proficiency tests and was very good in the case of total Cd and less satisfactory for total As and total Pb. For total Sn only one-third of the participants reported results, from which 33% performed satisfactorily. Thirty-four participants reported results for total Hg, although the expert laboratories stated that the mass fraction for that measurand was below the limit of detection of the method used. An evaluation of the reasons that could be at the basis of unsatisfactory results has been carried out and is presented here.

Submicron silica spheres decorated with silver nanoparticles as a new effective sorbent for inorganic mercury in surface waters

An analytical method using silica supported silver nanoparticles as a novel sorbent for the enrichment and determination of inorganic mercury (iHg) in surface water samples has been developed. Silver nanoparticles (AgNPs) were synthesized by a completely green procedure and were deposited onto the amine functionalized surface of silica submicrospheres (SiO2-NH2). The prepared nanocomposite material (SiO2/AgNPs) was characterized by transmission electron microscopy, UV-vis spectroscopy, X-ray diffraction and atomic force microscopy. The sorption and desorption characteristics of the nanosorbent SiO2/AgNPs toward Hg species were investigated by a batch method. An excellent separation of iHg and methylHg was achieved in 20 minutes at pH 2. The high selectivity of the SiO2/AgNPs toward iHg was explained by Hg(ii) reduction and subsequent silver-mercury amalgam formation. The analytical procedure for the enrichment and determination of inorganic mercury in surface waters was developed based on solid phase extraction and ICP-MS measurements. The total Hg content was determined after water sample mineralization. The recoveries reached for iHg in different surface waters e.g. river and Black sea water samples varied from 96-101%. The limits of quantification are 0.002 μg L(-1) and 0.004 μg L(-1) for iHg and total Hg, respectively; the relative standard deviations varied in the ranges of 5-9% and 6-11% for iHg and total Hg, respectively, for Hg content from 0.005 to 0.2 μg L(-1). The accuracy of the procedure developed for total Hg determination was confirmed by a comparative analysis of surface river (ICP-MS) and sea (CV AFS) waters.

Characterization of soils from an industrial complex contaminated with elemental mercury

Historical use of liquid elemental mercury (Hg(0)l) at the Y-12 National Security Complex in Oak Ridge, TN, USA, resulted in large deposits of Hg(0)l in the soils. The fate and distribution of the spilled Hg(0) are not well characterized. In this study we evaluated analytical tools for characterizing the speciation of Hg in the contaminated soils and then used the analytical techniques to examine the speciation of Hg in two soil cores collected at the site. These include x-ray fluorescence (XRF), soil Hg(0) headspace analysis, and total Hg determination by acid digestion coupled with cold vapor atomic absorption (HgT). XRF was not found to be suitable for evaluating Hg concentrations in heterogeneous soils containing low concentration of Hg or Hg(0) because Hg concentrations determined using this method were lower than those determined by HgT analysis and the XRF detection limit is 20 mg/kg. Hg(0)g headspace analysis coupled with HgT measurements yielded good results for examining the presence of Hg(0)l in soils and the speciation of Hg. The two soil cores are highly heterogeneous in both the depth and extent of Hg contamination, with Hg concentrations ranging from 0.05 to 8400mg/kg. In the first core, Hg(0)l was distributed throughout the 3.2m depth, whereas the second core, from a location 12m away, contained Hg(0)l in a 0.3m zone only. Sequential extractions showed organically associated Hg dominant at depths with low Hg concentration. Soil from the zone of groundwater saturation showed reducing conditions and the Hg is likely present as Hg-sulfide species. At this depth, lateral Hg transport in the groundwater may be a source of Hg detected in the soil at the deeper soil depths. Overall, characterization of soils containing Hg(0)l is difficult because of the heterogeneous distribution of Hg within the soils. This is exacerbated in industrial facilities where fill materials make up much of the soils and historical and continued reworking of the subsurface has remobilized the Hg.

Determination of Mercury (Hg) in Sediment by a Sequential Injection (SI) System With Cold Vapor Generation Atomic Fluorescence Spectrometry (CVAFS) Detection After a Rapid and Mild Microwave-Assisted Digestion

A simple and rapid method has been developed for the determination of total Hg in drainage sediment. The method is performed by using a sequential injection (SI) system with cold vapor generation atomic fluorescence spectrometry (CVAFS) after a closed microwave assisted digestion. Digestion was carried out at a temperature of 140°C for 5 minutes using a mixture of 10% HCl + 50% HNO3 +40% H2O as digestion acid media. Stability experiment revealed that the extracted samples were stable in 24 hours. The SI–CVAFS system was well optimized. At optimized conditions, the detection limit of the method was 0.5 ng/g−1. Relative standard deviation (RSD) for the complete procedure by the analysis of the 10 digestions was 3.7%. The method was validated against 3 drainage sediment certified reference materials: GSD-2, GSD-9, and GSD-10 and successfully applied to the determination of Hg in the sediment of Pi River, China.

Evaluation of drying conditions of fish tissues for inorganic mercury and methylmercury speciation analysis

The influence of drying conditions on the behavior of Hg species (Hg2+ and CH3Hg+) present in fish tissues was evaluated. Drying conditions were evaluated for six fish species using air circulation drying oven in different temperatures (50 to 175°C) and lyophilization (0.25mm Hg, −2°C). Evaluation of drying step was based on losses and conversions of original Hg species after each drying condition. The extraction efficiency was determined by comparing the concentration of total Hg in digested samples (wet digestion in closed system using HNO3) with extracted Hg using l-cysteine solution. Chemical vapor generation-inductively coupled plasma mass spectrometry (CVG-ICP-MS) and liquid chromatography-chemical vapor generation-inductively coupled plasma mass spectrometry (LC-CVG-ICP-MS) were used for the determination of total Hg and Hg species, respectively. The accuracy was evaluated using certified reference materials and an agreement better than 97% with certified values was obtained for CH3Hg+ and total Hg. The relative standard deviation of the proposed method was below 5.5%. Limit of detection of 1.7 and 2.3ngg−1 as Hg was obtained for Hg2+ and CH3Hg+, respectively. Results showed that with drying temperatures above 100°C losses and conversions of CH3Hg+ to Hg2+ can occur for some fish species.

Analysis of mercury and selenium during subcritical water treatment of fish tissue by various atomic spectrometric methods

Subcritical water treatment of biomass and food waste (especially marine product) is now very attractive in terms of the production of useful chemicals. Big marine fish, such as tuna, usually contain a high level of Hg, which is considered safe because of the sequestration by Se species. In this study, such fish tissues were treated with subcritical water, and the resulting aqueous phase was analyzed for Hg and Se to estimate the dissolution behavior of these toxic elements. The determination of total Hg in the aqueous phase was carried out by heat vaporization atomic absorption spectrometry (HVAAS), while that of Se was done by inductively coupled plasma mass spectrometry (ICP-MS). The dissolution behavior of those elements was favorably monitored. The speciation of Hg in the aqueous phase was performed by HPLC with cold vapor atomic fluorescence spectrometry aided by UV irradiation–oxidation (HPLC-UV-CVAFS), and the Hg species detected was mainly methylated Hg. For the speciation of Se, size-exclusion chromatography (SEC) with ICP-MS was attempted to use, and it was found that high molecular and insoluble Se species, which were originally contained in the tissue, was gradually decomposed into lower molecular hydrophilic species, and dissolved in the aqueous phase.

Comparative study of sample decomposition methods for the determination of total Hg in crude oil and related products

This paper presents a comparative study of three decomposition methods (A, B and C) for the determination of total Hg (THg) in crude oil and related products by cold vapor atomic absorption spectrometry (CV-AAS). Methods A and B employed closed-pressurized (HPA-S) and cold-finger systems, respectively. Method C employed a pyrolysis system. Some procedures were introduced to improve the weighing of samples in quartz boats, as well as for the cleaning of the boats, after sample pyrolysis. Also, the weighing of samples and their transfer into the cold-finger vessels, which were too long and heavy, were facilitated. Furthermore, the digestion time of the sample in the HPA-S was optimized. Spiked certified reference materials and one spiked crude oil sample were used for accuracy tests. Satisfactory recoveries (75–123%), repeatability and reproducibility (RSD≤14%) for the THg results were obtained for all tested methods. Also, the THg concentrations in crude oil and oil sludge samples obtained by all tested methods were statistically similar. Although method B is commercially available in a low cost and can simultaneously pre-treat many samples, it showed the highest blank concentration, the highest LOQ, the longest digestion time and a high burst risk.