Cold Vapor Generation Atomic Absorption Research Articles

Local and landscape factors influencing mercury distribution in water, bottom sediment, and biota from lakes of the Araguaia River floodplain, Central Brazil

Mercury (Hg) is a chemical element widely present in the Earth's crust. However, its high toxicity and ability to accumulate in organisms and biomagnify through food chains characterize it as a global pollutant of primary control. We assessed total mercury concentrations ([THg]) in abiotic and biotic compartments from 98 floodplain lakes associated with the Araguaia River and six tributaries (Midwest Brazil). [THg] quantification in water was performed by cold vapor atomic fluorescence spectroscopy. [THg] in bottom sediment was assessed using cold vapor generation atomic absorption spectrophotometry, while [THg] in macrophyte, periphyton, and plankton were quantified by thermal decomposition atomic absorption spectrometry. Hotspots of [THg] in water, bottom sediment, and macrophytes were determined in areas impacted by pasture and urban areas. In contrast, hotspots of [THg] in periphyton and forest fires were determined in preserved areas downstream. [THg] in plankton did not show a clear spatial distribution pattern. The mean bioaccumulation factor order was plankton (2.3 ± 1.8) > periphyton (1.3 ± 0.9) > macrophytes (0.7 ± 0.4) (KW = 55.09, p < 0.0001). Higher [THg] in water and bottom sediment were associated with high pH (R2adj = 0.118, p = 0.004) and organic matter (R2adj = 0.244, p < 0.0001). [THg] in macrophytes were positively influenced by [THg] in water (R2adj = 0.063, p = 0.024) and sediment (R2adj = 0.105, p = 0.007). [THg] in periphyton are positively related to forest fires (R2adj = 0.156, p = 0.009) and [THg] in macrophytes (R2adj = 0.061, p = 0.03) and negatively related to lake depth (R2adj = 0.045, p = 0.02). The transfer of Hg from water and sediment to the biota is limited. However, the progressive increase of the bioaccumulation factor between macrophyte, periphyton, and plankton may indicate Hg biomagnification along the food chain of the Araguaia River floodplain.

Use of an aminated Amberlite XAD-4 column coupled to flow injection cold vapour generation atomic absorption spectrometry for mercury speciation in water and fish tissue samples

An aminated Amberlite XAD-resin as a solid phase extractant was tested for speciation of inorganic mercury, Hg(II) and methylmercury, MeHg(I) in water and fish tissue samples. It was found that Hg(II) and MeHg(I) ions could be simultaneously retained by a column filled with AAXAD-4 resin at pH 4 and the sequential quantitative elutions of Hg(II) and MeHg(I) were achieved using 10 mL of 0.1%(m/v) thiourea in 3%(v/v) HCl and 10 mL of 6 mol L−1 HCl, respectively. Hg(II) in the eluent was directly determined and MeHg(I) in the second eluent is quantified using FI-CVG-AAS after its oxidative digestion with KMnO4. The limits of detection for Hg(II) and MeHg(I) ions were found to be 0.148 and 0.157 µg L−1, respectively. The method was validated by analysing a certified reference material. The relative errors for Hg(II), MeHg(I) and T-Hg were in range of −1.8% and −3.2%.

Suitable extraction of soils and sediments for mercury species and determination combined with the cold vapor generation atomic absorption spectrometry technique

This work reports a fast and efficient procedure for mercury species extraction using Universol® as extractor reagent in soil and sediment samples combined with the cold vapor generation atomic absorption spectrometry (CV AAS) technique. Hg total was determined after oxidation CH3Hg+ to Hg2+ with KMnO4 and reduction Hg2+ to Hg0 with NaBH4. To ensure specificity and sensitivity in the Hg2+ determination, L-cysteine was added before the reduction with SnCl2 to form complex with organic mercury species. Recovery values of between 98 and 102% were obtained for Hgtotal, and 96–100% for Hg2+. The relative standard deviations were lower than 2.7%. The detection limits were 0.07 and 0.08mgkg−1 for Hgtotal and Hg2+, respectively. The use of Universol® reagent combined with the CV AAS technique proved to be a simple and efficient procedure for the determination of Hgtotal and Hg2+ in soil and sediment samples without interconversion of species allowing chemical speciation studies.

In-atomizer atom trapping on gold nanoparticles for sensitive determination of mercury by flow injection cold vapor generation atomic absorption spectrometry

An in-atomizer atom trapping method based on coating gold nanoparticles onto the inner wall of a quartz tube atomizer was firstly developed and combined with flow injection cold vapor generation for the accurate determination of mercury at low μg L−1 levels by atomic absorption spectrometry. Mercury vapor generated by reducing Hg2+ with hydrochloric acid–tetrahydroborate was efficiently trapped on the surface of gold nanoparticles that were coated on the interior wall of the quartz tube atomizer prior to the determination. In situ desorption and determination of mercury was achieved by increasing the voltage (thus the temperature) to 30 V. The influence of instrumental parameters and experimental conditions on the generation, trapping and desorption of mercury vapor, as well as interference from concomitant elemental ions was investigated. A detection limit of 0.01 μg L−1 was obtained based on a 5.0 mL sampling volume. The precision was better than 4.0% at 0.5 μg L−1. Three spiked water samples and two Certified Reference Materials (dogfish muscle, DORM-4 and human hair powder GBW07601a) were analyzed to validate the accuracy of the proposed method.

Mercury species determination by task specific ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction combined with cold vapour generation atomic absorption spectrometry

Task specific ionic liquid-based ultrasound-assisted dispersive liquid–liquid microextraction (TSIL USA DLLME) combined with cold vapour atomic absorption spectrometry (CV AAS) for determination of mercury species in water and biological samples was developed. The proposed procedure was free of volatile organic solvents, and there was no need to use any dispersive solvents and complexing agents, in contrast to standard DLLME. Analytical signals were obtained without the back-extraction of the mercury species from the TSIL phase into an aqueous phase prior to their determination by CV AAS. The reducing agent Sn2+ could reduce Hg2+ and CH3Hg+ for determination of total mercury. Some essential parameters of the microextraction and cold vapour generation, such as the pH of sample solution, volume of the ionic liquid, ultrasonication time, cooling time, centrifugation time, matrix interferences and salt effect have been studied. Under optimal conditions, high extraction efficiency was achieved for the extraction of 1.0ngmL−1 of Hg2+ and 5ngmL−1 CH3Hg+ in 10.0mL of water solution employing 30μL of methyltrioctylammonium thiosalicylate as the extraction solvent. The enrichment factor for the method was 310 for Hg2+ and 200 for CH3Hg+. The detection limits were 0.03ngmL−1 for Hg2+ and 0.4ngmL−1 for CH3Hg+ respectively. The accuracy of the proposed method was evaluated by analysis of the Certified Reference Materials (NRCC DOLT-2, NIST 1643e). The method was applied to analysis of the tap, river, lake and sea water samples. The recoveries for reference materials and spiked samples were in the range of 95-103%.

Survey of total mercury and arsenic content in infant cereals marketed in Spain and estimated dietary intake

Due to the fact that infants and children are especially sensitive to mercury and arsenic exposure, predominantly through diet, a strict control of the most widely consumed infant foods, especially infant cereals, is of paramount importance. Levels of both total mercury and arsenic in 91 different infant cereals from ten different manufacturers in Spain were determined by flow injection adapted to cold vapor and hydride generation atomic absorption spectrometry, respectively. Cereals were assessed in terms of the different types, the predominating cereal in the formulation, the added ingredients, and whether the cereal was organically or conventionally obtained. In general, the content of toxic elements (median (Q1; Q3)) found in infant cereals based on conventionally obtained raw materials (n = 74, Hg: 2.11 (0.42; 4.58), As: 21.0 (9.4; 50.9) μg Kg−1) was lower than in cereals produced by organic methods (n = 17, Hg: 5.48 (4.54; 7.64), As: 96.3 (87.5; 152.3) μg Kg−1). Mercury content in infant cereals shows the higher values in those formulations with ingredients susceptible to particulate contamination such as gluten-free or cacao-based cereals. The highest arsenic content appears in the rice-based cereals. The mercury and the inorganic arsenic dietary intakes for infants fed on the infant cereals studied were assessed, taking into account the different stages of growth. Organic infant cereals based on cocoa showed the highest risk intakes of mercury, very close to exceeding the intake reference. Just the opposite, 95% of the organically produced infant cereals and 70% of the conventional gluten-free infant cereals showed an inadmissible risk of arsenic intake. Thus, it seems prudent to call for continued efforts in standardizing routine quality control and in reducing arsenic levels in infant cereals; in addition it is essential that relevant legislation be established and regulated by EC regarding these two toxic elements.

Simultaneously determination of methyl and inorganic mercury in fish species by cold vapour generation atomic absorption spectrometry

A simple and rapid non-chromatographic method was developed to determine methylmercury (MeHg) and inorganic mercury (iHg) levels in muscles tissues of 10 freshwater fish species. The MeHg and iHg were determined by cold vapour atomic absorption spectrometry after alkaline wet digestion of samples. The digested samples were reduced sequentially with stannous chloride and sodium tetrahydroborate for iHg and MeHg, respectively. Parameters such as carrier gas flow rate (argon), volume of oxidizing and potassium persulphate solutions were investigated in detail. The accuracy of the technique was evaluated by using certified reference material (DORM-2) and spiking the both Hg species in muscles tissue of a fish. The limits of detection were 0.117 and 0.133 μg kg(-1) for MeHg and iHg, respectively. The concentrations of MeHg and iHg in muscles tissues of ten fish species were found in the range of (28.4-56.3) and (3.01-8.11) μg kg(-1), respectively.

Colloidal mercury (Hg) distribution in soil samples by sedimentation field-flow fractionation coupled to mercury cold vapour generation atomic absorption spectroscopy

Diverse analytical techniques are available to determine the particle size distribution of potentially toxic elements in matrices of environmental interest such as soil, sediments, freshwater and groundwater. However, a single technique is often not exhaustive enough to determine both particle size distribution and element concentration. In the present work, the investigation of mercury in soil samples collected from a polluted industrial site was performed by using a new analytical approach which makes use of sedimentation field-flow fractionation (SdFFF) coupled to cold vapour generation electrothermal atomic absorption spectroscopy (CV-ETAAS). The Hg concentration in the SdFFF fractions revealed a broad distribution from about 0.1 to 1 μm, roughly following the particle size distributions, presenting a maximum at about 400-700 nm in diameter. A correlation between the concentration of Hg in the colloidal fraction and organic matter (O.M.) content in the soil samples was also found. However, this correlation is less likely to be related to Hg sorption to soil O.M. but rather to the presence of colloidal mercuric sulfide particles whose size is probably controlled by the occurrence of dissolved O.M. The presence of O.M. could have prevented the aggregation of smaller particles, leading to an accumulation of mercuric sulfides in the colloidal fraction. In this respect, particle size distribution of soil samples can help to understand the role played by colloidal particles in mobilising mercury (also as insoluble compounds) and provide a significant contribution in determining the environmental impact of this toxic element.

Solid phase extraction of cadmium on 2-mercaptobenzothiazole loaded on sulfur powder in the medium of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and cold vapor generation–atomic absorption spectrometric determination

A novel solid phase extractor for preconcentration of cadmium at ng L −1 levels has been developed. Cadmium ions were retained on a column packed with sulfur powder modified with 2-mercaptobenzothiazole (2-MBT) in the medium of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] +PF 6 −) ionic liquid. The presence of ionic liquid during modification of sulfur enhanced the retention of cadmium ions on the column. The retained cadmium ions were eluted with 2 mol L −1 solution of HCl and measured by cold vapor generation–atomic absorption spectrometry (CVG–AAS). By using reaction cell-gas liquid separator (RC-GLS), gaseous cadmium vapors were produced and reached the atomic absorption spectrometer, instantaneously. The influence of different variables on both processes of solid phase extraction and CVG–AAS determination of cadmium ions was investigated. The calibration curve was linear in the range of 10–200 ng L −1of cadmium in the initial solution with r = 0.9992 ( n = 8) under optimum conditions. The limit of detection based on three times the standard deviation of the blank (3S b, n = 10) was 4.6 ng L −1. The relative standard deviation (R.S.D.) of 25 and 150 ng L −1 of cadmium was 4.1 and 2.2% ( n = 8), respectively. The procedure was validated by the analysis of a certified reference material (DORM-3), water and fish samples.

Mercury speciation in urban landfill leachate by cold vapor generation atomic absorption spectrometry using ion exchange and amalgamation

0 is produced and then measured by cold vapor atomic absorption spectrometry (CV AAS). Hg org does not interact with the resin and is mixed with NaBH 4 at the exit of the column producing volatile species of Hg that are then amalgamated by a gauze of Au/Pt. Mercury is removed from the gauze by heating to 600 °C and subsequently measured by CV AAS. For Hg inorg and Hg org speciation in urban landfill leachate, the samples are centrifuged, filtered and treated with HCl. The detection limits (3 s) of Hg inorg and Hg org are 9 and 12 ng L -1 of Hg, respectively. The analysis frequency is 22 h -1 .

Mercury fatal intoxication: Two case reports

We report two cases of fatal intoxications with mercury, one intentional and the other allegedly resulting from a drug formulation mistake. Both cases occurred in the year of 2004. The first case refers to a man who ingested a great portion of a mercuric chloride solution. He attended a hospital emergency, submitted to treatment, but died after 49 days. In the second case, a woman applied on the chest skin an ointment containing a great quantity of mercury bromide. After 7 days of treatment in the hospital, she died. In both cases, samples of tissues and organs were collected at autopsy for mercury analysis. Because methylation of mercury in humans after exposure to metallic or inorganic mercury is almost unknown, both total mercury and methylmercury were quantified in the post- mortem samples. The quantifications were carried out by Cold Vapour Generation Atomic Absorption Spectrometry for total mercury and by HPLC-UV for methylmercury. The total mercury contents found in the post- mortem fluid and tissue samples were consentaneous with mercury poisoning. For the first case, the concentrations found, expressed in μg/g wet weight, were in the liver 49.9, lung 3.27 and brain 0.33, and for blood 11.7 μg/mL. For the second case, the concentrations expressed in μg/g wet weight were in the liver 46.6, lung 14.6, brain 0.21, kidney 77.7, stomach 7.12, spleen 6.4 and heart 2.34, and for blood and urine 2.95 and 1.40 μg/mL, respectively. Only in the first case was methylmercury found and quantified in liver (1.70 μg/g wet weight) and in blood (0.15 μg/mL) samples.

Hg 0 oxidative absorption by K 2S 2O 8 solution catalyzed by Ag + and Cu 2+

The aqueous phase oxidation of gaseous elemental mercury (Hg 0) by potassium persulfate (K 2S 2O 8, KPS) catalyzed by Ag + and Cu 2+ was investigated using a glass bubble column reactor. Concentrations of gaseous Hg 0 and aqueous Hg 2+ were measured by cold vapor generation atomic absorption spectrometry (CVAAS). The effects of several experimental parameters on the oxidation were studied; these include different types of catalysts, pHs and concentrations of potassium persulfate, temperatures, Hg 0 inlet concentrations and tertiary butanol (TBA). The results showed that the removal efficiency of Hg 0 increased with increasing concentration of potassium persulfate and catalysts Ag +, Cu 2+ and Ag + provided better catalytic effect than Cu 2+. For example, in the presence of 5.0 mmol l −1 KPS, the mercury removal efficiency could reach 75.4 and 97.0% for an Ag + concentration of 0.1 and 0.3 mmol l −1, respectively, and 69.8 and 81.9% for 0.1 and 0.3 mmol l −1 Cu 2+. On the other hand, high temperature and the introduction of TBA negatively affect the oxidation. Furthermore, the removal efficiency of Hg 0 was much greater in neutral solution than in either acidic or alkaline solution. But the influence of pH was almost eliminated upon the addition of Ag + and Cu 2+, and high Hg 0 inlet concentration also has positive impact on the removal efficiency of Hg 0. The possible catalytic oxidation mechanism of gaseous mercury by KPS was also proposed.

Determination of trace mercury in geological samples by direct slurry sampling cold vapor generation atomic absorption spectrometry

A new method based on ultrasonic slurry sampling atomic absorption spectrometry (AAS) was established for the determination of trace mercury in geological samples by use of recently developed mercury cold vapor generation using formic acid under ultraviolet (UV) irradiation. The generated mercury cold vapor was rapidly separated from the matrix and swept into a T-tube for the measurement of atomic absorbance. Under the optimal experimental conditions, up to 1000-fold of Cu(II), Co(II), Ni(II), Cr(VI), Mn(II), Fe(III), and Zn(II) caused no significant interference with the determination of 50 µg L−1 Hg. The limit of detection at sub-ppb level was obtained for mercury. The method was applied to the determination of mercury in geological samples with satisfactory results.

Solid state reactions in the platinum–mercury system

Abstract Thermogravimetry, Differential Scanning Calorimetry and other analytical techniques (Energy Dispersive X-ray Analysis; Scanning Electron Microscopy; Mapping Surface; X-ray Diffraction; Inductively Coupled Plasma Atomic Emission Spectroscopy and Cold Vapor Generation Atomic Absorption Spectroscopy) have been used to study the reaction of mercury with platinum foils. The results suggest that, when heated, the electrodeposited Hg film reacts with Pt to form intermetallic compounds each having a different stability, indicated by at least three mass loss steps. Intermetallic compounds such as PtHg4, PtHg and PtHg2 were characterized by XRD. These intermetallic compounds were the main products formed on the surface of the samples after partial removal of bulk mercury via thermal desorption. The Pt(Hg) solid solution formation caused great surface instability, attributed to the atomic size factor between Hg and Pt, facilitating the acid solution’s attack to the surface.

Comparison of three strategies to evaluate uncertainty from in-house validation data. A case study: mercury determination in sediments

In the present paper, three approaches are compared for the evaluation of the combined uncertainty in the determination of mercury in aquatic sediments by an aqua regia extraction procedure. For this, the data obtained in validation studies from five certified reference materials (CRMs), covering a range of concentrations from 0.8 to 130 mg kg(-1) of mercury and analysed by three atomic spectroscopic techniques (cold vapour generation atomic fluorescence spectrometry, CV-AFS, cold vapour generation atomic absorption spectroscopy, and inductively coupled plasma mass spectroscopy), were considered. The combined uncertainty was firstly assessed by considering separately the data obtained for each CRM analysed (approach A). Moreover, this assessment was also performed with two other calculation approaches (B and C) based on the pooled data obtained from the validation step. The comparison of the results obtained for the different techniques showed a clear bias effect when using CV-AFS with nitric acid as a diluent. In relation to the strategies tested for the combined uncertainty assessment, approach C proved to be the easiest and friendliest method for uncertainty assessment.

Effect of Exhaustion Hood Flow Rate in Flow Injection Cold Vapor and Hydride Generation Atomic Absorption Spectrometry

The effect of exhaustion hood flow rate in the laboratory was investigated. It has been observed that this parameter significantly affects the analytical signal. This effect was more evident in cold vapor (CV) atomic absorption spectrometry (AAS) signal when unheated quartz T‐tube atomizer (QTA) was used as atom cell. At maximum exhaustion hood flow rate, the peak height and peak area values for Cd decreased to 36% and 35%, respectively, of those obtained under no exhaustion. When CV cell with both ends covered with quartz plates was used, exhaustion hood flow rate did not affect the analytical signal significantly. The exhaustion hood flow rate effect was less pronounced in case of heated QTA as compared to unheated QTA. In addition to exhaustion hood flow rate, the air movements around the atom cell also influenced the analytical signal and precision of the measurement.

Methylmercury and inorganic mercury determination in fish by cold vapour generation atomic absorption spectrometry

Abstract Given that organic mercury is more dangerous than the inorganic form and that it is converted into methylmercury by biological methylation, we have studied and optimized a simple method for measuring both organic and inorganic mercury contents in fish, using a spectroscopic vapour generation technique, with a sequential reduction of the digested sample with stannous chloride and sodium tetrahydroborate. Prior to applying the method the sample was subjected to alkaline wet digestion. Due to the matrix interferences calibration curves with matrix addition were needed for mercury determinations. The analytical parameters of the method were: linearity from 10 to 200 ng of Hg in the reduction vessel; detection limit: 125 and 183 ng/g fresh sample for inorganic mercury and methylmercury, respectively; precision (RSD%): 9.8 and 10.1 for inorganic mercury and methylmercury, respectively; accuracy: reference material (Dorm-2-NRC-CNRC) for methylmercury; value found 4504±272 ng/g; certified value 4470±320 ng/g. The method offers the advantage of not requiring special equipment to measure inorganic and organic mercury simultaneously in a sample. To evaluate its usefulness it was applied to nine different types of fish and mussels.

Determination of inorganic mercury in biological tissues by cold vapor atomic absorption spectrometry following tetramethylammonium hydroxide solubilization

A rapid and simple method for the quantification of inorganic and total mercury in biological tissues using flow injection cold vapor generation atomic absorption spectrometry is presented. Samples were solubilized using tetramethylammonium hydroxide. The inorganic Hg was released by on-line addition of L-cysteine and then reduced to metallic Hg by SnCl2. The detection limit for inorganic mercury was 0.1 µg l–1 and the precision of determination was better than 2% (RSD) at 20 µg l–1. The proposed method was validated by the analyses of a suite of certified marine biological reference materials, DORM-2 (dogfish muscle), DOLT-2 (dogfish liver) and TORT-2 (lobster hepatopancreas).

The use of emulsions for the determination of methylmercury and inorganic mercury in fish-eggs oil by cold vapor generation in a flow injection system with atomic absorption spectrometric detection.

An on-line time based injection system used in conjunction with cold vapor generation atomic absorption spectrometry and microwave-aided oxidation with potassium persulfate has been developed for the determination of the different mercury species in fish-eggs oil samples. A three-phase surfactant-oil-water emulsion produced an advantageous flow when a peristaltic pump was used to introduce the highly viscous sample into the system. The optimum proportion of the oil-water mixture ratio was 2:3 v/v with a Tween 20 surfactant concentration in the emulsion of 0.008% v/v. Inorganic mercury was determined after reduction with sodium borohydride while total mercury was determined after an oxidation step with persulfate prior to the reduction step to elemental mercury with the same reducing agent. The difference between total and inorganic mercury determined the organomercury content in samples. A linear calibration graph was obtained in the range 0.1-20 micrograms l-1 of Hg2+ by injecting 0.7 ml of samples. The detection limits based on 3 sigma of the blank signals were 0.11 and 0.12 microgram l-1 for total and inorganic mercury, respectively. The relative standard deviation of ten independent measurements were 2.8 and 2.2% for 10 micrograms l-1 and 8.8 and 9.0% for 0.1 microgram l-1 amounts of total and inorganic mercury, respectively. The recoveries of 0.3, 0.6 and 8 micrograms l-1 of inorganic and organic mercury added to fish-eggs oil samples ranged from 93.0 to 94.8% and from 100 to 106%, respectively. Good agreement with those values obtained for total mercury content in real samples by electrothermal atomic absorption spectrometry was also obtained, differences between mean values were < 7%. With the proposed procedure, 22 proteropterous catfish-eggs oil samples from the northwestern coast of Venezuela were measured; while the organic mercury lay in the range 2.0 and 3.3 micrograms l-1, inorganic mercury was not detected.

Application of microwave digestion to trace organoelement determination in water samples

Microwave digestion is a powerful tool for converting various types of samples into a solution ready for instrumental measurement. In trace analysis for heavy metals in water and waste water it may show some limitations due to the comparatively high dilution of the digestion reagent by the water sample itself. This is proved in this study with organically bound elements to be analyzed, after digestion, by cold vapor or hydride generation atomic absorption spectrometry, because these techniques require the elements to be completely mineralized. The experiments were carried out with 2-[(ethylmercury)thio]benzoic acid, d,l-selenomethionine and tetraphenylarsonium chloride using microwave digestion devices allowing high- and low-pressure digestion. The selenium compound yielded satisfactory results with both digestion modes; in contrast the arsenic compound yielded very low recoveries under all test conditions applied. The mercury compound gave good recoveries only with the high-pressure digestion device. Low-pressure digestion revealed significantly lower results. High concentrations of organic matter may lead to incomplete digestion and low results because of the development of high carbon dioxide pressure which causes the feed-back system of the microwave device to reduce microwave power and, hence, temperature in the batch. Also the digestion mixture may play an important role as shown by the organoarsenic compound. The quoted limitations should be taken into account in water analysis particularly if it is intended to incorporate microwave digestion in standardized procedures.