Cold Vapor Atomic Absorption Spectrophotometry Research Articles

Determination of Methylmercury After Supercritical Fluid Extraction

A method, using supercritical fluid extraction, for determining methylmercury in seafood has been developed to eliminate use of toxic organic solvents. Seafood samples were treated with 1N NaOH and then acidified with HCl to release CH3HgCl. After mixing the sample with cellulose powder (40 mesh) containing stearic acid modifier at 5 mg/g, the extraction was performed with supercritical CO2 under the following conditions: pressure, 200 atm; temperature, 50 degrees C; time, 20 min; and trap, 0.01N Na2S2O3 in a conical tube immersed in a flask of warm water to prevent freezing. The extract was then analyzed by a suitable method, such as cold-vapor atomic absorption spectrophotometry. The accuracy of the procedure was verified by analyzing biological standard reference materials. Several commercial seafood samples and spikes have been analyzed.

Determination of Lead, Cadmium, Mercury, and Copper Concentrations in Duck Eggs in Taiwan

Samples of duck eggs were collected from 65 farms distributed in 6 counties in Taiwan to analyze the contents of Pb, Cd, Hg, and Cu in albumen and yolk. Lead, Cd, and Cu determinations were performed by microwave digestion together with atomic absorption spectrophotometry, whereas Hg was anlayzed by sulfuric acid-nitric acid digestion and cold vapor atomic absorption spectrophotometry. Expressed on a wet weight basis, the average concentrations (ranges) of the four metals were as follows: Pb, 13.6 ng/g (.8 to 27.5) in albumen and 84.7ng/g (44.8 to 224.7) in yolk; Cd, 1.8 ng/g (<.5 to 4.4) in albumen and 3.8 ng/g (<1.0 to 5.7) in yolk; Hg, 17.8 ng/g (2.5 to 47.5) in albumen and 9.7 ng/g (1.2 to 20) in yolk; Cu, .83 μg/g (.56 to 1.08) in albumen and 1.36 μg/g (.95 to 1.95) in yolk. Comparison of the calculated daily intakes of Pb, Cd, and Hg from eggs with the World Health Organization-Food Agriculture Organization provisional tolerated daily intakes suggest that duck eggs are safe with respect to the contents of the three metals. Eggs are poor sources of Cu, supplying less than 2% of the Recommended Dietary Allowance.

Mercury content in rat teeth after administration of organic and inorganic mercury. The effects of interrupted exposure and of selenite.

Rat molars are indicators of exposure concentration and target organ content in chronic mercury vapor exposure. We wished to study the accumulation and persistence of organic and inorganic mercury in rat teeth and the effect of selenium on mercury retention. Male Wistar rats received either inorganic or organic mercury (with or without addition of selenite), selenite only, or no mercury or selenite (controls) in the drinking water for 4 weeks. Group A was killed after exposure. Group B was killed 20 weeks later. The mercury content was measured by cold-vapor atomic absorption spectrophotometry. The mercury content in the molars in group B was 66% and 77% less than in group A after inorganic and organic exposure, respectively. In the incisors the corresponding reductions were 90% and 97%. Selenite had limited effect on mercury retention in group A and none in group B. We suggest that rat molars and, by inference, human deciduous teeth may serve as indicators of organic and inorganic mercury exposure.

Toxic metals in forest biota around the steel works of Rautaruukki Oy, Raahe, Finland

The levels of Al, Mn, Fe, Cu, Zn, Cd and Hg in bioindicators, which included eight species of plants, two species of bark beetles and three species of Formica ants, were studied in the coniferous forests around the Rautaruukki steel works, Raahe, Finland. The major objective was to determine the degree and extent of the metal deposition expressed by the different bioindicators. Samples were collected along 30 km long observation lines from the factory to the NE and the S, respectively. Mercury analyses were performed by cold vapor atomic absorption spectrophotometry and the other metals by flame atomic absorption spectrophotometry. Elevated levels of Fe were detected in all bioindicators up to a distance of 10 km, and of Al, Zn and Cu up to a distance of 3 km from the steel works. The highest metal concentrations were observed in the epiphytic lichen ( Hypogymnia physodes) and in the moss ( Pleurozium schreberi) and included maxima of 28 000 mg kg −1 for Fe, 1500 mg kg −1 for Al and 900 mg kg −1 for Mn. According to the synthetic index of Grodzinska (1978), the pollution load of these multiple pollutants has reached the level at which forests are, in general, damaged. In the Raahe area, this damage potential covered a distance of up to 6 km to the NE and 3 km to the S. Bark beetles as well as Formica ants act as good bioindicators for Fe and Al, but not for other metals. This study shows that the best biological species for indicating air pollution from iron and steel works for the chosen metals are: H. physodes for Fe, Mn and Cu; P. schreberi and H. physodes for Zn and Al and M. bifolium for Cd.

The ability of the unicellular giant algaAcetabularia sp.to bioconcentrate aquatic mercury in whole and anucleated cells

The uptake of mercury by the marine alga Acetabularia sp. was studied using mercury chloride (HgCl2). The algae were exposed to water contaminated with HgCl2 for various periods of time: 5 min. ‐ 6 h. and 1 day ‐ 7 days. Hg was measured by cold vapor atomic absorption spectrophotometry and the results obtained indicate that Acetabularia is a good absorbent of aquatic mercury. Moreover, the uptake of Hg appeared not to be highly affected either by the presence of a protein synthesis inhibitor (Cycloheximide), or by the absence of the nucleus in long term contamination.

The effect of the electrode potential on the release of mercury from dental amalgam.

The effect of the electrode potential on the rate of mercury dissolution from the matrix phase (gamma 1) of dental amalgam was investigated. Specimens of the Ag-Hg phase, with and without dissolved tin, were exposed to synthetic saliva and maintained at various potentials by means of a potentiostat. The amount of dissolved mercury was determined after 24 h by cold-vapor Atomic Absorption Spectrophotometry. Anodic polarization curves for the gamma 1 specimens and pure silver and mercury were also recorded. The results for the Ag-Hg phase showed a potential-independent dissolution rate between -0.6 and -0.1 V (SCE), followed by a sharp increase. Mercury dissolution from the Ag-Hg-Sn phase was much slower than from the tin-free gamma 1 phase, and potential-independent to +0.05 V (SCE); a sharp increase in mercury dissolution was observed at +0.1 V (SCE). The anodic polarization curves for the Ag-Hg-Sn phase indicated passivity between -0.67 V and +0.1 V (SCE), but no clear passivation for the Ag-Hg specimen, silver, or mercury. The results show that in the potential-independent region, mercury dissolved in the atomic form from both the tin-free and tin-containing gamma 1 phase. The increase in dissolution in the upper range of potentials was tentatively attributed to selective anodic dissolution of silver and an onset of electrochemical dissolution. The results indicate that the rate of mercury release from the gamma 1 phase of dental amalgam was not affected by potential changes due to alloying or galvanic contacts unless the potential exceeded some critical value.

Measurement of Arsenic and Mercury Concentrations by Hydride and Cold Vapor Atomic Absorption Spectrophotometry

The main objectives of this study were to assess arsenic and mercury exposure and to promote understanding of biological monitoring. Workplace activities observed involved bending and pressing of metal sheets, electrowelding, electroplating, machining, and motorcycle muffler assembly. The arsenic and mercury in the specimens of nonoccupational controls and workers were determined by hydride atomic absorption spectrophotometry and cold vapor atomic absorption spectrophotometry. The results showed that total arsenic levels in the exposed workers were significantly higher than those in nonexposed controls (Mann-Whitney test, p<0.0001), and that there is a risk of arsenic poisoning to the workers engaged in motorcycle muffler assembly. The total mercury levels in the exposed workers were no different than in controls (p>0.05).

MEASUREMENT OF ARSENIC AND MERCURY CONCENTRATIONS BY HYDRIDE AND COLD VAPOR ATOMIC ABSORPTION SPECTROPHOTOMETRY

The main objectives of this study were to assess arsenic and mercury exposure and to promote understanding of biological monitoring. Workplace activities observed involved bending and pressing of metal sheets, electrowelding, electroplating, machining, and motorcycle muffler assembly. The arsenic and mercury in the specimens of nonoccupational controls and workers were determined by hydride atomic absorption spectrophotometry and cold vapor atomic absorption spectrophotometry. The results showed that total arsenic levels in the exposed workers were significantly higher than those in nonexposed controls (Mann-Whitney test, p 0.05).

Detection of Mercury in Rat Spinal Cord and Dorsal Root Ganglia after Exposure to Mercury Vapor

Adult male Wistar rats were exposed to mercury vapor, 50 μg Hg/m 3, 6 hr/day, 5 days/week, over 1-, 2-, 3-, 4-, 6-, and 8-week periods. Sections from the spinal cord and dorsal root ganglia from spinal levels C 1, C 5, T 6, and L 1 were stained with the autometallographical technique and the distribution of mercury deposits described at light and electron microscopical levels. A quantitative analysis of the amount of mercury in blocks of the spinal cord was performed using cold vapor atomic absorption spectrophotometry. After an exposure period of 2 weeks, silver-enhanced mercury grains could be observed in spinal cord neurons located in Rexed laminae IV-X. Ventral horn motoneurons were heavily stained in all of the spinal cord segments. Ependymal cells and glial cells of both the spinal gray and white matter contained cytoplasmatic mercury accumulations in rats exposed to mercury vapor for 4 weeks. In the dorsal root ganglia, only ganglion cells showed a faint mercury staining and the amount of staining was notably less than that seen in the ventral horn motoneurons. At the ultrastructural level, mercury was seen primarily within lysosomes of target cells. The quantitative mercury measurements demonstrated that spinal cords from rats exposed to mercury vapor for 6 or 8 weeks contained a significantly higher concentration of mercury than those from control animals.

Mercury Contents of Indicators and Target Organs in Rats After Long-Term, Low-Level, Mercury Vapor Exposure

Five groups of Wistar rats received graded concentrations of mercury vapor from 10 to 100 μg Hg/m 3 6 hr. 5 days a week, from 4 to 11 weeks of age. One group breathing ambient air served as controls. The mercury levels of the indicators blood, hair, molars, and incisors as well as the target organs kidney cortex, cerebrum, cerebellum, liver, lung, spleen, tongue, and femur were measured by cold-vapor atomic absorption spectrophotometry. The mercury vapor had no negative influence on the weight gain of the animals. The results showed that the kidney cortex had the highest concentration of mercury. The mercury contents of all the indicators and all the target organs, with the exception of femur, were positively and significantly correlated with the exposure concentration. The rat molars had the highest correlation coefficient with the kidney mercury values, but no indicator had a significant correlation with all target organs. Rat molars are to some degree comparable to human deciduous teeth regarding time of mineralization and eruption. Based on the results presented in this study, we tentatively suggest that human deciduous teeth can be useful indicators of chronic mercury exposure not only at the exposure concentration level, but also as indicators of the mercury uptake in organs such as kidney and cerebrum.

Determination of Arsenic and Mercury Concentrations in Urine of Patients with Blackfoot Disease.

Blackfoot disease (BFD) is a peripheral vascular disease resulting in gangrene of the lower extremities. In the present work, the objective was to examine the amount of arsenic and mercury in urine of BFD patients. The urine specimens were acidified with nitric acid and digested in a microwave oven. A solid phase extraction (SPE) cartridge was used for sample purification and preconcentration. The analytical technique for the determination of arsenic was by hydride atomic absorption spectrophotometry (HAAS) and for mercury by cold vapor atomic absorption spectrophotometry (CVAAS). The sensitivity and accuracy of the analytical techniques were checked with Lanornorm control urine. Arsenic and mercury concentrations in the urine of normal controls and BFD patients were found to be 11.3±4.7 μg/1 and 33.6±23.1 μg/1 for As ; 5.0±1.8 μg/1 and 11.6±5.9 μg/1 for Hg, respectively. The life background of the BFD patients is also briefly mentioned.

An Evaluation of Possible Biases in the U.S. EPA’s Method 101A-Mercury Emissions from Stationary Sources

EPA Method 101A is used for the determination of particulate and gaseous mercury emissions from sewage sludge incinerators and other specified source. In this method, emissions are withdrawn isokinetically from the source and collected in acidic potassium permanganate solution. The mercury (Hg) collected in the mercuric form is reduced to elemental mercury and aerated from the solution into an optical cell and measured by cold vapor atomic absorption spectrophotometry (CVAAS)

Inductively coupled plasma mass spectrometry with direct injection nebulization for mercury analysis of drinking water

An improved technique has been developed to determine concentratlona of mercury in drlnklng water. Inductively coupkd pima maw spectrometry (ICPMS) with direct Injectlon nebullration (DIN) was used for the anslysls. A characterlzation was conducted and optknum operating parmeters found. The mercury detection lhnit with the DIN was comparable to a conventional pneumatk nebulizer (PN) whlk the Inherenl probkmr of memory effects were drastkaliy roducd. The edent of spectral Interference due to refractory oxtde formations was compared udng the DIN and the PN. Actual drlnklng water samples were spiked with varying concmtrationr of mercury and analyzed along with certified rdorence matarlak urlng DIN-ICPMS. Duplicate analysis wasconductedbetween theDIN-ICPMS and theconventbnai technique of cold vapor atomic absorption spectrophotometry (CVM) and a comparison made.

Factors Affecting Blood Mercury Concentrations in Practicing Dentists

It has been suggested that mercury vapor may be transformed into highly toxic organomercury compounds by micro-organisms in the oral cavity and gastrointestinal tract. If this hypothesis is correct, practicing dentists might be expected to have concentrations of organic mercury in their blood higher than that found in non-dentists. Blood mercury concentrations of practicing dentists and non-dentists were determined by means of cold-vapor atomic absorption spectrophotometry. Potential sources of mercury exposure were identified in both dentists and non-dentists through a questionnaire completed at the time of sampling. Concentrations of total and inorganic blood mercury were significantly higher in dentists than in non-dentists. The organomercury concentrations of the two groups were not statistically different (p greater than or equal to 0.05). The high concentration of inorganic mercury in the blood of dentists was not related to the organomercury level, suggesting that biotransformation of inorganic mercury to organomercury does not occur in vivo. However, the concentration of blood organomercury was positively correlated with the frequency of fish consumption. There was no correlation between the number of amalgam restorations and the concentration of inorganic blood mercury for both groups. Accidental mercury spills in the dental operatory may contribute most to the concentration of inorganic blood mercury in the blood of dentists.

Factors affecting the determination of total mercury in biological samples by continuous-flow cold vapor atomic absorption spectrophotometry.

The acidic reduction of Hg using a continuous-flow analytical system was evaluated. With 25% SnCl2 as the reductant, characteristic concentrations (sensitivities) of 0.44 microgram/L (open cell) and 0.29 microgram/L (flow-through cell) were obtained using inorganic Hg2+ standards in 1.5% HCl. When CH3Hg+ standards were used, absorption signals were an order of magnitude lower, indicating that Sn(II) is incapable of producing Hg degree from organic Hg in this acidic reduction system. Addition of CdCl2 to the SnCl2 reductant, as suggested by Magos (1) for the reduction of organomercurials under alkaline conditions, was without beneficial effect. Similarly, combining Sn with another reducing agent (hydroxylamine hydrochloride), or a strong alkaline solution (40% NaOH), in the reaction coil of the flow-through system did not significantly enhance the Hg absorption signal for either inorganic or organic Hg. Recovery of Hg from spiked liver homogenates digested at 70-80 degrees C using a HNO3/H2SO4/HCl procedure and stabilized with 0.5 mM K2Cr2O7 was > 85% using either inorganic Hg2+ or CH3Hg+, indicating that this digestion procedure successfully breaks the C-Hg bond to form readily reducible Hg species. Using L-cysteine to stabilize standards of inorganic Hg2+ in HCl caused significant depressions of the Hg absorption signal at L-cysteine concentrations > 0.001% (approximately 0.5 mM); 0.1% L-cysteine caused total suppression of the Hg signal. These results indicate that: (1) acidic reduction of Hg by Sn in this continuous-flow system requires breakdown of organomercurials prior to analysis; (2) tissue digestion using HNO3/H2SO4/HCl followed by the addition of K2Cr2O7 to stabilize Hg2+ achieves this breakdown and allows good recovery of total Hg; and (3) use of L-cysteine to complex and prevent losses of Hg should be avoided in systems using acidic reduction of Hg. Concentrations of endogenous tissue sulfhydryls are generally lower than those associated with depressed absorbance signals during the acidic reduction of Hg.

Determination of methylmercury in biological certified reference materials

Various isolation techniques (ion — exchange, extraction, volatilization, distillation) were used to separate organic Hg, followed by cold vapor atomic absorption spectrophotometry (CV AAS) for determination of total organic Hg, and/or gas chromatography (electron capture detector) for determination of McHg and EtHg if present. Some currently available CRMs with certified total Hg values, including NBS Oyster Tissue 1566, NBS Horse Kidney H-9, IAEA Fish Flesh Homogenate MA-A-2/TM, IAEA Fish Tissue Lyophilized MA-B-3/TM, IAEA Mussel Tissue MA-M-2/TM, IAEA Copepod Homogenate MA-A-1/TM, IAEA Shrimp Tissue Homogenate MA(S)-MEDPOL-86/TM, NIES No.5 Human Hair, and NIES No.9 Sargasso were investigated. CRMs from the National Research Council of Canada (TORT-1, DORM-1, DOLT-1) which have recently been certified for MeHg, were also analyzed. Results obtained by different approaches show good agreement. The advantage of GC which permits different organic compounds to be determined was demonstrated in the case of some IAEA CRMs where both McHg and EtHg was found; indirect CV AAS gives the results for total organic Hg. Therefore it can be suggested that various currently available CRMs for total Hg can also be used for establishment of recommended values for McHg (and EtHg if present) and organic Hg. However, additional intercalibration exercises or data from other laboratories are necessary to obtain a consensus.

The Effect of Tin on the Corrosion Behavior of the Ag-Hg Phase of Dental Amalgam and Dissolution of Mercury

The anodic polarization behavior of the Ag-Hg matrix phase of dental amalgam (gamma 1) and the rate of mercury dissolution were examined as a function of the tin content. The objectives were to determine the effect of tin on the electrochemical behavior and dissolution of mercury and to provide evidence on whether tin dissolves in the gamma 1 phase or precipitates as a tin-rich phase. Anodic polarization curves were recorded for specimens of the gamma 1 phase containing 0-1.5% Sn and for the gamma 2 phase and a gamma 2-containing dental amalgam, in synthetic saliva. Mercury dissolved in synthetic saliva in 24 h was determined for the gamma 1 phase containing 0-1.0% Sn, with cold-vapor Atomic Absorption Spectrophotometry used for mercury analysis. Tin induced passive behavior of the gamma 1 phase and suppressed mercury dissolution. The passive gamma 1 phase did not exhibit a breakdown of passivity occurring at the gamma 2 phase. The results were consistent with the tin presence in gamma 1 in a solid solution, rather than in tin-rich precipitates, and indicated that at least 1.5% Sn can be dissolved in gamma 1 at 37 degrees C.

The Release of Mercury from Dental Amalgam: The Mechanism and in vitro Testing

Dissolution of mercury from the Ag-Hg matrix phase of dental amalgam is distilled water and synthetic saliva, and the mercury evaporation from the solutions, were studied in vitro. The main objectives of the study were to evaluate the factors that affect the results of the mercury release tests, and to consider the possible mechanisms of the release in vivo. Specimens were exposed to the liquids in open or closed bottles, and the changes in the mercury concentration were determined by cold-vapor Atomic Absorption Spectrophotometry. Concentration vs. time tests showed the dissolution rate decreasing with time. Tests involving sequences of short and long exposures with solution changes showed higher average rates for short-term dissolution into the fresh solution than for the longer preceding exposures. The differences were attributed to a stifling effect of the concentration of elemental mercury on the dissolution. It is believed that mercury dissolved mainly in the elemental form and that a continuous increase in the concentration was made possible by oxidation in the solution. In open cells, some of the mercury was lost by evaporation. The analysis showed that the results of mercury dissolution tests depend on many test variables, such as time, solution volume, oxidation and evaporation conditions, etc. Evaporation, dissolution, and evaporation/dissolution mechanisms of the mercury release in vivo were considered. It was concluded that the dissolution/evaporation model best described the mercury release from dental amalgam restorations.

Mercury levels in the sediment, water, and selected finfishes of Laguna Lake, The Philippines

Monthly samples of sediment, water and commercially important species of fish, primarily Oreochromis niloticus and Chanos chanos, plus a few other species, were collected from the West Bay area of Laguna Lake, The Philippines from January to December 1987. Mercury levels were determined in all samples by cold vapor atomic absorption spectrophotometry. Results showed that sediment samples contained mercury levels ranging from 26.7 to 117 ppb. Mercury levels in water samples were low, ranging from below detectable to 0.5670 ppb. The mercury levels in the water were negatively correlated with conductivity and dissolved oxygen and positively correlated with turbidity. The mercury burden of the fish species samples was below the maximum permissible level set by the WHO and USFDA of 0.05 ppm. No direct correlation was observed between mercury levels in sediment and water, water and fish and sediment and fish.

Comparison of release of mercury from three dental amalgams

Mercury release from dental amalgams has generated considerable concern in recent years and is the subject of this study. Specimens of one admixed high-copper amalgam (Contour), one lathe-cut low-copper amalgam (SDI), and a new tin- and copper-free amalgam claimed to be non-mercury-releasing (Composil) were evaluated for release of mercury when incubated in purified water at 37°C. Measurement of mercury was done by cold-vapor atomic absorption spectrophotometry, and the amount released was expressed as μg/cm 2/24 hr. Study was conducted over a four-week period. Results show that Contour and SDI released similar insignificant amounts (mean release of < 0.1 μg/cm 2/24 hr) compared with Composil (mean release of 41.0 μg/cm 2/24 hr). The difference in release by Composil compared with that by Contour and SDI is highly significant (P < 0.001). The implications of chronic release of mercury from dental amalgams are discussed. Long-term release studies are in progress.