Hg Vapor Research Articles

Solid-Phase Microextraction Mediated Solid-Phase Dielectric Barrier Discharge Vapor Generation-Atomic Fluorescence Spectrometry for Sensitive Determination of Mercury in Seawater.

A novel method coupling solid-phase microextraction (SPME) to solid-phase dielectric barrier discharge (SPDBD) vapor generation was proposed and used for the sensitive detection of trace mercury (Hg) in seawater with atomic fluorescence spectrometry (AFS) in this work. The method proposed herein offers the unique advantages of integrating desorption and chemical vapor generation into one step, eliminating the use of elution reagents, and reducing the analysis time. SPME with multiwalled carbon nanotubes (MWCNTs) coated on the glass tube was used to extract Hg2+ in seawater. The Hg2+ was then desorbed and reduced to Hg0 vapor by SPDBD, which was detected by cold vapor AFS. The parameters affecting Hg2+ extraction, desorption, and vapor generation were studied. The detection limit of Hg2+ was 0.0003 μg L-1, and the relative standard deviation at a Hg2+ concentration of 0.05 μg L-1 was 4.4%. This method also has excellent antimatrix interference ability for Hg2+ determination with recoveries between 91.8% and 101.1% in the presence of extremely high concentrations (two million times excess) of coexisting ions. The practicality of this method was also evaluated by analyzing two different certified reference materials of Hg2+ in water and several seawater samples with good spike recoveries (94.0%-107.4%). Compared with solid-phase photothermo-induced vapor generation, this method has higher extraction efficiency and higher desorption efficiency without the assistance of heating as well as a lower detection limit of Hg2+, which is capable of performing trace Hg analysis in seawater.

Multielement electrochemical vapor generation system coupled with atomic fluorescence spectrometer for simultaneous measurement of trace levels of As and Hg in coastal seawater samples

BackgroundToxic elements As and Hg in coastal waters affect human health through the food chain even at trace levels. The simultaneous determination of As and Hg in seawater using electrochemical vapor generation (ECVG) with atomic fluorescence spectrometer (AFS) currently has technical bottlenecks. One is the need for a simple and efficient chemical reaction cell and corresponding parameters to generate both AsH3 and Hg vapors, and the other is a suitable preservation method of the mixed standard solutions. ResultsA novel, efficient, online ECVG device was developed and interfaced with a laboratory-built multichannel AFS. The electrolytic cell adopted Sn–Pb alloy as the cathode material to generate both AsH3 and Hg vapors by electrolysis, replacing the unstable reagent tetrahydroborate (THB) usually used in most traditional vapor generation methods. The AFS was equipped with a built-in H2 generator for fuel supply, instead of the conventional acid-THB system. A mixed standard solution of As and Hg was prepared and preserved using thiourea-ascorbic acid as a fixing agent for Hg and a prereduction agent for As(V). The method detection limits (LOD, 3σ) were 0.005 and 0.003 μg/L for As and Hg, respectively. The relative standard deviations (RSD, n = 8) of the spiked samples were 2.8 % (0.50 μg/L As) and 3.1 % (0.05 μg/L Hg), respectively. The recoveries of standard spiked seawater samples with different salinities ranged from 86.1 % to 115.3 %. SignificanceThe system has been successfully applied to the simultaneous analysis of As and Hg in the seawater samples collected from the Xiamen coastal area. The study results provide a sensitive, accurate, and efficient method to promote the development and utilization of simultaneous analysis of multielement in seawaters.

Mercury air, urine monitoring and health effects on occupationally exposed dental healthcare workers in Delhi, India.

Mercury (Hg) is a toxic heavy metal with multiple uses in various medical devices. Hg is used in dentistry as a restorative material. Such use creates significant exposure to dental practitioners. Hence, it is important to assess the risk created by Hg use in healthcare. To quantify airborne Hg vapour exposure and Hg levels in dental healthcare workers, and determine the association of various symptoms and diseases to Hg exposure. Air monitoring of Hg vapours were conducted in dental clinics and amalgam rooms. Urine samples were collected from occupationally exposed dental healthcare workers and urine Hg levels were measured. A cross-sectional health survey was conducted in 23 healthcare units of Delhi to determine an association between Hg exposure and various health effects. Hg vapour concentration ranged from 0.96μg/m3 to 15μg/m3, the highest concentration was recorded in the amalgam room (15μg/m3). Urine Hg levels in healthcare workers (0.51±0.17μg/L) were higher than the control (0.29±0.05μg/L). A cross-sectional health survey revealed a significant prevalence of confusion, forgetfulness, muscle spasm, and tremors by the respondents. Hg concentration in dental clinics may hover above the prescribed safe levels posing a definitive health risk to healthcare workers. Urinary Hg measurements did not reveal an excess of body burden except in one case. Since Hg bio accumulates, it is probable as these workers grow older, they may end up with a higher body burden of Hg that may lead to a variety of adverse health outcomes.

Co2+ - assisted continuous flow UV-induced Hg vapor generation coupled with a modified MSIS gas–liquid separator and microwave plasma atomic emission spectrometry

Co2+ - assisted continuous flow UV-induced Hg vapor generation coupled with a modified MSIS gas–liquid separator and microwave plasma atomic emission spectrometry

A miniaturized flow batch chemical vapor generation system for Hg determination in fish by ICP-MS

A new flow batch (FB) system for chemical vapor generation (CVG) is proposed for mercury (Hg) determination in fish. An inductively coupled plasma mass spectrometer was used as a detector. Low-cost peristaltic mini pumps were used to propel the solutions and different configurations of FB systems (reactor/gas/liquid separator) were studied. The proposed configuration of the FB-CVG system allows good sensitivity, low limit of detection (LOD) and low consumption of reagents and sample solutions. In summary, only 1 mL of reductant, 1 mL of acid and 0.16 mL of sample are needed. The proposed method has good linearity, precision (better than 5 %), LOD of 0.008 μg g−1 and LOQ of 0.012 μg g−1, and high sample throughput, allowing 90 measurements/h. The accuracy of the method was evaluated through the analysis of a certified reference material (DOLT-4 Dogfish Liver), whose result is in good agreement with certified value (t-test with 95 % confidence level) and the quantification limit meets current legislations, of 1.0 μg g−1 (Brazil) and 0.3 μg g−1 (EU). In addition, analyte recovery test was done, where Hg recovery was better than 95 %, demonstrating the good analytical performance of the method. To demonstrate the applicability of the method, five samples of fish tissue (muscle) were analyzed. The proposed FB-CVG system, in addition to being low cost, is robust and requires only the volume of reagents necessary for Hg vapor generation, producing a very low amount of waste. It can be concluded that the proposed system can be used for routine analysis for Hg determination in fish tissue. It is worth noting that with the appropriate adjustments, the system can be coupled to different Hg detectors.

Development and initial evaluation of a combustion-based sample introduction system for direct isotopic analysis of mercury in solid samples via multi-collector ICP-mass spectrometry

High-precision isotopic analysis of mercury (Hg) using multi-collector ICP-mass spectrometry (MC-ICP-MS) is a powerful method for obtaining insight into the sources, pathways and sinks of this toxic metal. Modification of a commercially available mercury analyzer (Teledyne Leeman Labs, Hydra IIc – originally designed for quantification of Hg through sample combustion, collection of the Hg vapor on a gold amalgamator, subsequent controlled release of Hg and detection using cold vapor atomic absorption spectrometry CVAAS) enabled the system to be used for the direct high-precision Hg isotopic analysis of solid samples using MC-ICP-MS – i.e., without previous sample digestion and subsequent dilution. The changes made to the mercury analyzer did not compromise its (simultaneous) use for Hg quantification via CVAAS. The Hg vapor was mixed with a Tl-containing aerosol produced via pneumatic nebulization, creating wet plasma conditions, and enabling the use of Tl as an internal standard for correction of instrumental mass discrimination. Accurate and precise (0.10 ‰ 2SD, δ202Hg, n = 5) results were obtained for an in-house standard solution of Hg (20 ng Hg sample intake). Initial validation relied on the successful analysis of two solid certified reference materials of biological origin (BCR CRM 464 Tuna fish and NRC-CNRC TORT-3 Lobster hepatopancreas). It was shown that instrumental mass discrimination can be adequately corrected for by relying on the use of an aqueous Hg standard solution (NIST SRM 3133), without the need of matrix-matching. The novel setup developed thus allows for direct high-precision isotopic analysis of Hg in solid samples, thus enhancing the sample throughput. It is also suited for samples for which low amounts are available only and/or that are characterized by low Hg concentrations.

Dental Metal Matrix Composites: The Effects of the Addition of Titanium Nanoparticle Particles on Dental Amalgam.

Dental amalgams have been used by dentists for the restoration of posterior human teeth. However, there have been concerns about the release of mercury from amalgams into the oral cavity. The objective of the present research is to study the effect of titanium (Ti) nanoparticles on the microstructural mechanism of the release of mercury vapor in two commonly used brands of dental amalgam (the Dispersalloy: 11.8% Cu; the Sybralloy: 33% Cu). Ti powder was added to both the Dispersalloy and the Sybralloy in increments of 10 mg up to 80 mg. The addition of Ti powder to both brands of dental amalgam has been found to result in a considerable decrease in Hg vapor release. The decrease in the Hg vapor release due to Ti addition has been explained by the formation of strong Hg-Ti covalent bonds, which reduce the availability of Hg atoms for evaporation. The Ti atoms in excess of the solubility limit of Ti in Hg reside in the grain boundaries, which also reduces the evaporation of Hg from the amalgam. The binding of Hg with Ti via a strong covalent bond also results in a significant improvement in mechanical properties such as Vickers hardness.

Efficient and selective capture of various mercury species from water using an exfoliated thiocellulose

The primary challenge in mercury (Hg) adsorbents for large-scale practical applications is to achieve the balance between performance and economy. This work attempts to address this issue by synthesizing an exfoliated thiocellulose (CU-SH) with high thiol density and hierarchical porosity using in-situ ligands grafting combined with chemical stripping. The prepared CU-SH shows remarkable physical stability and chemical resistance, and the micron sized fiber is conducive to separation from water. Hg(II) adsorption tests in water demonstrate that CU-SH has broad working pH range (1−12), fast kinetics (0.64 g/(mg‧min)), high adsorption capacity (652.9 mg/g), outstanding selectivity (Kd = 6.2 × 106 mg/L), and excellent reusability (R > 95 % after 20 cycles). Importantly, CU-SH exhibits good resistance to various coexisting ions and organic matter, and can efficiently remove Hg(II) from different real water. CU-SH can be made into a Point of Use (POU) device for continuous and efficient removal of Hg(II) from drinking water. 0.1 g CU-SH filled device can purify 3.2 L of Hg(II) (0.5 ppm) contaminated tap water before the breakthrough point of 2 ppb. Moreover, CU-SH also reveals good adsorption affinity for Hg-dissolved organic matter complexes (Hg(II)-DOM) in water, chloro(phenyl)mercury (PMC) in organic media and Hg0 vapor in air, suggesting the great practical potential of CU-SH.

Estimated mercury vapor exposure from amalgams among American pregnant women.

This study examined the impact of mercury (Hg) vapor exposure from amalgams among all American pregnant women. Amalgam-Hg vapor exposure among 1,665,890 weighted-pregnant women (n = 37) was examined in the 2015-2020 National Health and Nutrition Examination Survey (NHANES). Correlation coefficients between amalgam surfaces and daily micrograms (µg) of urinary Hg excretion and daily µg of Hg vapor exposure from amalgams per kilogram (Kg) bodyweight were calculated. Daily Hg vapor exposure from amalgams was compared to Hg vapor safety limits. About 600,000 pregnant women (∼36%) had at least one amalgam surface. Median daily urinary Hg excretion was ∼2.5-fold higher among pregnant women with amalgams as compared to pregnant women without amalgams. A significant correlation was observed between the number of amalgam surfaces and daily urinary Hg excretion. Among pregnant women with amalgams, it was estimated that the median daily Hg vapor dose from amalgams was 7.66 µg of Hg and 0.073 µg of Hg/Kg bodyweight. Among all pregnant women, ∼28% received daily Hg vapor doses from amalgams above the least restrictive United States (US) Environmental Protection Agency (EPA) safety limit and ∼36% received above the most restrictive California (CA) EPA safety limit. Given the potential for fetal toxicological effects from prenatal Hg vapor exposure, special emphasis needs to be placed on reducing/eliminating amalgams in pregnancy/women of reproductive age and future studies should evaluate adverse pregnancy outcomes.

Mercury Extraction from Multivitamin Mixtures Followed by Determination Using FI-CV-ICP-MS

This study deals with a method for Hg determination in multivitamin supplements. Mercury was extracted with L-cysteine prior to its determination using flow injection-cold vapor generationinductively coupled plasma-mass spectrometry. A miniaturized flow injection system was employed for Hg vapor generation and its introduction in the plasma whereas 1% (v v-1) HCl and 0.005% (m v-1) NaBH4 were used for that purpose. Mercury extraction was carried out using 6 mL of 1% m v-1 L-cysteine and 50 mg of sample. Accuracy was proved by comparing the Hg concentration found using L-cysteine with the Hg concentration found in the sample decomposed using microwave-assisted digestion, and analysis of certified soil. The limits of detection and quantification of the proposed method were 2 and 6 ng g-1 of Hg, respectively. The relative standard deviation was < 10% (n = 5). Five samples of multivitamin supplements were analyzed and, in any sample, the tolerable amount of Hg (4.0 µg kg-1 body weight) recommended by the World Health Organization was exceeded. The proposed method for Hg determination meets the current legislation and is feasible for Hg monitoring in multivitamin supplements.

Characterization of atmospheric mercury from mercury-added product manufacturing using passive air samplers

Although alternatives to mercury (Hg) are available in most products and industrial activities, Hg continues to be an ingredient in some products, including fluorescent lamps and electrical and electronic equipment (EEE). In this work, low-cost passive air samplers (PASs) were used to investigate the atmospheric Hg pollution in Zhongshan, a large industrial city and major hub of mercury-added product manufacturing in South China. The GEM concentrations in the atmosphere were measured for two weeks during the summer of 2019 at a total of 144 sites across Zhongshan. Comparison with the results of active sampling confirmed that the PASs yielded accurate and reliable gaseous elemental mercury (GEM) concentrations and were thus well-suited for multi-site field monitoring. The mean GEM concentrations in the areas with mercury-added product manufacturing activities (5.1 ± 0.4 ng m−3) were significantly higher than those in other parts of Zhongshan (1.5 ± 0.4 ng m−3), indicating that local releases, rather than regional transport, were responsible for the atmospheric Hg pollution. Elevated GEM concentrations (up to 11.4 ng m−3) were found in the vicinity of fluorescent lamp and EEE factories and workshops, indicating significant Hg vapor emissions, presumably from the outdated production technologies and non-standard operation by under-trained workers. The Hg emissions from mercury-added product manufacturing were estimated to be 0.06 and 7.8 t yr−1 for Zhongshan and China, respectively, based on the scales of fluorescent lamp and EEE production. The non-carcinogenic health risk of Zhongshan residents from inhalation and ingestion was judged acceptable, whereby the inhalation exposure in Hg-polluted areas exceeded that of dietary ingestion. These findings demonstrate that mercury-added product manufacturing still contributes notably to anthropogenic gaseous Hg releases in the industrial areas with intense mercury-added product manufacturing activities.

Deposition and Re-Emission of Atmospheric Elemental Mercury over the Tropical Forest Floor.

Significant knowledge gaps exist regarding the emission of elemental mercury (Hg0) from the tropical forest floor, which limit our understanding of the Hg mass budget in forest ecosystems. In this study, biogeochemical processes of Hg0 deposition to and evasion from soil in a Chinese tropical rainforest were investigated using Hg stable isotopic techniques. Our results showed a mean air-soil flux as deposition of -4.5 ± 2.1 ng m-2 h-1 in the dry season and as emission of +7.4 ± 1.2 ng m-2 h-1 in the rainy season. Hg re-emission, i.e., soil legacy Hg evasion, induces negative transitions of Δ199Hg and δ202Hg in the evaded Hg0 vapor, while direct atmospheric Hg0 deposition does not exhibit isotopic fractionation. Using an isotopic mass balance model, direct atmospheric Hg0 deposition to soil was estimated to be 48.6 ± 13.0 μg m-2 year-1. Soil Hg0 re-emission was estimated to be 69.5 ± 10.6 μg m-2 year-1, of which 63.0 ± 9.3 μg m-2 year-1 is from surface soil evasion and 6.5 ± 5.0 μg m-2 year-1 from soil pore gas diffusion. Combined with litterfall Hg deposition (∼34 μg m-2 year-1), we estimated a ∼12.6 μg m-2 year-1 net Hg0 sink in the tropical forest. The fast nutrient cycles in the tropical rainforests lead to a strong Hg0 re-emission and therefore a relatively weaker atmospheric Hg0 sink.

Graphene oxide/ZnO nanocomposites applied in photocatalysis of dyes: Tailoring aqueous stability of quantum dots

Nanocomposites between ZnO Quantum Dots (QDs) and Graphene Oxide (GO) were synthesized by sol-gel method in isopropanol. The proportion of GO aqueous dispersion was evaluated and ZnO QDs were also prepared with addition of water, for comparison. Indeed, the GO or water addition had a huge impact in the ZnO QDs size and photoluminescence, once the greater the GO/water addition, the greater the ZnO QDs size (from 4.5 ± 0.1–23.8 ± 0.4 nm) and the 50 µL of GO (or water) added to the synthesis led to a higher intensity emission. The photocatalytic activity of the ZnO-based materials was evaluated for methylene blue (MB) and astrazon blue (AB) degradation in isopropanol and water using two different sources of light irradiation (fluorescence and Hg vapor lamps). Once again, the GO/water addition affected their photocatalytic behavior and stability in aqueous medium. The ZnO QDs/GO had an impressive photocatalytic performance in both sources of light irradiation in isopropanol and aqueous medium (99% and 93% of degradation after 30 min of irradiation with Hg vapor lamp, respectively). In addition, the photocatalytic activity of this nanocomposite was stable when submitted up to 5 photodegradation cycles and to higher MB concentrations, besides being successfully reused in aqueous medium.

Absence of Genotoxic Effect of Mercury Vapor in Lymphocytes of Occupationally Exposed Individuals

Objective: to evaluate the genotoxic effects caused by exposure to Hg vapor in individuals with occupational exposure in a municipality in northern Brazil. Methods: Blood samples were collected from 70 individuals (38 exposed and 32 unexposed controls) in heparinized tubes. The comet assay and the micronucleus test were used to detect the occurrence of genotoxic effects. The results were statistically analyzed using the Shapiro-Wilk normality test, Student's T test and ANOVA. Non-parametric data were analyzed using the Mann-Whitney and Kruskal-Wallis tests. Spearman's test was used to assess the correlation between dependent variables. Mean, geometric mean and standard deviation (SD) were calculated. Results and Conclusions: The evaluation of genotoxicity revealed no difference in the frequency of DNA damage when the two groups, control and exposed, were compared, even considering confounding variables such as smoking and alcoholism, gender, age, time of exposure. In conclusion, our results indicate that exposure to Hg vapor (elemental form) did not produce detectable genotoxic changes in blood cells in vivo. Research Implications: Although no genotoxic effects were detected in blood cells from individuals exposed to mercury vapor, studies with cells that are in more direct contact with this source of contamination, such as oral and nasal epithelial cells, should be performed to confirm whether elemental form of Hg has no genotoxic effect.

Quantum-jump analysis of frequency up-conversion amplification without inversion in a four-level scheme

In this work, we use the quantum-jump approach to study light-matter interactions in a four-level scheme giving rise to frequency up-conversion amplification without inversion (AWI). The results obtained apply to the case of neutral Hg vapour where, recently, it has been reported AWI of a probe field in the UV regime, opening the way for lasing without inversion in this range of frequencies. We show that, in this scheme, the key element to obtain maximum amplification is the fulfillment of the three-photon resonance condition, which favors coherent evolution periods associated with the probe field gain. We also investigate the parameter values in order to optimize amplification. The present study extends the theoretical understanding of the underlying mechanisms involved in AWI.

Novel Platinum-Nickel Composite Trap for Simultaneous and Direct Determination of Mercury and Cadmium in Soil and Its Mechanism Study.

In this work, following a metal-ceramic heater (MCH) as an electrothermal vaporizer (ETV), a novel composite Pt/Ni trap based on platinizing the foamed nickel was first fabricated to trap Hg and Cd simultaneously. So, a solid sampling Hg-Cd analyzer was developed to simultaneously detect trace Hg and Cd in soil samples, mainly consisting of an MCH, a composite Pt/Ni trap, and an atomic fluorescence spectrometer (AFS). This small-size MCH-ETV system only consumes 100 W for the complete vaporization of Hg and Cd in soil matrices. The Pt/Ni trap fulfills the complete trapping of Hg and Cd following the solid sampling MCH-ETV system and then fast releases them by heating. It was proved that trapped and released Hg and Cd by the Pt/Ni trap are atomic species using X-ray photoelectron spectroscopy (XPS) and other approaches; specially, the effective cotrapping of Hg and Cd might be due to forming alloys of Hg + Pt and Cd + Ni on the Pt/Ni trap. Under the optimized conditions, the method detection limits (LODs) of Hg and Cd reached 0.4 μg/kg and 0.04 μg/kg for a 20 mg sample size, the relative standard deviations (RSDs) were within 12% and 8% for soil samples, respectively, and the recoveries ranged from 96% to 105%, indicating favorable analytical sensitivity, precision, and accuracy. The whole analysis time can be controlled within 5 min without the soil digestion process. The proposed Hg-Cd analyzer is thus suitable for rapid detection of Hg and Cd in soil samples with advantages such as simplicity, green, and safety. Further, the proposed solid sampling ETV-composite trap method has a promising application potential in the field and rapid detection for multielements.

Flow injection gas analysis (FIGA) for more sensitive determination of Hg by inductively coupled plasma optical emission spectrometry

Aiming at a more sensitive determination of Hg, inductively coupled plasma optical emission spectrometry (ICP OES) was combined with a microplasma-induced vapor generation system operated in a completely new manner, i.e., a flow injection gas analysis (FIGA) mode. In this approach, Hg vapors were accumulatively generated in a closed discharge chamber and after a certain accumulation time (10–120 s), very concentrated vapors were injected from the discharge chamber into an Ar carrier gas entering the ICP torch. This resulted in appearing a time-dependent analytical signal for Hg that was much higher than this acquired for conventional ICP OES with the pneumatic nebulization (PN). The proposed novel method outperformed traditional PN-ICP OES in terms of the detection limit (DL) for Hg, i.e., 0.035 μg L−1versus 5 μg L−1 (140-fold improvement), and measurement precision (2.5% versus 8.3%). Moreover, (FIGA)SAGD-ICP OES offered a 4 times lower DL of Hg than commonly used chemical vapor generation (CVG)-ICP OES (0.15 μg L−1). To validate the trueness of this newly developed method, a certified reference material (CRM) of fish muscle (ERM-BB422) as well as spiked post-leaching solutions of bottom sediment (MODAS-2) and soils were analyzed. An excellent agreement between obtained results and certified values was found (recovery within 97.7–104%), indicating the very good trueness of the FIGA in the more sensitive determination of Hg by ICP OES.

Effect of Iron Plaque on Gaseous Elemental Mercury Uptake, Translocation, and Volatilization by Paddy Rice.

Paddy rice is a typical wetland plant species, and mercury (Hg) accumulation in this rice has received much attention over the last two decades. The role of root iron plaque on rice Hg accumulation is not well understood. The effects of iron plaque on Hg0 uptake, translocation, and volatilization in rice seedlings were investigated under hydroponic conditions using different rice genotypes. After induction of iron plaque on rice roots with pretreatment solutions containing 0, 15 and 30mg Fe2+L-1, rice seedlings were transplanted into specially designed airtight culture chambers, where roots were separated from the aerial parts and exposed to saturated Hg0 vapor. The results showed the following: (1) There were significant differences in the amount of iron plaque formed on the rice roots among the three genotypes. (2) A significant correlation was observed between the concentrations of Hg and Fe in the iron plaque of the root surface for the three genotypes (R2 = 0.933, p < 0.01). (3) Iron plaque may act as a barrier for Hg0 behavior, i.e., inhibiting the process of Hg0 uptake and translocation from the rhizosphere.

Ultra-trace determination of mercury by platinum-coated tungsten coil trapping cold vapour atomic absorption spectrometry

ABSTRACT Within the scope of this study, a simple, highly sensitive and rapid trapping method for the determination of mercury (Hg) was developed. In this method, the surface of the tungsten coil (W-coil) was coated with platinum using the electrolytic deposition technique. Scanning electron microscopy–energy-dispersive X-ray analyses were performed to examine the surface morphology of Pt-coated W-coil. During the experiment, firstly, Hg vapour generated by tetrahydroborate, used as a reducing agent, was efficiently trapped on the Pt-coated W-coil at collection temperature in hydrochloric acid medium. Subsequently, Hg trapped on the surface of the Pt-coated W-coil was revolatilised by the effect of releasing-stage gases at the optimised releasing temperatures and transported to quartz T-tube atomiser. The experimental conditions have been optimised. Under the optimised conditions, a limit of detection (LOD) of 8.8 ng L−1 was obtained using three times the standard deviation of blank values using Pt-coated W-coil trap cold vapour atomic absorption spectrometry (CVAAS) system. The precision of the measurements was evaluated by relative standard deviation of 4.4%, which is obtained by 11 consecutive measurements of reagent blanks for a collection volume of 6.83 mL corresponding to 90 s collection. The enhancement factors for both LOD (3 s) and characteristic concentration (Co) were found to be 5.09 and 5.02 when compared with the regular CVAAS system without trap. The accuracy of the proposed method was evaluated by analysing BCR 146 R (Sewage sludge), RTC (Sandy Loam 7), ERM-BD151 (skimmed milk powder) and NIST 1641e (mercury in water) certified reference materials (CRMs). There was a good agreement between certified and found values for all CRMs. The results of the application of the developed method in seawater showed the spike recovery ranges from 94.2% to 102.4%.

Detection of Mercury Vapor in Selected Governmental Dental Health Care Centers in Al-Karkh- Baghdad

Almost all governmental centers in Iraq are still using mercury amalgam in spite of available alternatives; that make the initial assessment very important to assess the current situation. The survey included visiting (17) site within health centers in three locations in each (the room space, amalgam capsule containers and medical waste storage containers). (510) measurements (10 readings in each location) have been taken for every health care center in Al-Karkh side in Baghdad (10 general health centers, 7 specialists' center). Potential quantity of emitted mercury vapor has been measured using a portable mercury vapor detection device (TRACKER 3000 IP). Broad variability was noted in the concentration of Hg vapor emitted depending on the amount of empty capsules that were collected, opened or closed container, room area, number of chairs in the room and patients per day, number of full containers and applying environmental and health safety rules. 94.1 % of visited centers exceeded the lowest allowed occupational levels, 76.5 % recorded high concentrations exceeding Ceiling Limit Value while 94.1 % exceeded the Minimum Risk Level. The mercury vapour concentration in work space and the mercury vapour intake by inhalation of chronic daily exposure have linear relation. Mercury dental amalgam and its empty capsules in healthcare centers are a major source of emitting toxic mercury vapor causing chronic and acute exposure to population and for most dentists. Keywords: Mercury vapours; Occupational exposure limits; Dental Mercury Amalgam