Cold Vapor Atomic Fluorescence Spectrometer Research Articles

A novel catalytic oxidation process for removing elemental mercury by using diperiodatoargentate(III) in the catalysis of trace ruthenium(III)

A series of experiments were conducted at a bench scale reactor to investigate the effects of key influencing factors on the Hg0 removal from flue gas using the prepared diperiodatoargentate (III) (DPA) as an oxidant, trace ruthenium(III) as a catalyst, respectively. The experimental results showed that the average Hg0 removal efficiency reached to 87.5% under the optimal conditions in which the DPA concentration was 1.03 mmol/L, catalyst concentration was 2.0 μmol/L, reaction temperature was 40 °C and solution pH was 8.5. Meanwhile, it was found from the experiments that the high concentrations of SO2 and NO could inhibit the Hg0 removal due to the competition between Hg0 and SO2/NO, while the lower NO concentration exhibited a slight promotion for Hg0 removal. The evolutions of DPA(III) and Ru(III) before and after the reaction were characterized by an ultraviolet visible spectrophotometer (UV–vis), from which, the promotional mechanism of Ru(III) on Hg0 removal was analyzed. The spent solution was analyzed by a cold vapor atomic fluorescence spectrometer (CVAFS), which verified that Hg0 was oxidized into Hg2+ by the catalytic system of DPA(III)-Ru(III), and DPA was converted into Ag+.

Distribution and risk assessment of trace metals in multifarious matrices of Vembanad Lake system, Peninsular India

Trace metal contamination in aquatic ecosystems is of significant concern in countries like India having a recent industrial history. The present study mainly focuses on the spatial and temporal distribution, occurrence and toxicity of five trace metals (Hg, Cd, Zn, Cu and Pb) in water and sediment matrix of Vembanad Lake system (VLS), India. Mercury analysis was done by using Cold Vapor Atomic Fluorescence Spectrometer, and the other metals were analysed using Volta metric-Trace metal analyser. The spatial distribution of trace metals in the study area showed the following trends, Zn > Pb > Cu > Cd > Hg, Zn > Pb > Cu > Hg > Cd for surface water and bottom water respectively. Health risk assessment on human population associated with trace metals was also calculated to predict their health impacts on human through non-dietary exposure. The trace metals contamination in water and sediments of VLS are potential to cause cancer on human population associated with the system. Ecological risk indices showed that the northern portion of VLS is more contaminated with trace metal than the other part of the system.

Feature changes of mercury during the carbonation of FGD gypsum from different sources

Flue gas desulfurization gypsum (FGDG), as byproducts in power plants, is produced in large quantities. A novel technology to recycle FGDG in carbonation process has recently been found. However, the potential hazards to human health and to environment originated from heavy metals residual in FGDG have to be considered in the recycled process. In this study, six FGDG samples (denoted as S1-S6) from coal-fired power plants equipped with different FGD configurations were collected. Heavy metal contents in six original FGDG samples and in their corresponding solid products after carbonation were determined by ICP-OES and cold vapor atomic fluorescence spectrometer (CVAFS). As one of toxic heavy metals present in FGDG, Hg speciation variations induced by the carbonation process were focused on and they were confirmed by means of sequential chemical extraction (SCE) method. Original FGDG samples from six sources and their post-carbonation samples have different distribution of heavy metals, due to their FGD processes applied and byproduct compositions as well. Hg contents in all original FGDG samples exceed the 2nd grade of the Chinese National Standard (1 ug g−1), and a decrease in Hg contents for samples from WFGD process can be observed in their post-carbonation. Formation of carbonates and ammonia complex were responsible for the Hg speciation variations.

Optimization and measurement uncertainty estimation of hydride generation–cryogenic trapping–gas chromatography–cold vapor atomic fluorescence spectrometry for the determination of methylmercury in seawater

Abstract This technical note presents optimization results of hydride generation volatilization coupled with cryogenic trapping, separation by gas chromatography and detection by cold vapor atomic fluorescence spectrometer after pyrolysis. Method performance was compared with the reference ethylation method and results from a previous study. Using GUM/Eurachem guidelines, we estimated expanded relative standard uncertainty (k = 2) of both methods. Expanded relative standard uncertainty was 11.1%, 15.0% and 21.3% for hydride generation, and 15.8%, 18.2% and 19.3% for ethylation, at the highest (> 400 fM), middle (100–150 fM) and lowest (

Development and optimization of a method for detecting low mercury concentrations in humic-rich natural water samples using a CV-ICP-MS technique

In this study a method for the determination of low total mercury (THg) concentrations in humic-rich natural water samples using cold vapor technique coupled to an inductively coupled plasma mass spectrometer (CV-ICP-MS) was developed and optimized. Instrumental parameters of the CV-ICP-MS system were optimized using experimental design software and the amount of oxidizing agent, bromine monochloride (BrCl), adjusted so as to be sufficient for the high concentrations of dissolved organic carbon (16–113mg DOCL−1) present in the field samples analyzed in this study. Method performance was assessed using spike recovery tests and analyzing certified reference material (ERM-CA615, groundwater). The detection and quantification limits of the method were 0.7ngL−1 (3σ) and 2.2ngL−1 (10σ), respectively. The field samples were collected from eight peatland forest catchments located in eastern Finland, six of which had been harvested for a study into the potential consequences of forest harvesting on trace metal mobility. THg concentrations in unfiltered, undiluted natural water samples determined using the optimized CV-ICP-MS method were compared with concentrations determined by cold vapor atomic fluorescence spectrometer (CV-AFS) based on the EPA method 1631. The results obtained with the two different methods were in good agreement with each other (r2=0.98). The CV-ICP-MS method was found to be reliable for detecting low THg concentrations in humic-rich natural waters.

Direct analysis of environmental and biological samples for total mercury with comparison of sequential atomic absorption and fluorescence measurements from a single combustion event

A Direct Mercury Analyzer (DMA) based on sample combustion, concentration of mercury by amalgamation with gold, and cold vapor atomic absorption spectrometry (CVAAS) was coupled to a mercury-specific cold vapor atomic fluorescence spectrometer (CVAFS). The purpose was to evaluate combustion-AFS, a technique which is not commercially available, for low-level analysis of mercury in environmental and biological samples. The experimental setup allowed for comparison of dual measurements of mercury (AAS followed by AFS) for a single combustion event. The AFS instrument control program was modified to properly time capture of mercury from the DMA, avoiding deleterious combustion products from reaching its gold traps. Calibration was carried out using both aqueous solutions and solid reference materials. The absolute detection limits for mercury were 0.002 ng for AFS and 0.016 ng for AAS. Recoveries for reference materials ranged from 89% to 111%, and the precision was generally found to be <10% relative standard deviation (RSD). The two methods produced similar results for samples of hair, finger nails, coal, soil, leaves and food stuffs. However, for samples with mercury near the AAS detection limit (e.g., filter paper spotted with whole blood and segments of tree rings) the signal was still quantifiable with AFS, demonstrating the lower detection limit and greater sensitivity of AFS. This study shows that combustion-AFS is feasible for the direct analysis of low levels of mercury in solid samples that would otherwise require time-consuming and contamination-prone digestion.

Reaction of gaseous mercury with molecular iodine, atomic iodine, and iodine oxide radicals — Kinetics, product studies, and atmospheric implications

Mercury is present in the Earth’s atmosphere mainly in elemental form. The chemical transformation of mercury in the atmosphere may influence its bioaccumulation in the human food chain as well as its global cycling. We carried out the first kinetic and product studies of the reactions of gaseous mercury with molecular iodine, atomic iodine, and iodine oxide radicals at tropospheric pressure (~740 Torr) and 296 ± 2 K in air and in N2 (1 Torr = 133.322 4 Pa; 0 °C = 273.15 K). Atomic iodine was formed using UV photolysis of CH2I2. IO radicals were formed by the UV photolysis of CH2I2 in the presence of ozone The reaction kinetics were studied using absolute rate techniques with gas chromatographic and mass spectroscopic detection (GC–MS). The measured rate coefficient for the reaction of Hg0 with I2 was ≤ (1.27 ± 0.58) × 10–19 cm3 molecule–1 s–1. The reaction products were analyzed in the gas phase from the suspended aerosols and from deposits on the walls of the reaction chambers using six complementary methods involving chemical ionization and electron impact mass spectrometry, GC–MS, a MALDI-TOF mass spectrometer, a cold vapor atomic fluorescence spectrometer (CVAFS), and a high-resolution transmission electron microscope (HRTEM) coupled to an energy dispersive spectrometer (EDS). The major reaction products identified were HgI2, HgO, and HgIO or HgOI. The implications of the results are discussed with regards to both the chemistry of atmospheric mercury and its potential implications in the biogeochemical cycling of mercury.Key words: mercury, molecular iodine, atomic iodine, iodine oxide radicals kinetics, product study, atmospheric chemistry.

HEAVY METALS IN WILD BANANA PRAWN (FENNEROPENAEUS MERGUIENSIS DE MAN, 1888) FROM CHANTABURI AND TRAT PROVINCES, THAILAND

Concentrations of the heavy metals cadmium (Cd), mercury (Hg), nickel (Ni), lead (Pb), chromium (Cr), copper (Cu) and zinc (Zn) in adult banana prawns (Fenneropenaeus merguiensis de Man, 1888) were determined. Banana prawn samples were collected from two provinces of Thailand (Ampur LamSing, Chantaburi, and Ban Huanumkao, Trat) by gill net. Twenty five prawns from each province were randomly chosen from the catch and each prawn sample was divided into two parts: cephalothorax and abdominal muscle. Both parts were digested with concentrated nitric acid and hydrogen peroxide under pressure in a microwave digester. Hg levels were determined using a Cold Vapor Atomic Fluorescence Spectrometer. Cd, Cu, Cr, Ni, Pb, and Zn concentrations were determined using Atomic Absorption Spectrophotometer. Trace concentrations of Cd, Cu, Cr, Ni, Pb, and Zn in cephalothorax of banana prawns from both provinces were significantly higher (P < 0.05) than in muscle, with no significant difference observed for Hg. Concentrations of Hg, Cu, Zn, and Cd in banana prawns from Chantaburi province were significantly higher (P < 0.05) than those from Trat province. There was no significant difference observed between the contents of Pb, Ni, and Cr in banana prawns caught from the two provinces. Heavy metal content in banana prawn, especially in cephalothorax tissue, may be a good indicator (sentinel organism) of heavy metal contamination in the coastal environment. Mean concentrations of all heavy metals in abdominal muscle (edible part) were within the safety limits for human consumption. However, Cd and Cu concentrations in some of the cephalothorax samples from Chantaburi province were higher than the safety limits for human consumption. This suggests that a close monitoring program is needed to ensure the safety of F. merguiensis as a food source.

Product study of the gas-phase BrO-initiated oxidation of Hg0: evidence for stable Hg1+ compounds.

Mercury is a key toxic environmental pollutant, and its speciation affects its bioavailability. BrO radicals have been identified as key oxidants during mercury depletion events observed in Arctic and sub-Arctic regions. We report the first experimental product study of BrO-initiated oxidation of elemental mercury at atmospheric pressure of ca. 0.987 bar and T= 296+/-2 K. We used chemical ionization and electron impact mass spectrometry, gas chromatography coupled to a mass spectrometer, a MALDI-TOF mass spectrometer, a cold vapor atomic fluorescence spectrometer, and high-resolution transmission electron microscopy coupled to energy dispersive spectrometry. BrO radicals were formed using visible and UV photolysis of Br2 and CH2Br2 in the presence of ozone. We have analyzed the products in the gas phase, on suspended aerosols and on wall deposits, and identified HgBr, HgBrO/HgOBr, and HgO as reaction products. Mercury aerosols with a characteristic width of ca. 0.2 microm were observed as products. We herein discuss the implications of our results to the chemistry of atmospheric mercury and its potential implications in the biogeochemical cycling of mercury.

Coupling of the RP C18 preconcentration HPLC-UV-PCO-system with atomic fluorescence detection for the determination of methylmercury in sediment and biological tissue

An HPLC-UV-PCO-system (High Performance Liquid Chromatography, Ultraviolet, Post-Column Oxidation) was coupled with a cold vapor atomic fluorescence spectrometer (CVAFS) for separation and determination of mersalyl acid, methyl-, ethyl-, phenyl- and inorganic mercury. The mercury compounds were preseparated from the matrix using water vapor distillation. The compounds in the distillate were enriched as pyrrolidinedithiocarbamate complexes on an RP C18 preconcentration column and measured with the newly developed CVAFS detection system. The detection limit for methylmercury was 8 pg absolute for the enrichment of 5 mL distillate. The sensitivity of the HPLC-UV-PCO-CVAFS was improved by a factor of ten in comparison to a previously developed coupling technique with a cold vapor atomic absorption spectrometer (CVAAS). For methylmercury determination the detection limit for a 0.5 g sample was calculated to be 0.015 μg/kg.

Analyses of Organic and Inorganic Mercury by Atomic Fluorescence Spectrometry Using a Semiautomatic Analytical System

The present work describes an improved method for the determination of total and organic mercury by decreasing analysis time (use of a dual circuit), sample size, and handling procedures and eliminating the need for a clean room condition while maintaining the detection limit below the parts per trillion (pptr) level. Total mercury was analyzed after reduction by a one-stage gold amalgamation before transfer to an atomic fluorescence spectrometer. The detection limit was 0.07 ng L -1 for aqueous samples and 1 ng g -1 for biological tissue. Analysis time was 5 min. Organic mercury was first derivatized using sodium tetraethylborate and then trapped onto a graphitized carbon trap before transfer to an isothermally controlled GC column coupled to a cold vapor atomic fluorescence spectrometer