Cold Vapor Generation Atomic Fluorescence Research Articles

Assessment of total mercury in urban particulate matter by filter fiber assisted matrix solid-phase dispersion coupling with microplasma assisted-cold vapor generation

BackgroundThe evaluation of particle-bound mercury (PBM) exposure is a crucial aspect of assessing the global cycle of mercury (Hg) and its adverse effects on human health and ecosystems. Nevertheless, the precise and reliable measurement of PBM remains a formidable task because of the costly and cumbersome equipment required, as well as the inadequate sensitivities exhibited by current analytical techniques. In this study, we provide a unique and straightforward approach utilising filter fiber-assisted matrix solid-phase dispersion (FF-MSPD) in conjunction with single-drop solution electrode discharge-induced cold vapour generation atomic fluorescence spectrometry (SD-SEGD-CVG-AFS) for the precise quantification of PBM. The PBM contained in a small filter can be efficiently extracted with 200 μL of eluent (0.2% L-cysteine and 4% HCOOH) by FF-MSPD and subsequently converted to Hg0 using SD-SEGD-CVG, before being subjected to examination using AFS. ResultsThe resulted limit of detection (LOD, 3σ) was 0.17 pg m−3, obtained with a sample volume of 12 m3. This LOD is much higher than that of the techniques published in the literatures. The aforementioned technique was effectively utilised for the detection of mercury in 19 samples of PM2.5 and PM10 which were collected over a span of several months. Signiffcancen contrast to conventional methods, the proposed method offers a range of distinct advantages, including simplified operation, absence of memory effects, enhanced sensitivity, substantial reduction in reagent usage, and decreased secondary pollution. These advantages are particularly valuable for advancing research on the fate, transport, and exposure routes of environmental mercury.

Mercury Concentration in Liver Tissues of South American Fur Seals (Arctocephalus australis) from Southwestern Atlantic Ocean

Mercury (Hg) contamination of oceans is rapidly increasing, however Hg bioaccumulation in pinnipeds has been understudied. Here, we report for the first time Hg concentration in liver tissues of South American fur seals (Arctocephalus australis) in South and Southeast Brazil. Hg concentration was determined in twenty-five fur seals’ specimens found stranded along the coast of the Southwestern Atlantic Ocean. Samples were digested using the microwave technique and quantified by cold vapor generation atomic fluorescence spectrometry technique. The average Hg concentration was 6.37 mg kg-1 (wet weight), with a minimum concentration of 0.09 mg kg-1 and the highest concentration of 15.58 mg kg-1. No correlation between biological variables (sex, total length and weight) and Hg concentration in A. australis liver were found. The results presented here are of great importance to establish baselines for future evaluations of Hg contamination in marine mammals and the effects of this environmental problem in animal health.

Comparative elemental analysis of dairy milk and plant-based milk alternatives

Together with essential elements, toxic elements can also be found in food. In this study, we analysed the content of 41 elements in milk from mammals (cow, goat, and donkey) and plant-based milk alternatives (from soy, rice, oat, spelt, almond, coconut, hazelnut, walnut, cashew, hemp, and quinoa) using inductively coupled plasma mass spectrometry and cold vapour generation atomic fluorescence (for Hg). The analytical methods were validated using both milk certified reference materials and recovery experiments for different milk samples, obtaining satisfactory results in all cases. Only cow and goat milks were important sources of all major mineral elements like Ca, K, Mg, Na and P, and some minor elements like Se and Zn, while soy milk contained significant amounts of Cu and Fe, coconut milk contained Cr and Se, and hemp milk contained Mo. The level of toxic trace elements, including As, Cd, Hg, and Pb was very low in all analysed samples and did not pose any threat to consumers. The study is of significance for consumers of plant-based beverages from nutritional and food safety point of view.

Hybrid ionic liquid-3D graphene-Ni foam for on-line preconcentration and separation of Hg species in water with atomic fluorescence spectrometry detection

A preconcentration method based on a novel hybrid sorption nanomaterial consisting in a 3D graphene-Ni foam functionalized with an ionic liquid (IL) was developed for Hg species determination. The capability of different phosphonium-ionic liquids (PILs) to functionalize the hybrid material and form ion-pairs with Hg(II) chlorocomplex was evaluated. A comparative study with PILs containing the trihexyl(tetradecyl)phosphonium cation but different anions (dicyanamide and decanoate) and trihexyl(tetradecyl)phosphonium chloride was performed. Inorganic Hg (InHg) species was selectively retained forming a chlorocomplex (HgCl42−) followed by its retention in a column filled with the IL-3D graphene-Ni foam material implemented in an on-line micro solid phase extraction system (μSPE). The elution of Hg from the column was performed with SnCl2, which was also used as reducing agent for subsequent detection by cold vapor generation atomic fluorescence spectrometry (CV-AFS). Organic mercury species (OrgHg) were not retained on the sorption material of the column. The effect of several parameters determining the efficiency of the preconcentration and detection system (sample loading and elution flow rate, sample volume, instrumental conditions, etc.) was investigated. A sensitivity enhancement factor (EF) of 180 was achieved for InHg. The detection limit obtained after the preconcentration of 100 mL of sample was 3.6 ng L−1 of InHg. The relative standard deviation (RSD) was 4.1% (at 1 μg L−1 InHg and n = 10) calculated from the peak height of the absorbance signals (Gaussian form and reproducible peaks). This work reports the first application of the IL-3D graphene-Ni foam in an on-line μSPE preconcentration system for the speciation analysis of Hg in mineral, tap, and river water samples.

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

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

Green preparation of CuI particles in dielectric barrier discharge for colorimetric determination of trace mercury in comparison with atomic fluorescence spectrometric determination

The present work describes a solution-free method for preparation of copper(I) iodide (CuI) particles on copper wire by dielectric barrier discharge (DBD). The prepared material was applied to develop a colorimetric semi-quantitative analysis for fast screening analysis of trace mercury (Hg) by combing mercury vapor generation with Hg/CuI chromogenic reaction. Under the optimized conditions, the proposed method was successfully explored for visual determination of trace Hg in natural water and certified reference samples, and the results were in good agreement with cold vapor generation-atomic fluorescence spectrometry (CVG-AFS). It was proved to be a green, fast, visual and portable method for the determination of trace Hg in these real samples. It is a potential field analytical method for fast screening analysis.

Label-Free and Separation-Free Atomic Fluorescence Spectrometry-Based Bioassay: Sensitive Determination of Single-Strand DNA, Protein, and Double-Strand DNA.

Based on selective and sensitive determination of Hg(2+) released from mercury complex by cold vapor generation (CVG) atomic fluorescence spectrometry (AFS) using SnCl2 as a reductant, a novel label-free and separation-free strategy was proposed for DNA and protein bioassay. To construct the DNA bioassay platform, an Hg(2+)-mediated molecular beacon (hairpin) without labeling but possessing several thymine (T) bases at both ends was employed as the probe. It is well-known that Hg(2+) could trigger the formation of the hairpin structure through T-Hg(2+)-T connection. In the presence of a specific target, the hairpin structure could be broken and the captured Hg(2+) was released. Interestingly, it was found that SnCl2 could selectively reduce only free Hg(2+) to Hg(0) vapor in the presence of T-Hg(2+)-T complex, which could be separated from sample matrices for sensitive AFS detection. Three different types of analyte, namely, single-strand DNA (ssDNA), protein, and double-strand DNA (dsDNA), were investigated as the target analytes. Under the optimized conditions, this bioassay provided high sensitivity for ssDNA, protein, and dsDNA determination with the limits of detection as low as 0.2, 0.08, and 0.3 nM and the linear dynamic ranges of 10-150, 5-175, and 1-250 nM, respectively. The analytical performance for these analytes compares favorably with those by previously reported methods, demonstrating the potential usefulness and versatility of this new AFS-based bioassay. Moreover, the bioassay retains advantages of simplicity, cost-effectiveness, and sensitivity compared to most of the conventional methods.

Concentration and distribution of mercury in drainage catchment sediment and alluvial soil of China

The China Geochemical Baselines (CGB) project provides nation-wide catchment sediment/alluvial soil geochemical baseline data for 76 elements including Hg from 3382 top (0–25cm) and 3380 deep sediment/alluvial soil samples (under a depth of 100cm) at 3382 sampling sites, corresponding to a sampling density of about 1 site per 3000km2. Mercury was determined by cold vapour generation atomic fluorescence spectrometry (AFS) under strict quality control using field duplicates, standard reference materials and analytical replicate samples. The 25th percentile is at 13 and 11μg/kg in top and deep sediment/alluvial soil samples, respectively; these concentrations are close to the crustal abundance in China. The median Hg value is at 26 and 18μg/kg in top and deep sediment/alluvial soil samples, respectively; the 75th percentile is 56μg/kg in top and 36μg/kg in deep sediment/alluvial soil samples. Mercury concentrations at the 50th (26μgHg/kg) and 75th (56μgHg/kg) percentiles exhibit systematic enrichment in the near-surface material. The Hg distribution maps show distinct increasing trends from northern to southern and from western to eastern China, which are primarily related to the distribution of parent rocks, including rocks associated with mineral resources of Hg, Sb, Au, As, Pb–Zn, and climate, resulting in different soil types, as well as to population density with accompanying industrial development. Anomalous Hg concentrations in top sediment/alluvial soil samples above the 85th percentile (87μg/kg) occur mainly in south and south-west and sparsely in north and east China; they most likely have a dual origin, natural and human-induced, with the latter having a greater contribution because of the intense industrial activities, and particularly mercury emissions from Hg, Sb, As, Au, Pb–Zn mining, coal combustion, and production of batteries, fluorescent lamps, thermometers and cement. The spatial distribution map of Hg ratios of top to deep sediment/alluvial soil samples displays higher values, suggesting that top samples are most likely polluted from human activities in the highly populated urban areas of eastern China. About 6.86% and 3.52% of top and deep sediment/alluvial soil samples, respectively, have Hg concentrations higher than the soil contamination limit of 150μg/kg set by the National Environmental Standards for Heavy Metals of the People's Republic of China.

Observation of a physical matrix effect during cold vapour generation measurement of mercury in emissions samples

The observation of a physical matrix effect during the cold vapour generation–atomic fluorescence measurement of mercury in emissions samples is reported. The effect is as a result of the different efficiencies of liberation of reduced mercury from solution as the matrix of the solution under test varies. The result of this is that peak area to peak height ratios decease as matrix concentration increases, passing through a minimum, before the ratio then increases as matrix concentration further increases. In the test matrices examined – acidified potassium dichromate and sodium chloride solutions – the possible biases caused by differences between the calibration standard matrix and the test sample matrix were as large as 2.8% (relative) representing peak area to peak height ratios for calibration standards and matrix samples of 45 and 43.75, respectively. For the system considered there is a good correlation between the density of the matrix and point of optimum liberation of dissolved mercury for both matrix types. Several methods employing matrix matching and mathematical correction to overcome the bias are presented and their relative merits discussed; the most promising being the use of peak area, rather than peak height, for quantification.

Magnetic solid-phase extraction combined with in situ slurry cold vapor generation atomic fluorescence spectrometry for preconcentration and determination of ultratrace mercury

A magnetic SPE method combined with CVG-AFS for the determination of Hg2+is established.

Microwave Photochemical Reactor for the Online Oxidative Decomposition of p-Hydroxymercurybenzoate (pHMB)-Tagged Proteins and Their Determination by Cold Vapor Generation-Atomic Fluorescence Detection

A novel method is presented for the characterization and determination of thiolic proteins. After the labeling with p-hydroxymercurybenzoate, the pHMB-labeled proteins underwent on-line oxidation with a novel microwave (MW)/UV photochemical reactor, followed by cold vapor generation-atomic fluorescence spectrometry (CVG-AFS) detection. The MW/UV process led to the conversion of pHMB to Hg(II) with a yield of 89.0 ± 0.5% without using chemical oxidizing reagents and avoiding the use of toxic carcinogenic compounds. Hg(II) was reduced to Hg(0) in a knotted reaction coil with NaBH4 solution, stripped from the solution by an argon flow and detected. The chromatographic method for labeled thiolic peptides was linear in the 0.2-100 μmol L(-1) range, with a LOD as mercury of 57 nmol L(-1). This system has proven to be a useful interface for liquid chromatography coupled with CVG-AFS in the determination and characterization of thiolic proteins. This method has been applied to the determination of thiolic peptides after tryptic digestion of serum albumins from different species (human, bovine, rat, horse, and sheep).

Determination of thiomersal by flow injection coupled with microwave-assisted photochemical online oxidative decomposition of organic mercury and cold vapor atomic fluorescence spectroscopy

We developed a flow injection (FI) method for the determination of thiomersal (sodium ethylmercurithiosalicylate, C9H9HgNaO2S) based on the UV/microwave (MW) photochemical, online oxidation of organic mercury, followed by cold vapor generation atomic fluorescence spectrometry (CVG-AFS) detection. Thiomersal was quantitatively converted in the MW/UV process to Hg(II), with a yield of 97±3%. This reaction was followed by the reduction of Hg(II) to Hg(0) performed in a knotted reaction coil with NaBH4 solution, and AFS detection in an Ar/H2 miniaturized flame. The method was linear in the 0.01–2μgmL−1 range, with a LOD of 0.003μgmL−1. This method has been applied to the determination of thiomersal in ophthalmic solutions, with recoveries ranging between 97% and 101%. We found a mercury concentration in commercial ophthalmic solutions ranging between 7.5 and 59.0μgmL−1.

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

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

Evaluation of different extraction procedures for determination of organic Mercury species in petroleum by high performance liquid chromatography coupled with cold vapor atomic fluorescence spectrometry

An extraction procedure for extracting organic mercury species including methylmercury (MeHg) and ethylmercury (EtHg) from petroleum samples was developed. Three extraction methods (shaking, ultrasonic and microwave assisted extraction) using different extraction solvents (TMAH, KOH/CH3OH, HCl and acidic CuSO4/KBr) were investigated by comparing the extraction efficiency of the organic mercury species. Microwave assisted extraction at 60W for 5min using TMAH (tetramethylammonium hydroxide, 25%, m/v) provided the most satisfactory extraction efficiency for MeHg and EtHg in petroleum at 86.7%±3.4% and 70.6%±5.9%, respectively. Speciation analysis of mercury was done by on-line coupling of high performance liquid chromatography with cold vapor generation atomic fluorescence spectrometry (HPLC-CV-AFS). The proposed method was successfully applied to analyze several crude oil and light oil samples. The concentrations of MeHg ranged from under detection limit to 0.515ngg−1, whereas EtHg was not detected in the samples. This method can be a very useful tool in evaluating the risk of mercury emissions from petroleum.

Physico-chemical characterization of protein–pigment interactions in tempera paint reconstructions: casein/cinnabar and albumin/cinnabar

In this work, we characterized paint reconstructions using ovalbumin and casein as binders, and cinnabar (HgS) as a pigment, before and after artificial ageing. Egg and casein are common paint binders that were used historically in the technique of tempera painting. Despite extensive research on the identification of proteinaceous binders in paintings, there is a substantial lack of knowledge regarding the ageing pathway of their protein content, and their chemical interaction with inorganic pigments. Thermogravimetric analysis, infrared spectroscopy and size-exclusion chromatography (SEC) were used to reveal the physico-chemical processes involved in the ageing of proteins in paintings. Taken together, the three techniques highlighted that proteins are subject to both cross-linking and hydrolysis upon ageing, and to a lesser extent, to oxidation of the side chains. Mercury-protein interactions were also revealed using a cold vapour generation atomic fluorescence spectrometer mercury-specific detector coupled to SEC. The study clearly showed that HgS forms stable complexes with proteins and acts as a sensitizer in cross-linking, hydrolysis and oxidation.

Determination of Methylmercury and Inorganic Mercury in Sediments by High Performance Liquid Chromatography Hyphenated to Cold Vapor Generation Atomic Fluorescence Spectrometry Following a Microwave-Assisted Extraction

A high performance liquid chromatography(HPLC) coupled with cold vapor generation atomic fluorescence spectrometry method(CVAFS) has been developed for the separation and determination of methylmercury(MeHg+) and inorganic mercury(Hg2+) in sediment samples.The previous extraction of samples was carried out at a temperature of 80 ℃ for 8 min by using 0.1%(V/V) 2-mercaptoethanol as the extractant.The separation and determination of mercury species were achieved by direct injecting the extractant to HPLC-CVAFS system.Under the optimized conditions,the limit of detection was 0.58 ng/g for MeHg+ and 0.48 ng/g for Hg2+.The average recoveries were 96.2% and 95.8% for MeHg+ and Hg2+,respectively,by spiking three concentration levels of mercury species into samples.The proposed method was validated for the determination of certified reference material IAEA-405 and ERM-CC580,and the analytical results were in good agreement with the certified values.The proposed method was simple,rapid,accurate,no interference and suitable for the determination of methylmercury and inorganic mercury in sediment samples.

Microwave-Assisted Photochemical Reactor for the Online Oxidative Decomposition and Determination of p-Hydroxymercurybenzoate and Its Thiolic Complexes by Cold Vapor Generation Atomic Fluorescence Detection

We developed a photochemical method for the online oxidation of p-hydroxymercurybenzoate (PHMB), an organic mercury species widely used for mercaptan and thiolic compound labeling. The method is based on a fully integrated online UV/microwave (MW) photochemical reactor for the digestion of PHMB, followed by cold vapor generation atomic fluorescence spectrometry (CVG-AFS) detection. The MW/UV process led to the quantitative conversion of PHMB and thiol-PHMB complexes to Hg(II), with a yield between 91% and 98%, without using chemical oxidizing reagents and avoiding the use of toxic carcinogenic compounds. This reaction was followed by the reduction of Hg(II) to Hg(0), performed in a knitted reaction coil with NaBH(4) solution, and AFS detection in an Ar/H(2) miniaturized flame. The low MW power applied (18 W) allowed us to keep constant the temperature of the photochemical reactor (21 ± 1 °C), using a flowing water bath. This avoided peak widening due to diffusion processes generally occurring at high temperatures and in the additional cooling coil. This method has been applied to the determination of thiols in human plasma, blood, and wine.

Continuous flow electrolytic cold vapor generation atomic fluorescence spectrometric determination of Hg in water samples

The determination of trace concentrations of Hg in water samples by the use of electrolytic cold vapor generation (ECVG) system and AFS was studied. Several buffer solutions were used and the detection limits with these systems were found to be by a factor of 1–2 lower than in the conventional electrolytic cold vapor generation system. Comparing with the traditional inorganic acid, phosphate buffer solution (PBS) increased the signal intensity of Hg vapor from electrolytic generation on Pt cathode and reduced the impact of cathode erosion on the stability of signal intensity. Moreover, buffer solution has better interference tolerance. The effects of the electrolytic conditions and interference ions on the ECVG have been studied. Under optimized conditions and with PBS as catholyte the detection limit for Hg was found to be 0.27 ng L −1. The relative standard deviation was 2.8% for 11 consecutive measurements of 1 μg L −1 Hg. This method has been applied in the determination of inorganic Hg in Yangtze River water.

Determination of mercury by electrochemical cold vapor generation atomic fluorescence spectrometry using polyaniline modified graphite electrode as cathode

An electrochemical cold vapor generation system with polyaniline modified graphite electrode as cathode material was developed for Hg (II) determination by coupling with atomic fluorescence spectrometry. This electrochemical cold vapor generation system with polyaniline/graphite electrode exhibited higher sensitivity; excellent stability and lower memory effect compared with graphite electrode electrochemical cold vapor generation system. The relative standard deviation was 2.7% for eleven consecutive measurements of 2 ng mL − 1 Hg (II) standard solution and the mercury limit of detection for the sample blank solution was 1.3 рg mL − 1 (3σ). The accuracy of the method was evaluated through analysis of the reference materials GBW09101 (Human hair) and GBW 08517 (Laminaria Japonica Aresch) and the proposed method was successfully applied to the analysis of human hairs.

The determination of low-molecular-mass thiols with 4-(hydroxymercuric)benzoic acid as a tag using HPLC coupled online with UV/HCOOH-induced cold vapor generation AFS

An alternative analytical method was established for simultaneous determination of main urinary low-molecular-mass (LMM) thiols including cysteine (Cys), cysteinylglycine (Cys–Gly), homocysteine (HCys), γ-glutamyl cysteine (γ-Glu–Cys) and glutathione (GSH) as well as N-acetylcysteine (NAC) using RPLC coupled on line with UV/HCOOH-induced cold vapor generation atomic fluorescence spectrometry (UV/HCOOH–CVG–AFS) with 4-(hydroxymercuric)benzoic acid (PHMB) as a tag. The LMM thiols were stabilized and labeled by PHMB allowing the determination of reduced form thiols (R-thiols) and total thiols (T-thiols) without and with Tris-(2-carboxyethyl)-phosphine reduction. UV/HCOOH-induced Hg cold vapor generation was used instead of K 2SO 8–KBH 4/NaOH–HCl and/or KBrO 3/KBr–KBH 4/NaOH–HCl systems as an effective interface between RPLC and CVG–AFS. The limits of detection (3 σ) of RPLC–(UV/HCOOH)–CVG–AFS with PHMB labeling for Cys, HCys, Cys–Gly, γ-Glu–Cys and GSH as well as NAC were 4.6, 5.9, 5.9, 8.1, 7.3 and 5.9 nM with the RSD of 4.4, 5.1, 3.6, 7.5 4.2 and 3.7% ( n = 6 at 2 μM), respectively, satisfying the simultaneous determination of the main urinary LMM thiols. This developed method was applied successfully to determine the LMM R-thiols and T-thiols in 10 urine samples contributed by 10 healthy volunteers.