Vapor Generation Atomic Fluorescence Spectrometry 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.

Determination of trace tellurium by photochemical vapor generation-atomic fluorescence spectrometry using bifunctional Co-MOF-74 for preconcentration and sensitization.

The determination of trace tellurium in real samples with complicated matrix can be rather challenging due to the low abundance and interferences. Herein, we report a new method for the highly sensitive detection of Te(IV) by photochemical vapor generation-atomic fluorescence spectrometry (PVG-AFS), utilizing Co-MOF-74 as an adsorbent and a precursor of Co2+ ion sensitizer for preconcentration and enhanced PVG efficiency. The synthesized Co-MOF-74 can completely adsorb Te(IV) within 10min in a wide pH range. Following filtration and re-suspension in a dilute solution of formic and acetic acid, the adsorbed Te(IV) was converted to volatile compounds under the UV irradiation and swept to AFS for detection. A limit of detection of 0.08ng/mL for Te(IV) was obtained after a 50-fold preconcentration. The proposed method was used for analysis of various natural water samples for trace Te(IV), with satisfactory spike recoveries achieved.

A label-free strategy for H2O2 assay by chemical vapor generation-atomic fluorescence spectrometry

Hydrogen peroxide (H2O2) plays an essential role as a signal molecule in regulating diverse biological processes. It is of practical significance for accurately detecting the concentration of H2O2. In this work, a simple and label-free method was developed for H2O2 assay by chemical vapor generation-atomic fluorescence spectrometry (CVG-AFS). The assay was based on the phenomenon that l-Cysteine (l-Cys) can inhibit the AFS signal of As(III), while l-Cys can be oxidized to cystine by H2O2 and I-. Therefore, the concentration of H2O2 was proportion to the AFS signal. Under the optimal experimental conditions, a good linear range from 50 μM-4 mM was obtained, and the limit of detection (LODs) and relative standard deviation (RSD, n = 7) were calculated to be 9.9 μM and 0.4%, respectively. The proposed method has been successfully applied for H2O2 assay in medical disinfectants with good recoveries. It has the advantages of simple and cost-effective.

Multi-commutated flow system for inorganic selenium speciation in infusion tea samples by chemical vapor generation atomic fluorescence spectrometry

This work proposes an automated strategy for the inorganic selenium speciation in infusion tea samples, employing an MSFIA-CVG-AFS system and sodium tetrahydroborate for chemical vapor generation. The selenium total is determined after an online prereduction step of selenium (VI) to selenium (IV) in alkaline media, using a UV reactor with a 15 W Hg lamp. Selenium (IV) is quantified directly on the sample, and selenium (VI) is determined by the difference between the total selenium and selenium (IV) concentrations. The optimization of the chemical parameters: hydrochloric acid – hydrobromide acid solution concentration, potassium iodide concentration, sodium hydroxide concentration, and sodium tetrahydroborate concentration was performed using a (24−1) two-level fractional factorial design. The validation parameters were determined for total selenium and selenium (IV), and the results found were: limits of detection and quantification of 0.05 and 0.18 μg L−1, respectively; a linear range of 0.18–5.0 μg L−1, precision expressed as the relative standard deviation of 2.1% for a sample number of 10, for both analytes. The system allows the speciation analysis with an injection throughput of 15 injections per hour. This analytical method was applied for inorganic selenium speciation in nine infusions of tea samples purchased commercially in supermarkets in Palma de Mallorca City, Spain. The concentrations of selenium (IV) and total selenium varied from 0.2 to 0.6 μg L−1 and 0.4–2.0 μg L−1, respectively. The accuracy method was evaluated using spike tests, and the recoveries achieved varied from 91 to 111%.

One Fe3O4, two birds: Preconcentration and enhanced photochemical vapor generation for the determination of bismuth by atomic fluorescence spectrometry

Fe3O4 was served as an adsorbent and photocatalyst simultaneously in this work, Bi(III) was preconcentrated by Fe3O4 before its photochemical vapor generation-atomic fluorescence spectrometry (PVG-AFS) determination. The experimental conditions including the concentration of formic and acetic acid mixed solution, ultraviolet (UV) irradiation time, the concentration of Fe3O4 and the interferences from the common co-existing ions were explored. The AFS intensity was enhanced slightly by the mixed acid solution (30% (v/v) acetic acid + 5% (v/v) formic acid), while a significant enhancement was observed by using Fe3O4 as photocatalyst with the presence of mixed acid solution, 13-fold enhancement was obtained. The potential enhanced mechanism of Fe3O4 was also discussed here. Fe3O4 was decomposed in the mixed acid solution, Fe3+ was generated and further served as a sensitizer for improving Bi(III) efficiency. Under the optimized conditions, the limit of detection (LOD) of the proposed PVG-AFS system without or with preconcentration (sample of 5 mL) were 0.44 ng/mL and 0.07 ng/mL, respectively. This PVG-AFS system was successfully applied to the determination of four water samples and their spiked samples, with good recoveries ranging from 94% to 104%, demonstrating a good accuracy and applicability.

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.

A novel and indirect method for L-cysteine detection in traditional Chinese medicines by chemical vapor generation-atomic fluorescence spectrometry

L-Cysteine (L-Cys) is one of the material bases for the sweet taste of traditional Chinese medicines (TCMs), as well as the material basis for the pharmacological activity of TCMs in the treatment of diseases. Therefore, the rapid and accurate determination of the concentration of L-Cys has a certain significance for the quality evaluation of TCMs. In this work, a simple method was developed for label-free and indirect detection of L-Cys by chemical vapor generation-atomic fluorescence spectrometry (CVG-AFS) based on the phenomenon that L-Cys can inhibit the CVG of arsenic ion (As(III)). Therefore, the AFS signal is inversely proportional to the concentration of L-Cys. The effects of the concentration of hydrochloric acid (HCl) and potassium borohydride (KBH4) in the CVG process and the reaction time between L-Cys and As(III) have been investigated. Under the optimal experimental conditions, it shows a good linearity in the concentration range of 2–18 mM. The limit of detection (LOD) of the presented method is 2.8 μM, with a relative standard deviation (RSD) of 0.5%. The method has been successfully applied in the analysis of L-Cys in several animal TCMs with good recoveries.

Ivy extract-assisted photochemical vapor generation for sensitive determination of mercury by atomic fluorescence spectrometry

Making use of the natural plant extract as assistant matrix or photocatalyst provides an efficient strategy to break the limitation of traditional photochemical vapor generation atomic fluorescence spectrometry in efficiency, sensitivity, and biocompatibility. In this work, ivy extract-assisted photochemical vapor generation was proposed for the determination of trace mercury in natural water by atomic fluorescence spectrometry. The influencing factors such as irradiation time, irradiation wavelength and concentration of extract were systematically studied. Under the optimized experimental conditions, the limit of detection for total mercury was 0.03 ng mL−1 which is better than the ethanol- assisted photochemical vapor generation system. This method is green and sensitive, reduces the biological toxicity of photocatalytic materials and secondary pollution in the reduction process, and provides experimental basis for expanding the photochemical vapor generation system.

Filter-Assisted Separation of Multiple Nanomaterials: Mechanism and Application in Atomic/Mass Spectrometry/Fluorescence Label-Free Multimode Bioassays.

Atomic spectrometry (AS) has been widely used in bioassay, but it requires steps to immobilize or separate the signal molecules. In this work, based on the phenomenon that the filter membrane can selectively separate multiple nanomaterials (nanoparticles (NPs) and quantum dots (QDs)) and its related ions, including poly(thymine)-templated Cu NPs and free Cu2+, Ag NPs and free Ag+, CdTe QDs and Cd2+, we constructed multimode and label-free biosensors by chemical vapor generation-atomic fluorescence spectrometry (CVG-AFS), inductively coupled plasma mass spectrometry (ICP-MS), and fluorescence. In this strategy, terminal deoxynucleotidyl transferase (TdT) and polynucleotide kinase (PNK), H2O2, and mucin 1 can be sensitively detected using Cu2+, Ag+, and Cd2+ as the signal probe, respectively. As a result, TdT and T4 PNK in single cells level can be accurately quantified. In addition, the possible separation mechanism of filter membrane was proposed, both Donnan repulsion by charged functional layer and entrapment effect by nanomaterials size contributed to the outstanding separation performance. Subsequently, on the basis that CdTe QDs can selectively identify Cu NPs/Cu2+, Ag NPs/Ag+, and C-Ag+-C/Ag+, cation-exchange reaction (CER) was introduced in this platform due to its unique advantages, including improving the sensitivity of the above system (an order of magnitude), converting the non-CVG metal elements into CVG elements, and using low-cost AFS to substitute the high-cost ICP-MS. In addition, we performed theoretical calculations of the selective CER using density functional theory (DFT). Therefore, this label-free and simple separation AS/ICP-MS sensing platform shows great potential for biomarker analysis.

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.

Determination of cadmium in water samples by fast pyrolysis – Chemical vapor generation atomic fluorescence spectrometry using titanium hydride powder as a hydrogen source

A method for the determination of cadmium by pyrolysis chemical vapor generation (Py-CVG) atomic fluorescence spectrometry using titanium hydride (TiH2) as a reducing agent has been proposed. Under optimal conditions (T = 500 °C, TiH2 = 20 mg, argon = 350 ml min−1), the mass and concentration detection limits were 0.21 ng and 0.52 ng ml−1, respectively, and precision(RSD,%)for ten replicated measurements for a 5 ng cadmium was 5.2. The proposed method has not only a good interference tolerance but also a very stable signal plateau in a very wide range of acid concentrations. The method was successfully applied to analyze trace amounts of cadmium in two reference materials for environmental water, and the results were in good agreement with the certified reference values.

Multimode MicroRNA Sensing via Multiple Enzyme-Free Signal Amplification and Cation-Exchange Reaction.

The detection of biomarkers requires not only high sensitivity but also different signal reading methods depending on the actual situation. Herein, the luminescent properties of CdTe quantum dots (QDs) were exploited, where CdTe QDs were used as shared signal molecules. Combining multiple types of nucleic acid and chemical signal amplification techniques, and various signal detection techniques, a magnetic nanoparticle (NP) and filter-assisted separation multimode sensing strategy has been developed. In this work, miRNA-141 was selected as a representative target, which can trigger the catalyzed hairpin assembly and hybrid chain reaction enzyme-free nucleic acid signal amplification that generates long double-stranded DNA. Subsequently, the chemical amplification of silver NPs (Ag NPs) that release a large amount of Ag+ was introduced into the system. Finally, the cation-exchange reaction between CdTe QDs and Ag+ was utilized to quench the fluorescence (FL) of the CdTe QDs, releasing free Cd2+. The visual/FL/chemical vapor generation-atomic fluorescence spectrometry (CVG-AFS)/inductively coupled plasma mass spectrometry (ICP-MS) method could then be performed for the analysis of miRNA. After investigating its experimental performance, it has been found that 10 fM can be differentiated from the blank solution with the naked eye. In addition, FL/CVG-AFS/ICP-MS methods all displayed good analytical capability for target detection, and the limits of detection (LODs) are as low as fM, which show high target sequence selectivity. This platform was applied to investigate miRNA-141 expression in various cancer cells, which can accurately detect in the range of 100-100 000 MDA-MB-231 cells (breast cancer cell lines), with an LOD of 15 cells. Therefore, the multimode sensing strategy based on a single signal molecule and multiple signal amplification strategies is an applicable and versatile detection method of biomarkers; it can even achieve point-of-care testing, improving the accuracy and efficiency of medical diagnosis.

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.

Investigation of organic phase chemical vapor generation-atomic fluorescence spectrometry in the determination of tin

ABSTRACT In this work, the application of organic phase chemical vapour generation (CVG)-atomic fluorescence spectrometry (AFS) was extended, firstly investigating the feasibility and analytical performance for the determination of tin. It was found that the hydride of tin could be generated in octanol media, and then successfully detected by AFS. Compared to the traditional hydride generation (HG)-AFS, the analytical performance of the developed organic phase system for the determination of tin was improved. Under the optimal conditions, the limit of detection (LOD) was 0.1 µg L−1.

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.

Determination of total inorganic arsenic in water samples by cadmium ion assisted photochemical vapor generation-atomic fluorescence spectrometry

A novel approach based on cadmium ions assisted photochemical vapor generation (PVG) combined with atomic fluorescence spectrometry (AFS) was proposed for sensitive and accurate detection of total inorganic arsenic. In this work, the prereduction step of As(V) to As(III) was avoided. An approximate 10-fold improvement in sensitivity was achieved for both As(III) and As(V) with the existence of 20 mg L−1 Cd2+ in the 30% (v/v) acetic acid solution for 60 s UV irradiation. Under the optimal experimental conditions, detection limits of 0.05 μg L−1 were obtained for As(III) and As(V). The relative standard deviations (RSD) of the 20 μg L−1 As(III)/As(V) standard solution from 11 times measurements were both within 2%. The accuracy of the proposed approach was verified by analyzing of several surface water samples using standard addition method, Yangtze river waters and Funan river waters, with recoveries from 94% to 105%, which were in good agreement with the results from ICPMS determination.

Integration of Flow Injection Capillary Liquid Electrode Discharge Optical Emission Spectrometry and Microplasma-Induced Vapor Generation: A System for Detection of Ultratrace Hg and Cd in a Single Drop of Human Whole Blood.

A simple and miniature analytical system was developed to determine Hg and Cd in small amounts of samples by integrating flow injection capillary liquid electrode discharge (CLED) optical emission spectrometry (OES) and microplasma-induced vapor generation (PIVG) atomic fluorescence spectrometry (AFS). With the assistance of the inherent capillary driving force and the force arising from the solution vaporization in the microplasma, the sample solution was automatically transported into the discharge chamber wherein analytes were simultaneously excited to generate their atomic emission lines and converted to their volatile species. Subsequently, the volatile species were further swept into AFS for their further determination. Therefore, the same sample could be successively analyzed by OES and AFS. Owing to the unique independent linear-range and sensitivity of CLED-OES and PIVG-AFS, the developed system not only significantly extended its linear range to 6 orders of magnitude but also remarkably reduced the sample consumption to several microliters. Thus, wide linear-range and ultrasensitive determination of Hg and Cd in limited amounts of samples were accomplished simply by sharing one single capillary liquid electrode discharge source. Under the optimized conditions, limits of detection (LODs) of 10 μg L-1 were obtained for both Hg and Cd when CLED-OES was used as a detector, whereas the LODs for Hg and Cd were improved to 0.03 μg L-1 and 0.04 μg L-1 with AFS detector, respectively. In addition, the extremely wide linear-range of 0.001-100 mg L-1 and 0.001-40 mg L-1 were obtained for Hg and Cd, respectively. The potential application of this method was validated by successfully analyzing three Certified Reference Materials (ZK021-1, GBW(E)090033, and GBW(E)090034) and six human blood samples.

Determination of cadmium in seawater by chelate vapor generation atomic fluorescence spectrometry

A method for the determination of cadmium in seawater by chelate vapor generation (Che-VG) atomic fluorescence spectrometry is described. Several commercially available chelating agents, including ammonium pyrrolidine dithiocarbamate (APDC), sodium dimethyl dithiocarbamate (DMDTC), ammonium dibutyl dithiophosphate (DBDTP) and sodium O,O-diethyl dithiophosphate (DEDTP), are compared with sodium diethyldithiocarbamate (DDTC) for the Che-VG of cadmium, and results showed that DDTC and DEDTP had very good cadmium signal intensity. The effect of the conditions of Che-VG with DDTC on the intensity of cadmium signal was investigated. Under the optimal conditions, 85±3% Che-VG efficiency is obtained for cadmium. The detection limit (3σ) obtained in the optimal conditions was 0.19ngml−1. The relative standard deviation (RSD, %) for ten replicate determinations at 2ngml−1 Cd was 3.42%. The proposed method was successfully applied to the ultratrace determination of cadmium in seawater samples by the standard addition method.

Selective reduction-based, highly sensitive and homogeneous detection of iodide and melamine using chemical vapour generation-atomic fluorescence spectrometry

A selective reduction-based method was proposed for the sensitive detection of iodide and melamine using chemical vapour generation (CVG) coupled with atomic fluorescence spectrometry (AFS), meanwhile expanding the application of CVG-AFS.

Determination of cadmium in water samples by fast pyrolysis–chemical vapor generation atomic fluorescence spectrometry

A pyrolysis-vapor generation procedure to determine cadmium by atomic fluorescence spectrometry has been established. Under fast pyrolysis, cadmium ion can be reduced to volatile cadmium species by sodium formate. The presence of thiourea enhanced the efficiency of cadmium vapor generation and eliminated the interference of copper. The possible mechanism of vapor generation of cadmium was discussed. The optimization of the parameters for pyrolysis–chemical vapor generation, including pyrolysis temperature, amount of sodium formate, concentration of hydrochloric acid, and carrier argon flow rate were carried out. Under the optimized conditions, the absolute and concentration detection limits were 0.38ng and 2.2ngml−1, respectively, assuming that 0.17ml of sample was injected. The generation efficiency of was 28–37%. The method was successfully applied to determine trace amounts of cadmium in two certified reference materials of Environmental Water (GSB07-1185-2000 and GSBZ 50009-88). The results were in good agreement with the certified reference values.