Hydride Generation Research Articles

Development of a miniaturized hydride generation-dielectric barrier discharge atomic absorption spectrometer

A miniaturized atomic absorption spectrometer (AAS) was proposed with a planar dielectric barrier discharge (DBD) microplasma as an atomizer, a charge coupled device (CCD) spectrometer as a spectral detector, and a hydride generation (HG) unit as a sampler, and the potential analytical capability was evaluated through the determination of cadmium. Auxiliary hydrogen was added to enhance the atomic absorption signals and the potential mechanism of enhancement effect was studied by use of various techniques. The HG-DBD-AAS was further applied to the determination of Cd, yielding a 1.7-fold enhancement in AAS response with added hydrogen and a limit of detection (LOD) of 0.3 μg L−1 under optimized conditions. Good agreement with the certified values, and desirable spike recoveries ranging between 98% and 108%, were obtained for two certified reference materials and several real water samples, respectively. It can be useful in field analysis of many trace elements with high detectability.

Selenium speciation in soils using flow injection hydride generation atomic absorption spectrometry with on-line removal of organic matter interferences

A method based on flow injection hydride generation atomic absorption spectrometry (FI-HGAAS) with an on-line pre-reduction of Se(VI) to Se(IV) was developed and optimized to determine phosphate-extractable Se (0.1 M phosphate buffer KH2PO4/K2HPO4 at pH 7). The extracted fraction involves water-soluble Se (i.e. the most mobile Se fraction) and exchangeable Se (i.e. sorbed onto soil component surface). Kinetic discrimination mechanisms allowed the complete removal of interferences caused by organic matter due to the formation of humic substances (HS)–Se(IV) complexes observed when batch pre-reduction processes were used. Se(IV) and Se(VI) recoveries ranged 95–105% at a fortification level of 150 μg kg−1. The pre-reduction was efficiently carried out in 20 s in a 6 M HCl medium at 100 °C. Results from phosphate-extractable fractions were comparable to those obtained by ICP-MS. Se bound to organic matter was released digesting the remaining material from the phosphate buffer extraction with 0.1 M K2S2O8. Detection and quantification limits were 15 μg kg−1 Se and 50 μg kg−1 Se, respectively, in each fraction. The methodology was applied to 10 agricultural soils from Argentina with total Se concentration levels between 130 μg kg−1 and 419 μg kg−1.

Hydride Generation on the Cu-Doped CeO2(111) Surface and Its Role in CO2 Hydrogenation Reactions

Ceria-based catalysts exhibit great activity in catalyzing selective hydrogenation of CO2 to methanol. However, the underlying mechanism of this reaction, especially the generation of active H species, remains unclear. In this work, we performed extensive density functional theory calculations corrected by on-site Coulomb interaction (DFT + U) to investigate the H2 dissociation and the reaction between the active H species and CO2 on the pristine and Cu-doped CeO2(111) (denoted as Cu/CeO2(111)) surfaces. Our calculations evidenced that the heterolytic H2 dissociation for hydride generation can more readily occur on the Cu/CeO2(111) surface than on the pristine CeO2(111) surface. We also found that the Cu dopant can facilitate the formation of surface oxygen vacancies, further promoting the generation of hydride species. Moreover, the adsorption of CO2 and the hydrogenation of CO2 to HCOO* can be greatly promoted on the Cu/CeO2(111) surface with hydride species, which can lead to the high activity and selectivity toward CO2 hydrogenation to methanol.

Chemometric classification and discrimination of herbal dietary supplements based on ICP-MS elemental profiling

This study presents the determination of elemental profiling of representative dietary herbal supplements which were purchased on the Croatian market in the forms of capsules, powders, jams or liquids. Using inductively coupled plasma mass spectrometry (ICP-MS), twenty-four elements in eighty-seven different samples were determined. Electrothermal atomic absorption with hydride generation technique (HG-ETAAS) applied for the selenium determination in all samples gave the similar results as ICP-MS technique. Elemental profiling resulted with determination of major constituents Na, Mg, Ka and Ca with mean concentration values of 2900, 2700, 9200, and 16,600 mg kg−1, respectively. Elements of middle concentration range were: B, Al, Mn, Fe, Zn and Sr (31.8–1050 mg kg−1). Trace and ultra-trace levels comprise of Se, V, Cr, Co, Ni, Cu, As, Mo, Cd, Sb, Hg, Tl and Pb (21.7–11,300 µg kg−1). Using PLS-DA statistical analysis, the elements Se, Na, Fe, Co, Tl, and Zn, were established as the marker elements with the greatest discriminating power between supplement samples. Multivariate PCA analysis resulted with the successful discrimination of Se and Zn enriched supplements. Hierarchical cluster analysis (HCA) enhanced the recognition of similarities in sub-clusters of samples. Minor discrepancies in trace and ultra-trace elemental profiles revealed Hg, As, Cd, Pb, Cr and Co as the key elements for discrimination between two groups of Ayurvedic and spirulina-based supplements. The HCA method also allowed visualization of the exceptional elemental profile of several mixed-herb supplements. There were distinctive features of herbal dietary supplements with peculiar influences of botanical, environmental and/or production conditions on their elemental profile.

Electrocatalytic metal hydride generation using CPET mediators.

Transition metal hydrides (M-H) are ubiquitous intermediates in a wide range of enzymatic processes and catalytic reactions, playing a central role in H+/H2 interconversion1, the reduction of CO2 to formic acid (HCOOH)2 and in hydrogenation reactions. The facile formation of M-H is a critical challenge to address to further improve the energy efficiency of these reactions. Specifically, the easy electrochemical generation of M-H using mild proton sources is key to enable high selectivity versus competitive CO and H2 formation in the CO2 electroreduction to HCOOH, the highest value-added CO2 reduction product3. Here we introduce a strategy for electrocatalytic M-H generation using concerted proton-electron transfer (CPET) mediators. As a proof of principle, the combination of a series of CPET mediators with the CO2 electroreduction catalyst [MnI(bpy)(CO)3Br] (bpy = 2,2'-bipyridine) was investigated, probing the reversal of the product selectivity from CO to HCOOH to evaluate the efficiency of the manganese hydride (Mn-H) generation step. We demonstrate the formation of the Mn-H species by in situ spectroscopic techniques and determine the thermodynamic boundary conditions for this mechanism to occur. A synthetic iron-sulfur cluster is identified as the best CPET mediator for the system, enabling the preparation of a benchmark catalytic system for HCOOH generation.

Potentially toxic elements contamination, risk assessment via consumption, and spatial distribution of pollution and evaluation indices in the alpine lakes, Pakistan

ABSTRACT The current study investigated potentially toxic elements (PTE) contaminations in the water of alpine lakes of Gilgit-Baltistan, Northern Pakistan. Water samples (n = 46) of various alpine lakes were collected and analysed for PTE determination through atomic absorption spectroscopy (AAanalyst 700, PerkinElmer, USA). Arsenic (As) in water was measured using a mercury hydride generation system. PTE concentrations in water of alpine lakes were observed below the upper limit of the world health organisation (WHO) drinking water guidelines, except for iron (Fe, 14%), chromium (Cr, 10%), and As (2%) of samples. The highest mean concentrations of Fe (233 ± 22.4 µg/L) and Cr (36.3 ± 4.20 µg/L) were noted in the water of Rama Lake and the As (6.20 ± 0.65 µg/L) in the Lower Kachura Lake. PTE concentrations in the water of alpine lakes was evaluated for the elements pollution index (EPI), elements evaluation index (EEI), and risk indices. The values of EPI and EEI for PTE in the water of alpine lakes were found far below the threshold limits. Higher mean chronic daily intake (CDI) values were observed for Fe and zinc (6.67 ± 1.09 and 4.95 ± 2.65 µg/kg-day) in the Rama and Upper Kachura Lakes, respectively. Determined hazard quotient (HQ) values for PTE were noted as> 1. However, the HQ value for As was (1.4 ± 0.06) which may have a detrimental effect on the health of children. Cancer risk of As and HQ values for other elements were found within the allowable limits of consumption in drinking water. Statistical analysis revealed that geogenic sources are the main PTE contaminations contributors in the water of alpine lakes.

Ultrasensitive Determination of Arsenic in Juvenile Eyeshadow by Novel Dispersive Magnetic Solid-Phase Extraction (MSPE) and Flow Injection Analysis – Hydride Generation Atomic Absorption Spectrometry (FIA-HG-AAS)

A new procedure is reported for arsenic preconcentration in juvenile eyeshadow using maghemite nanoparticles (γ-Fe2O3) and determination by flow injection analysis – hydride generation atomic absorption spectrometry (FIA-HG-AAS). Maghemite nanoparticles were synthesized and characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and N2 adsorption measurements at −196 °C. The results showed a crystalline size of 9.1 nm and a surface area of 106 m2 g−1. The experimental conditions for the hydride generation system and the preconcentration process were optimized using a central composite design. For hydride generation, the levels of the concentration of the factors HCl, NaBH4, and flow of carrier gas were optimized, with optimal conditions of 4 mol L−1, 1.1% (m/v), and 145 mL min−1, respectively. The optimized conditions obtained for the adsorption process were a pH equal to 5.3, a mass of γ-Fe2O3 of 184 mg, and stirring time of 41 min in the presence of the sample matrix. The enrichment factor was 50, and the limit of detection was 0.9 μg g−1. Recovery values ranged from 75 to 99%.

Speciation of inorganic arsenic in aqueous samples using a novel hydride generation microfluidic paper-based analytical device (µPAD)

The development of the first microfluidic paper-based analytical device (µPAD) for the speciation of inorganic arsenic in environmental aqueous samples as arsenite (As(III)) and arsenate (As(V)) which implements hydride generation on a paper platform is described. The newly developed µPAD has a 3D configuration and uses Au(III) chloride as the detection reagent. Sodium borohydride is used to generate arsine in the device’s sample zone by reducing As(III) in the presence of hydrochloric acid or both As(III) and As(V) (total inorganic As) in the presence of sulfuric acid. Arsine then diffuses across a hydrophobic porous polytetrafluoroethylene membrane into the device’s detection zone where it reduces Au(III) to Au nanoparticles. This results in a color change which can be related to the concentration of As(III) or total inorganic As (i.e., As(III) and As(V)) concentration. Under optimal conditions, the µPAD is characterized by a limit of detection of 0.43 mg L−1 for total inorganic As (As(III) + As(V)) and 0.41 mg L−1 for As(III) and a linear calibration range in both cases of 1.2–8.0 mg As L−1. The newly developed µPAD-based method was validated by applying it to groundwater and freshwater samples and comparing the results with those obtained by conventional atomic spectrometric techniques.Graphical abstract

Investigation of selenium nutritional status and dietary pattern among children in Kashin-Beck disease endemic areas in Shaanxi Province, China using duplicate portion sampling method.

Selenium deficiency is a primary risk factor of Kashin-Beck disease (KBD). This study aimed to investigate whether children in endemic areas could maintain sufficient selenium intake after termination of selenium supplement administration, and evaluate their comprehensive nutritional status and dietary structure. Duplicate portion sampling combined with a questionnaire was adopted to collect data on categories and quantity of all food ingested in three consecutive days. Occipital hair was also collected to detect selenium content by hydride generation atomic fluorescence spectrometry (HGAFS). CDGSS3.0 software and factor analysis were integrated to assess the children's comprehensive nutritional status and dietary structure. This study included 240 sex-matched (1:1) children aged 7-12years from KBD endemic (n=120) and non-endemic (n=120) areas. Overall, 720 solid food, 720 liquid, and 240 hair samples were collected for selenium determination. The mean selenium level in hair of children in endemic areas (0.38±0.16mg/kg) was significantly lower than that in children in non-endemic areas (0.56±0.28mg/kg, Z=-5.249, p<0.001). The dietary selenium intake of children in endemic areas was 40.0% lower than that in children in non-endemic areas (Z=-9.374, p<0.001). Children in endemic areas consumed significantly less diverse dietary items leading to significantly less intake of multiple nutrients compared to children in non-endemic areas. The dietary selenium intake of most children in endemic areas was less than the recommended amount. The dietary structure of children was undiversified, which limited the intake of multiple nutrients. Therefore, comprehensive nutrition rather than sole selenium intake should be the primary concern in the future.

Germanium in Lake Geneva (Switzerland/France) along the spring productivity period

In this study we present, for the first time, profiles of germanium and its species (inorganic, monomethyl and dimethyl germanium) in a lake: Lake Geneva (Switzerland/France). The period studied covers the spring productivity phase, from January to June 2021, through monthly sampling campaigns in a location where the lake is about 70 m deep (Petit Lac). They have been complemented with samplings in April and June in the lake's deepest point (Grand Lac) and in the main river tributaries. The concentrations of the different species have been measured by a hydride generation – cryotrapping – inductively coupled plasma mass spectrometry (HG-CT-ICP MS/MS) method. Particular attention has been paid to the reliability of the analytical data. When the lake was well mixed, inorganic germanium concentrations were 1.4 ng L−1. Concentration profiles evolved over the season, progressively displaying a typical nutrient-type behaviour, which exactly followed those of silica. Methyl germanium showed conservative behaviour over the entire season with an average concentration of about 0.1 ng L−1. Dimethyl germanium could be detected in some cases but not quantified. Our observations confirm previous studies in oceans but with the difference that, contrary to oceans, inorganic germanium concentrations in the lake largely exceed the concentration of organic species.

Arsenic Trioxide Therapy During Pregnancy: ATO and Its Metabolites in Maternal Blood and Amniotic Fluid of Acute Promyelocytic Leukemia Patients.

Acute promyelocytic leukemia (APL) is extremely fatal if treatment is delayed. Management of APL in pregnancy is a challenging situation. Arsenic trioxide (ATO) is successfully applied to treat APL. ATO can be transformed into different arsenic species [arsenite (AsIII), monomethylated arsenic (MMA, consists of MMAIII and MMAV), dimethylated arsenic (DMA, consists of DMAIII and DMAV), and arsenate (AsV)], which produce different toxic effects. Investigating the maternal and fetal exposure to arsenic species is critical in terms of assessing maternal and fetal outcomes, choice of optimal treatment, and making decisions for attempting to preserve the obstetrical and fetal wellbeing. In this study, maternal blood and amniotic fluid (AF) from APL patients treated with ATO in pregnancy and blood samples of non-pregnant patients were collected. Concentrations of inorganic arsenic (iAs, iAs = AsIII+AsV), MMA, and DMA were analyzed by high-performance liquid chromatography–hydride generation–atomic fluorescence spectrometry (HPLC–HG–AFS). The difference in arsenic species of plasma between pregnant patients and non-pregnant patients, distribution of arsenic compounds in AF and maternal plasma, and arsenic penetration into AF were explored. The outcomes of pregnant women treated with ATO and their fetus were analyzed. No significant differences in arsenic concentration, percentage, and methylation index [PMI: primary methylation index (MMA/iAs); SMI: secondary methylation index (DMA/MMA)] between pregnant women and non-pregnant women (p > 0.05) were observed. The mean ratios of AF to maternal plasma were as follows: iAs, 2.09; DMA, 1.04; MMA, 0.49; and tAs, 0.98. Abortion rate is higher with the diagnosis at an earlier gestational age, with 0%, 67%, and 100% of pregnancies ending in abortion during the third, second, and first trimester, respectively. The age of the pregnant women, the dose of ATO, and the duration of fetal exposure in utero had no influence on fetal outcomes. All APL women achieved complete remission (CR). Collectively, ATO and its metabolites can easily cross the placenta. Levels and distribution of arsenic species in maternal plasma and AF gave evidence that arsenic species had a different ability to penetrate the placenta into AF (iAs > DMA > MMA) and indicated a relatively high fetal exposure to ATO and its metabolites in utero. Gestational age at diagnosis was more likely to be closely related to fetal outcomes, but had no effects on mother outcomes.

Determination and speciation of selenium in water samples collected from Muğla (Turkey) province by hydride generation atomic absorption spectrometry

In this work, determination of selenium in various water samples was done by using hydride generation atomic absorption spectrometry. The most appropriate values of HCl concentration, NaBH4 concentration, NaOH concentration, flow rate of argon and flow rate of waste solution were determined. The optimum concentration of the HCl, NaBH4 and NaOH solutions were found to be 7.0 mol L−1, 1.0% and 0.75%, respectively. The optimum flow rate of Ar gas and waste solution were also found to be 100.9 mL min−1 and 4.0 mL min−1, respectively. Values of LOD and LOQ were calculated separately for total Se and Se(IV). LOD and LOQ values were calculated 0.56 μg L−1, 1.87 μg L−1 for total Se and 0.72 μg L−1, 2.40 μg L−1 for Se(IV), respectively. The precision was evaluated by relative standard deviation (RSD%) was found to be 3.5% for total Se and 3.1% for Se(IV) (n = 11). A standard reference material (NIST 1643e) was used in order to check the accuracy of the proposed method. There was a good agreement between certified and found values for standard reference material. The method was applied to the analysis of total Se and Se(IV) concentrations in tap water samples collected from the various regions of Muğla. Proposed method showed spike recovery ranges from 92% to 116% in water samples.

Mo3+ hydride as the common origin of H2 evolution and selective NADH regeneration in molybdenum sulfide electrocatalysts

Hydride transfers are key to a number of economically and environmentally important reactions, including H2 evolution and NADH regeneration. The electrochemical generation of hydrides can therefore drive the electrification of chemical reactions to improve their sustainability for a green economy. Catalysts containing molybdenum have recently been recognized as among the most promising non-precious catalysts for H2 evolution, but the mechanism by which molybdenum confers this activity remains debated. Here we show the presence of trapped Mo3+ hydride in amorphous molybdenum sulfide (a-MoSx) during the hydrogen evolution reaction and extend its catalytic role to the selective hydrogenation of the biologically important energy carrier NAD to its active 1,4-NADH form. Furthermore, this reactivity applies to other HER-active molybdenum sulfides. Our results demonstrate a direct role for molybdenum in heterogeneous H2 evolution. This mechanistic finding also reveals that molybdenum sulfides have potential as economic electrocatalysts for NADH regeneration in biocatalysis.

A Triple Photoredox/Cobalt/Brønsted Acid Catalysis Enabling Markovnikov Hydroalkoxylation of Unactivated Alkenes.

We demonstrate Markovnikov hydroalkoxylation of unactivated alkenes using alcohols through a triple catalysis consisting of photoredox, cobalt, and Brønsted acid catalysts under visible light irradiation. The triple catalysis realizes three key elementary steps in a single catalytic cycle: (1) Co(III) hydride generation by photochemical reduction of Co(II) followed by protonation, (2) metal hydride hydrogen atom transfer (MHAT) of alkenes by Co(III) hydride, and (3) oxidation of the alkyl Co(III) complex to alkyl Co(IV). The precise control of protons and electrons by the three catalysts allows the elimination of strong acids and external reductants/oxidants that are required in the conventional methods.

Simple and Fast Two-Step Fully Automated Methodology for the Online Speciation of Inorganic Antimony Coupled to ICP-MS

A very simple, fast and non-chromatographic methodology for inorganic antimony speciation based on Multisyringe Flow Injection Analysis (MSFIA) employing online hydride generation (HG) ICP-MS was developed. The fully automated analysis is performed in two steps: firstly, Sb(III) is quantified by ICP-MS after chemical vapor generation; then, total antimony is determined in the presence of potassium iodide as a pre-reducer of Sb(V) to Sb(III). The Sb(V) concentration is quantified by the difference between the total antimony and Sb(III) concentrations, reaching an analysis frequency of 30 h−1. The optimization was performed using a Box Behnken design. The MSFIA-HG-ICP-MS system allows the antimony speciation analysis with a detection limit of 0.016 µg L−1 for Sb(III), working in a linear range of 0.053 to 5.0 µg L−1. This method was applied for the determination of Sb(III) and Sb(V) in water samples from Maiorca Island, Spain, and the concentrations found varied from 0.10 to 0.14 µg L−1 for Sb(III) and from 0.12 to 0.28 µg L−1 for Sb(V). The results were validated by addition/recovery tests, obtaining recoveries between 90 and 111% in both cases. Furthermore, a good precision was achieved, 1.4% RSD, and sample and reagent consumption were reduced to a few mL, with the consequent decrease in waste generation. Thus, the proposed method is a good tool for the speciation of inorganic antimony at ultra-trace levels in waters, allowing its risk assessment.

The Status of Selenium and Zinc in the Urine of Children From Endemic Areas of Kashin-Beck Disease Over Three Consecutive Years.

Selenium deficiency is one of the main risk factors for Kashin-Beck disease (KBD). This study aimed to detect the status of selenium and zinc in the urine of children from endemic areas of KBD over three consecutive years and to evaluate whether selenium and zinc levels in children in Shaanxi Province remain normal after stopping selenium supplementation. The samples of urine were collected in consecutive years (2017–2019) to detect selenium content by hydride generation atomic fluorescence spectrometry (HGAFS) and to detect zinc content by atomic absorption spectrophotometry (AAS). Generalized estimation equation (GEE) analysis was integrated to assess the comprehensive nutritional status and dietary structure of children. Data were processed in duplicate and analyzed by SPSS 18.0. This study included 30 X-ray-positive KBD cases and 123 healthy children aged 7–12 years. A total of 424 urine and 137 hair samples were collected over three consecutive years for selenium determination. The mean value of urinary selenium in all subjects was 6.86 μg/l (2017), 8.26 μg/l (2018), and 4.04 μg/l (2019), and the mean value of urinary zinc in all subjects was 0.36 mg/l (2017), 0.39 mg/l (2018), and 0.31 mg/l (2019) for the three consecutive years of 2017–2019. The mean values of urinary selenium were 6.56 and 6.94 μg/l (2017), 8.69 and 8.14 μg/l (2018), and 4.57 and 3.90 μg/l (2019) in the KBD-X and normal groups, respectively; and the mean value of urinary zinc were 0.38 and 0.35 mg/l (2017), 0.41 and 0.39 mg/l (2018), and 0.43 and 0.28 mg/l (2019) in the KBD-X and normal groups, respectively. The mean value of hair selenium in 137 subjects was 275.08 μg/kg and the mean values of hair selenium were 267.48 and 276.61 μg/kg in the KBD-X group and normal group, respectively. The level of selenium/zinc showed a trend of increasing first and then decreasing during the three consecutive years. The level of selenium in all subjects from the endemic areas was lower than normal, which reminds us to monitor the state of KBD constantly and adjust selenium salt supplementation in accordance with the changes in the KBD state.

Arsenic-contaminated drinking water and associated health risks in children from communities located in a geothermal site of Michoacán, México: Monte Carlo probabilistic method

Arsenic occurs naturally in ground and spring waters in several geothermal regions in México as a result of natural geochemical processes. Therefore, the goal of this study is to assess the probabilistic health risk in children exposed to arsenic by drinking water from communities located in the geothermal site of Zinapécuaro, Michoacán, México. The water sampling was done monthly for one year and total inorganic arsenic was determined using Hydride Generation coupled with Atomic Absorption Spectrometry. The health risk was assessed using the Monte Carlo probabilistic method. The arsenic levels in water were found to be in the range of 10.4 to 58.9 μg/L, with the highest levels from the hot springs. For children, the 95th percentile of Hazard Index was (HI) >1 for all study sites, with the highest mean (HI = 11 ± 2.9) for Taimeo’s spring water. The ingestion pathway predominantly contributed > 95% to the total health risk in comparison to the dermal exposure route. These results show the potential non-cancerous effects of arsenic in drinking water for children are high. For children and adults, the 95th percentile of Total Cancer Risk (TCR) was 4.7 × 10−4 and 1.2 × 10−3 respectively, exceeding the US EPA safe threshold of 1 × 10−4, which is an unacceptable cancer risk. Sensitivity analysis indicated that arsenic concentration in drinking water, body weight and arsenic intake for children were the most relevant variables on the output parameter HI. Consequently, the environment and health authorities must make greater efforts to provide safe drinking water to protect the residents of Zinapécuaro County.

Direct solid sampling of biological species for the rapid determination of selenium by high-resolution continuum source graphite furnace atomic absorption spectrometry

A direct solid sampling method based on high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) for the determination of selenium (Se) in biological tissues was optimized. The main analytical line of Se at 196.0267 nm was used to carry out all HR-CS AAS measurements. Different chemical modifiers were evaluated to prevent the loss of Se during the application of the GFAAS temperature program and avoid the interferences due to the presence of phosphorus compounds in sample matrix. The best results were achieved using ruthenium coated platforms and a palladium nanoparticle suspension (Pd NP) as co-injected modifier. Calibration was performed using aqueous standard solutions of Se(IV). For solid sampling, the optimal range of sample mass was between 0.2 and 0.8 mg. The limit of detection (LOD) was 0.06 ng (0.075 μg g−1 using a sample mass of 0.8 mg). The developed solid sampling HR-CS GFAAS method was used for Se determination in two certified reference materials of dogfish tissues and lyophilized and powdered real samples of fish tissues and chicken liver. The precision obtained in these analyses, expressed as relative standard deviation (RSD), was between 5.5 and 8.6% (n = 6). For validation purposes, the results obtained by the solid sampling HR-CS GFAAS method were compared with those found performing the analysis by HR-CS hydride generation AAS (HR-CS HGAAS) after microwave acid digestion of the samples. The Se concentrations obtained for both methods agreed at a 95% confidence level (Student's t-test), indicating the suitability of the proposed solid sampling HR-CS GFAAS method to determine Se in biological samples.

Electrothermal Desolvation-Enhanced Dielectric Barrier Discharge Plasma-Induced Vapor Generation for Sensitive Determination of Antimony by Atomic Fluorescence Spectrometry.

A novel simple electrothermal desolvation-enhanced dielectric barrier discharge plasma-induced vapor generation (ETD-DBD-PIVG) method has been developed for sensitive Sb determination by atomic fluorescence spectrometry (AFS). In our proposed ETD-DBD-PIVG, 20 μL sample solution was dried first; then, the resulting solution residue was directly converted into molecular volatile species efficiently through the interactions with hydrogen-doped DBD plasma; and finally, it was transported to AFS for detection. It was found that the desolvation process could greatly enhance Sb vapor generation, and the Sb fluorescence signal intensity is almost independent of its speciation, where comparable sensitivity is achieved for Sb(III) and Sb(V), enabling efficient total Sb detection without pre-reduction. Influencing parameters were evaluated in detail, including heating time, discharge gap, solution pH, and flow rates of argon and hydrogen, as well as coexisting ion interference. Under optimized conditions, the limit of detection was calculated as 0.86 μg L-1 (17.2 pg) for Sb. The accuracy of the proposed method was validated by the analysis of certified reference materials of simulated natural water samples and several river water samples. Compared with conventional hydride generation, the new ETD-DBD-PIVG offers an alternative green vapor generation technique with several advantages: (1) it eliminates the use of a sample flow system (e.g., no use of any syringe or peristaltic pump); instead, 20 μL of a sample is directly pipetted onto the glass plate for analysis; (2) it greatly simplifies the sample pretreatment steps as no pre-reduction process is needed; (3) it is sensitive and suitable for volume-limited sample analysis: efficient Sb vapor generation without chemical reducing reagents in ETD-DBD-PIVG enables Sb detection with an absolute limit at the picogram level. All the results demonstrate that the proposed method provides a simple, green, and sensitive method for Sb determination and it can also be extended to other elements such as Cd and As.

Analytical Methods for the Quantification of Selenium Species in Biological Matrix: Where are We?

Objective: Over the years, scientific investigations have proven the importance of selenium as an essential element for mammals, emphasizing its activity against many diseases and even its prophylactic effects. It is also established now that a malconsumption of selenium can be harmful. Therefore, the nature and the concentration of selenium and its derivatives found in the diet, the body, and even in the environment, for example, in the soil, should be determined carefully. Methods: In this review, analytical methods for speciation and determination of selenium concentrations in biological samples are summarized. Results: Methods ranging from routine to cutting-edge are explored, focusing on their analytical characteristics, such as specificity for discrete selenium species, sensitivity, accuracy, reproducibility, and skills required. Conclusion: There are already numerous studies regarding the analysis of selenium species. Beyond the method employed for actual measurements, we propose to review the preanalytic steps for sample handling in biological matrices, which directly affect results that will be more accurate with careful pretreatment. Furthermore, to reach better outcomes in terms of the identification of selenium species, different combinations of techniques might be the answer. We highlight here the last and the cutting-edge methods to identify and quantify selenium such as, high-performance liquid chromatography combined to inductively coupled plasma mass spectrometry (HPLC-ICP-MS), hydride generation atomic absorption spectrometry (HG-AAS), hydride-generation combined to atomic fluorescence spectrometry (HG-AFS), or to inductively coupled plasma optical emission spectrometry (HG-ICP-OES). This review emphasizes the importance of such investigations and the need to achieve reliable, safe, and effective quantification and methods of determination.