On line automated system for the determination of Sb(V), Sb(III), thrimethyl antimony(v) and total antimony in soil employing multisyringe flow injection analysis coupled to HG-AFS

On-site monitoring of dissolved Sb species in natural waters by an automatic system using flow injection coupled with hydride generation atomic fluorescence spectrometer

Antimony (Sb) is a toxic and potentially carcinogenic element in the environment. The toxicity of Sb(III) is ten times that of Sb(V). Therefore, on-site monitoring technique for dissolved Sb species is crucial for the study of Sb environmental processes. In this study, an automated, portable, and cost-effective system was developed for field simultaneous analysis of Sb(III) and Sb(III + V) in natural waters. The system comprised a portable atomic fluorescence spectrometer equipped with a built-in electrochemical H2 generator to reduce the consumption of acid/borohydride solution and make the atomizer more stable for on-site analysis. Flow injection technique was also used to achieve on-line pretreatment of water samples, including filtration, acidification, pre-reduction, and hydride generation procedures. Under the optimal conditions, the limits of detection (3σ, n = 11) of the developed method were 0.015 μg/L and the linear ranges were 0.05-5.0 μg/L for both Sb(III) and Sb(III + V). The relative standard deviations (n = 11) of the spiked samples of Sb(V) were 3.2% (0.05 μg/L), 3.3% (0.2 μg/L), and 1.7% (0.5 μg/L), respectively. The spiked recoveries of lake water, treated wastewater, and seawater ranged from 97.0% to 108.5%. The novel system of flow injection coupled with hydride generation atomic fluorescence spectrometer (FI-HG-AFS) was applied to carry out an 18-h fixed-point monitoring at a secondary settling tank of a wastewater treatment facility in Xiamen University, and a 6-h real-time underway analysis in the surface seawater of Dongshan Bay, China, proving that the system was capable of long-term monitoring in the field.

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.

Selenium inorganic speciation in beers using MSFIA-HG-AFS system after multivariate optimization

In this work, the use of a multisyringe flow injection analysis coupled to hydride generation atomic fluorescence spectrometry (MSFIA-HG-AFS) for inorganic selenium chemical speciation was proposed. A Doehlert design was applied to optimize the experimental conditions for hydride generation (NaBH₄ and HCl concentrations). The limits of quantification (LoQ) obtained were 0.07 µg L^-1, for total inorganic Se, and 0.08 µg L^-1, for Se(IV). Accuracy and precision of the proposed analytical method were evaluated through analysis of standard reference material and addition and recovery tests. The optimized method was applied to analyses of eight samples of beer, produced in Spain, obtaining concentrations for Se(IV) (<0.08 - 0.46 ± 0.01 µg L^-1), total inorganic Se (0.47 ± 0.01 - 3.04 ± 0.62 µg L^-1) and Se(VI) (0.06 ± 0.01 - 3.00 ± 0.59 µg L^-1). The proposed analytical method was accurate, precise and sensitivity for determination of selenium species in beer samples.

Review of the distribution and detection methods of heavy metals in the environment

Heavy metals can be enriched in living organisms and seriously endanger human health and the ecological environment, which has evolved into a significant global environmental problem. Based on summarizing the spatial distribution of heavy metals in the environment, this review introduces heavy metal detection technologies such as inductively coupled plasma mass spectrometry/atomic emission spectrometry, atomic absorption spectrometry, atomic fluorescence spectrometry, and laser-induced breakdown spectrometry. It summarizes their respective advantages, characteristics, and applicability. Besides, atmospheric pressure discharge plasma as a potential heavy metal detection technology is also introduced and discussed in this review. The current research mainly focuses on improving the analytical performance and optimizing the practical application. Furthermore, this review not only summarizes the advantages of atmospheric pressure discharge plasma in the field of element analysis but also summarizes the principal scientific and technical problems to be solved urgently.

Speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry

In this work, a methodology for chemical speciation analysis of inorganic As and Sb in urban dust using slurry sampling and detection by fast sequential hydride generation atomic absorption spectrometry is proposed. Doehlert design and desirability function were used to find the optimum conditions for hydride generation (1.0 mol L^-1 HCl and 0.9% m v^-1 NaBH₄). The accuracy of the analytical method was evaluated by analysis of reference material fly ash (BCR 176R), addition and recovery tests for inorganic As species, and comparison of independent methods for Sb determination in urban dust samples. The determination of the total concentrations of As and Sb and their inorganic species presented good accuracy, between 80 ± 1 and 101 ± 6%. Precision was expressed as the relative standard deviation and was better than 4.7% (n = 3). The limit-of-quantification values were 0.23 and 1.03 mg kg^-1 for As and Sb, respectively. The methodology was applied to eight samples of dust collected in an urban area of Salvador and Jaguaquara cities, Bahia, Northeast, Brazil, with an aerodynamic size lower than 38 μm. Concentrations of pentavalent inorganic species (iAs⁵⁺ and iSb⁵⁺) in relation to trivalent species (iAs³⁺ and iSb³⁺) were found in urban dust collected in the city of Salvador, which are regarded as more toxic for both elements. The enrichment factor and geoaccumulation index (I_geo) values showed that for some samples, the concentrations of iAs and iSb presented strong enrichment and, and regarding environment, strong to moderately polluted by iAs and iSb, with an indication of anthropogenic contributions. The occurrence of these inorganic constituents in the urban area of Salvador can be related with intense industrial activities and vehicular traffic.

Determination of total and bioavailable As and Sb in children's paints using the MSFIA system coupled to HG-AFS

In this study, the use of hydride generation atomic fluorescence spectrometry (HG-AFS) coupled with the multi-syringe flow injection analysis (MSFIA) has been proposed in the application of the Doehlert design to optimise the determination of As and Sb in gouache and tempera children's paints. The determination of the total and bioavailable As and Sb in paint samples from various brands and colours was also investigated. The limits of quantification (LOQ) obtained for the determination of As and Sb were 14.0 and 8.6 ng g-1, respectively. The accuracy and precision of the method were evaluated through recovery tests (by the analyte addition method) at three levels for both elements, and by the analysis of certified reference materials of clay (CRM 052, Loamy Clay 1) and river water (SLRS-4). Twenty paint samples, manufactured in China, Italy, Spain and Brazil, were analysed. The concentrations of As varied between below LOQ (<14 ng g-1) and 136.0 ± 1.1 ng g-1 (average value of 101.0 ng g-1, n = 10), and Sb between below LOQ (<8.6 ng g-1) and 74.0 ± 5.4 ng g-1 (average value of 21.7 ng g-1, n = 17). The children's paint samples presented As and Sb concentrations that were below the maximum values established by the National Institute of Metrology, Quality and Technology (INMETRO), as well as by the European legislation Directive 2009/48/EC. Based on the obtained results for the total As and Sb concentrations, eight samples were selected to evaluate the migration or bioavailability of As and Sb after solubilisation in HCl solution. The obtained results showed that for the eight analysed samples, the concentration of both elements after solubilisation in HCl solution were below the LOQ (<16.2 ng g-1 for As and <7.1 ng g-1 for Sb). These values correspond to the limits of analytical concentrations of As and Sb established by INMETRO and the Brazilian Association of Technical Standards (ABNT). The determined concentrations of As and Sb guarantee the safety (with regards to these elements) for children when using the analysed paint samples since they do not cause any health risk. The analytical method for the determination of the total and bioavailable As and Sb in children's paints was efficient, accurate and precise.

Simultaneous oxidation and removal of Sb(III) from water by using synthesized CTAB/MnFe2O4/MnO2 composite

Low levels of antimony (Sb) can be effectively removed from water by adsorption onto various materials, and searching for low-cost and high-efficiency new adsorbents has been a hot topic in recent years. In the present study, the performance of cetyltrimethylammonium bromide (CTAB) modified MnFe₂O₄/MnO₂ composites (CTAB/MnFe₂O₄/MnO₂) as an adsorbent for Sb(III) removal from aqueous solution was investigated. Kinetic study revealed that adsorption of Sb(III) by CTAB/MnFe₂O₄/MnO₂ was fast in the first 430 min and the equilibrium was achieved within 1440 min. The adsorption kinetic data were well fitted with pseudo-second-order model. The maximum adsorption capacity of the synthesized adsorbent for Sb(III) at pH 7 calculated from Langmuir adsorption isotherms in batch experiments was 321.03 mg g^-1. During the adsorption process, Sb(III) can be simultaneously oxidized to Sb(V) and the average oxidation percentage reached 95.43% within 1440 min. The adsorption capacity did not significantly vary with pH. Common metal cations (Ca²⁺ and Mg²⁺) slightly enhanced Sb(III) adsorption at pH 7. In comparison, the effect of anions (Cl^-, NO₃^-, and PO₄^3-) on Sb(III) adsorption was not obvious. The results suggest that CTAB/MnFe₂O₄/MnO₂ is a potential cost-effective adsorbent for Sb(III) removal in water treatment.

An efficient protocol to use feedback-controlling digital microfluidic fluorimetric sensor for detection of mercury (II) in coastal seawaters

Mercury ion is a highly toxic anthropogenic pollutants and has serious well-known effects on human. There is an ever-growing demand for convenient detection of mercury driven contaminants in environment, including coastal seawater. However, most of the reported methods are instrument-based and are not easy for portable detection. Our protocol described an efficient Digital Microfluidics method for detecting mercury in coastal seawater samples. It combined the miniaturization/automation potential of digital microfluidics and the sensitivity of fluorescence probe. To overcome a potential risk of driven failure, induced by diversity ion ingredients in seawater, a feedback control loop was included into control system. The method showed satisfied stability and selectivity in Hg sensing under high salinity condition, with the sensitivity of Hg²⁺ at the parts-per-billion level and total testing time of less than 20 s. With the advantages of being fast, amenable to automation and low cost, this protocol is promising for the formation of simple and rapid sensor device, especially for a routine monitoring and emergency detection of Hg/or other metals in coastal waters.

Sequential determination and chemical speciation analysis of inorganic As and Sb in airborne particulate matter collected in outdoor and indoor environments using slurry sampling and detection by HG AAS

In this work, fast sequential determination and chemical speciation analysis of inorganic arsenic and antimony in airborne particulate matter collected in outdoor and indoor environments using slurry sampling and detection by hydride generation atomic absorption spectrometry (HG-AAS) is proposed. A Doehlert design was applied to optimise the hydride generation conditions of As and Sb for fast sequential determination in the same aliquot of particulate matter samples after preparation of the slurry. The limits of quantification (LoQ) obtained for As and Sb were 0.3 and 0.9 ng m^-3, respectively. The accuracy of the analytical method was confirmed by analysis of the certified reference material of urban particulate matter (SRM NIST 1648a), presenting concordance with certified values of 92.7±7.7% for As and 91.2±9.5% for Sb. Precision was expressed as relative standard deviation (% RSD, n=3), with our results presenting values better than 3.4% and 4.2% for total inorganic As and Sb, respectively. For all analysed samples, total As concentrations and its inorganic species were below the LoQ of the analytical method (<0.3 ng m^-3). However, the averages of total inorganic Sb concentrations in airborne particulate matter, collected as total suspended outdoor particles (TSP_outdoor), inhalable particulate matter (PM₁₀), and total suspended indoor particles (TSP_indoor), were 3.1±0.5, 2.4±0.6, and 2.6±0.4 ng m^-3, respectively. Trivalent Sb (Sb³⁺) was the predominant inorganic species in all samples investigated, with mean percentages of 76%, 72%, and 73% in TSP_outdoor, PM₁₀, and TSP_indoor, respectively. The presence of Sb and its predominant inorganic form (Sb³⁺) can be attributed to vehicular traffic close to the sampled urban areas. Therefore, fast sequential determination of As and Sb and their inorganic species in particulate matter samples prepared as slurry by FS-HG-AAS is an efficient, accurate, and precise method and can be successfully applied to routine analysis.

A feedback-controlling digital microfluidic fluorimetric sensor device for simple and rapid detection of mercury (II) in costal seawater

By combination of miniaturization potential of digital microfluidics (DMF) and sensitivity of fluorescence probe, an integrated sensor device has been initially constructed for mercury detection in coastal waters. The actuation feature of the detecting target, seawater droplet, which remains unclear, was basically explored. To overcome a potential risk of driven failure, induced by diversity ion ingredients in seawater, a feedback control loop was included into control system. Analyzing method for coastal waters was well established on DMF, which showed satisfied stability and selectivity in Hg sensing under high salinity condition, with the sensitivity of Hg²⁺ at the parts per billion level and total testing time less than 20s. With the advantages of being fast, amenable to automation and low cost, this device is promising for the formation of simple and rapid sensor device, especially for a routine monitoring and emergency detection of Hg/or other metals in coastal waters.