Arsenic Species In Water Samples Research Articles

One-step hot-press synthesis of amino functionalized Zr-based metal organic framework for determination and speciation of trace inorganic arsenic species in water samples with EDXRF spectrometry

Herein, amino functionalized Zr-based metal organic framework (UiO-66-NH2) on carbon cloth substrate was synthesized by using one-step hot-pressing method and the product (UiO-NH2@CC) was evaluated as a new solid phase extraction (SPE) material for determination and speciation of inorganic arsenic species (As(V) and As(III)) in water samples through energy dispersive X-ray fluorescence (EDXRF) spectrometry. SPE efficiency of UiO-NH2@CC was examined in batch and continuous adsorption (pre-concentration) processes and combination of either batch or continuous pre-concentration process with EDXRF spectrometry proposed analytical method, offering remarkable benefits (i.e., user-friendly, no elution procedure, environmentally friendly and cost-effective, etc.). Batch adsorption studies indicated that As(V) could be selectively adsorbed by UiO-NH2@CC at pH 2 and better represented by Freundlich isotherm model in 60 min of equilibrium time. Continuous adsorption studies at pH 2 demonstrated a drop in As(V) adsorption efficiency of UiO-NH2@CC for sample loading volume above 30 mL with increasing flow rate from 0.3 to 1.0 mL/min and initial As(V) concentration from 20 to 100 µg/L. By considering fortification experiments on real water samples at two levels (5 and 50 µg/L) of As(V) species, both batch and continuous pre-concentration steps coupled with EDXRF spectrometry, with LOD values of 0.790 and 0.220 µg/L, respectively, indicated good recoveries in the range of 87(±11)–104(±7) with no statistically significant differences. Finally, the continuous pre-concentration step followed by EDXRF measurement, as a representative analytical method, was of successful applicability to the speciation of As(III) and As(V) in real water samples with notable advantages (i.e., effortless, economical, practical and reproducible, etc.).

A simple and rapid copper-assisted microprecipitation method for the on-site separation of inorganic arsenic species in water samples followed by hydride generation atomic fluorescence spectrometry determination

A simple and rapid microprecipitation procedure was developed using copper (Cu2+) as precipitating agent for the separation–preconcentration of inorganic arsenic species (As(III) and As(V)) in waters prior to their determination by hydride generation atomic fluorescence spectrometry (HG-AFS). This procedure is based on selective precipitation of anionic species of As(V) with Cu2+, leaving neutral As(III) in the filtrate. The complexation of As(V) with Cu(II) entails the precipitation as copper arsenate, Cu3(AsO4)2 due to its low solubility product. The copper arsenate precipitate was characterized by XRD and EDS measurements. Optimum conditions for efficient microprecipitation process are; pH: 5 to 6, Cu/As mass ratio: 100, equilibration time: 2–3 min and eluent volume: 2 mL of 0.03 mol L−1 HCl. A fast process time of 2 min is enough for the on-site separation of As(III) and As(V) with the detection limits (LOD) 0.012 and 0.034 μg L−1 respectively. The recoveries were found to be in the range of 98–102%. This simple and fast method was successfully utilized for the on-site separation of As(III) and As(V) in wide variety of water samples collected in and around Kiradalli Tanda village, Karnataka state, India, where severe arsenic-contamination exists in various water bodies.

Determination and speciation of trace inorganic arsenic species in water samples by using metal organic framework mixed-matrix membrane and EDXRF spectrometry

A facile method to selectively determine trace As(V) species in the existence of As(III) one in water samples was developed, which was based on the batch adsorption process by using a miniaturized MIL-101(Fe) mixed-matrix membrane (MOF-MMM) followed by a direct determination through energy dispersive X-ray fluorescence (EDXRF) spectrometry. The quantitative adsorption of As(V) was achieved at pH (3–6) from 30 mL sample in 120 min of equilibrium time by employing the membrane with a monolayer adsorption capacity of Qo = 1.953 mg g−1. The direct determination of As(V) adsorbed on the membrane by EDXRF spectroscopy provided a method, not only easy-to-use and operable without elution stage, but also cost effective due to low gas consumption during the analysis. With a limit of detection of 0.094 μg L−1, analytical performance of the method, which was evaluated on fortified real water samples with three levels of As(V) (5, 10 and 50 μg L−1), demonstrated good recoveries in the range of 98(±3)-105(±10)%. Furthermore, the speciation of As(III) and As(V) in the fortified real samples containing other ionic species was also successfully achieved by described approach with characteristics of simple, cheap, viable and reproducible.

The amino - functionalized magnetic graphene oxide combined with graphite furnace atomic absorption spectrometry for determination of trace inorganic arsenic species in water samples

A novel adsorbent of magnetic graphene oxide (GO) chemically modified by cysteamine hydrochloride (Fe3O4@SiO2/GO-NH2) through thiol-ene click chemistry reaction was synthesized. The prepared Fe3O4@SiO2/GO-NH2 exhibit selective adsorption to As(V) with high adsorption capacity (52.66 mg g−1). Taking Fe3O4@SiO2/GO-NH2 as the adsorbents, a new method of magnetic solid phase extraction (MSPE) combined with graphite furnace atomic absorption spectrometry (GFAAS) was developed in determining trace-level inorganic arsenic species (As(III) and As(V)) in environmental water and bottled water samples. Various experimental parameters affecting the MSPE have been optimized. Under the optimal experimental parameters, the limit of detection of the established method for As(V) was 1.02 ng L−1, the relative standard deviations were 7.9% (intra-day, c = 50 ng L−1, n = 5) and 4.6% (inter-day, c = 50 ng L−1, n = 7), respectively, and the enrichment factor of the method was 392. GBW08666 and GBW08667 (certified reference material) were analyzed to confirm the accuracy of the method, and the results were matched well with the certified values. The established MSPE-GFAAS method was successfully applied in analyzing trace/ultratrace As(III) and As(V) in real water samples.

Capillary electrophoresis coupled to electrospray mass spectrometry for the determination of organic and inorganic arsenic compounds in water samples

Some compounds of arsenic are extremely toxic to the human body even at low levels. Long-term exposure from drinking contaminated water causes adverse health effects. This has led the European Union and other global organizations to reduce the maximum residue limit for the total arsenic up to 10 μg L−1 in water for human consumption. The toxicity of arsenic depends on the oxidation state, chemical structure and solubility in the biological environment. Main analytical procedures report on the determination of arsenic species in water samples which have been developed based on atomic spectroscopy –speciation performed in the sample treatment step– and inductively coupled plasma-mass spectrometry (ICP-MS). In such cases, speciation is performed by coupling to high-performance liquid chromatography (HPLC). As far as we know, the determination of arsenic species in water samples at low concentration levels by capillary electrophoresis (CE) coupled to electrospray mass spectrometry (ESI-MS) has not been described up to now. In this research CE-ESI(−)-MS is proposed for the identification and simultaneous quantification of organic and inorganic arsenic species in water samples for human consumption. The target compounds were dimethylarsinate (DMA), mono-methylarsonate (MMA), arsenite (i-As(III)) and arsenate (i-As(V)). Optimization of the composition and nature of both the electrophoretic separation medium –using hexafluoro-2-propanol (HFIP) as an additive– and the sheath liquid was performed and aimed at achieving the best sensitivity and separation efficiency for the CE-ESI(−)-MS coupling. Two simple sample treatments were proposed: one based on dispersive liquid-liquid micro-extraction (DLLME) intended for a rapid determination of the total content of inorganic arsenic in the water sample; and the second based on partial evaporation of the water sample to detect each of the four main arsenic species. For the second, limits of detection between 0.02 and 0.04 μg L-1 were found, which are similar results as the ones achieved with methods based on HPLC-ICP-MS.The DLLME + CE-ESI(−)-MS method was applied to the determination of total inorganic arsenic in eleven water samples in the province of Salamanca (Spain). Five of the analyzed samples had values close to, or superior to the maximum residue limit for the total of arsenic in water intended for human consumption (10 μg L-1). The validated method CE-ESI(−)-MS for arsenic speciation was applied with success to the analysis of the weakly mineralized water sample (dry residue < 50 mg L-1) of both groundwater and bottled water.

Vortex-assisted supramolecular solvent microextraction based on solidification of floating drop for preconcentration and speciation of inorganic arsenic species in water samples by molybdenum blue method

A new vortex-assisted supramolecular solvent microextraction based on solidification of floating drop (VA-SSM-SFD) has been developed for preconsentration and spectrophotometric determination of inorganic arsenic (iAs) species in various water samples. The method is based on the formation of arsenomolybdenium blue complex followed by VA-SSM-SFD procedure and subsequent spectrophotometric determination in a microcell. The supramolecular solvents consisted of reverse micelles of 1-dodecanol in tetrahydrofuran (THF) which were formed by in-situ coacervation of 1-dodecanol micelles in aqueous samples. Under optimized conditions, iAs (V) formed hetroploy blue complex and was directly determined. The concentration of iAs (III) was determined by subtracting iAs (III) from the total iAs following the oxidation of iAs (III) to iAs (V) by permanganate in acidic medium. Under optimal conditions, the calibration curve for iAs determination showed good linearity in the range of 5.0–140.0 μg L−1(R2 = 0.9988) and detection limit was found to be 0.4 μg L−1, which is much lower than WHO guideline of 10 μg L−1 for iAs in drinking water. The repeatability and reproducibility for 20 μg L−1 were found to be 2.47 and 3.9%, respectively. The proposed method was successfully applied to speciation of iAs species in real water samples.

Arsenic Speciation of Waters from the Aegean Region, Turkey by Hydride Generation: Atomic Absorption Spectrometry.

Arsenic in drinking water is a serious problem for human health. Since the toxicity of arsenic species As(III) and As(V) is different, it is important to determine the concentrations separately. Therefore, it is necessary to develop an accurate and sensitive method for the speciation of arsenic. It was intended with this work to determine the concentrations of arsenic species in water samples collected from Izmir, Manisa and nearby areas. A batch type hydride generation atomic absorption spectrometer was used. As(V) gave no signal under the optimal measurement conditions of As(III). A certified reference drinking water was analyzed by the method and the results showed excellent agreement with the reported values. The procedure was applied to 34 water samples. Eleven tap water, two spring water, 19 artesian well water and two thermal water samples were analyzed under the optimal conditions.

Cloud point extraction for trace inorganic arsenic speciation analysis in water samples by hydride generation atomic fluorescence spectrometry

A new cloud point extraction technique was established and used for the determination of trace inorganic arsenic species in water samples combined with hydride generation atomic fluorescence spectrometry (HGAFS). As(III) and As(V) were complexed with ammonium pyrrolidinedithiocarbamate and molybdate, respectively. The complexes were quantitatively extracted with the non-ionic surfactant (Triton X-114) by centrifugation. After addition of antifoam, the surfactant-rich phase containing As(III) was diluted with 5% HCl for HGAFS determination. For As(V) determination, 50% HCl was added to the surfactant-rich phase, and the mixture was placed in an ultrasonic bath at 70°C for 30min. As(V) was reduced to As(III) with thiourea–ascorbic acid solution, followed by HGAFS. Under the optimum conditions, limits of detection of 0.009 and 0.012μg/L were obtained for As(III) and As(V), respectively. Concentration factors of 9.3 and 7.9, respectively, were obtained for a 50mL sample. The precisions were 2.1% for As(III) and 2.3% for As(V). The proposed method was successfully used for the determination of trace As(III) and As(V) in water samples, with satisfactory recoveries.

Determination of ultra trace arsenic species in water samples by hydride generation atomic absorption spectrometry after cloud point extraction

Cloud point extraction (CPE) methodology has successfully been employed for the preconcentration of ultra-trace arsenic species in aqueous samples prior to hydride generation atomic absorption spectrometry (HGAAS). As(III) has formed an ion-pairing complex with Pyronine B in presence of sodium dodecyl sulfate (SDS) at pH 10.0 and extracted into the non-ionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-114). After phase separation, the surfactant-rich phase was diluted with 2 mL of 1 M HCl and 0.5 mL of 3.0% (w/v) Antifoam A. Under the optimized conditions, a preconcentration factor of 60 and a detection limit of 0.008 μg L −1 with a correlation coefficient of 0.9918 was obtained with a calibration curve in the range of 0.03–4.00 μg L −1. The proposed preconcentration procedure was successfully applied to the determination of As(III) ions in certified standard water samples (TMDA-53.3 and NIST 1643e, a low level fortified standard for trace elements) and some real samples including natural drinking water and tap water samples.

Development of an inexpensive and sensitive method for the determination of low quantity of arsenic species in water samples by CPE–FAAS

The simple and rapid preconcentration technique using cloud point extraction (CPE) was applied for the determination of As(V) and total inorganic arsenic (As(V) plus As(III)) in water samples by means of FAAS. As(V) has formed an ion-pairing complex with Pyronine B in the presence of cetyl pyridinium chloride (CPC) at pH 8.0 and extracted into the non-ionic surfactant Triton X-114, after centrifugation the surfactant-rich phase was separated and diluted with 1.0molL−1 HNO3 in methanol. The proposed method is very versatile and economic because it exclusively used conventional FAAS. After optimization of the CPE conditions, a preconcentration factor of 120, the detection and quantification limits of 1.67 and 5.06μgL−1 with a correlation coefficient of 0.9978 were obtained from the calibration curve constructed in the range of 5.0–2200μgL−1. The relative standard deviation, RSD as a measure of precision was less than 4.1% and the recoveries were in the range of 98.2–102.4%, 97.4–101.2% and 97.8–101.1% for As(V), As(III) and total As, respectively. The method was validated by the analysis of standard reference materials, TMDA-53.3 and NIST 1643e and applied to the determination of As(III) and As(V) in some real samples including natural drinking water and tap water samples with satisfactory results. The results obtained (34.70±1.08μgL−1 and 60.25±1.07μgL−1) were in good agreement with the certified values (34.20±1.38μgL−1 and 60.45±1.78μgL−1).

Preservation of arsenic species in water samples using phosphoric acid – Limitations and long-term stability

The preservation of arsenic species in water samples is an indispensable method to avoid their changes during storage, if it is not possible to analyse them immediately. The aim of this investigation was to demonstrate the limitations of the suggested method by using phosphoric acid as a preservation agent. The samples remain stable for 3 months, even if they show evidence of high concentrations of iron or manganese. Critical is an increasing pH > 3. Theoretically, a precipitation of strengite (Fe 3(PO 4) 2) could occur, which should be avoided. Phosphoric acid with a final concentration of 10 mM is recommended as a preservation agent, combined with keeping the samples cool (6 °C) and dark. Filtration of samples before preservation may be carried out with respect to the analytical aim to distinguish between the total and soluble fraction (without colloids). It was shown that filtered and non-filtered samples can be preserved by utilising the above mentioned scheme.

Application of natural zeolites for preconcentration of arsenic species in water samples.

Zeolites of the clinoptilolite type produced in Mexico and Hungary were investigated with respect to their sorption efficiency for various redox species of arsenic. Long-term experiments showed that arsenate remains stable for a long period in spiked deionised water and drinking water, as well as in the surface water of the Biela valley in Saxony, Germany. Both clinoptilolites are able to decrease the initial arsenic concentration of 200 microg l(-1) by more than 75% in deionised, drinking, ground and surface waters. In the case of the Mexican zeolite, both the arsenite and the arsenate concentrations (200 microg l(-1)) can be lowered from 200 microg l(-1) to 10 microg l(-1), which is the World Health Organisation's (WHO's) recommended maximum level. It was found that the presence of cations and anions in the natural waters of Biela, Germany, and Zimapán, Mexico, did not reduce the efficiency of the selected zeolites. The Hungarian zeolite removed 75% of the arsenate in the Zimapán water and only 50% when the sample was first acidified. This zeolite totally desorbed the fixed arsenic into a water volume that was half the volume in the adsorption experiment.

Speciation of selenium and arsenic compounds in natural waters by capillary zone electrophoresis after on-column preconcentration with field-amplified injection

A method for the separation and determination of selenium and arsenic compounds by capillary zone electrophoresis (CZE) was developed. On-column enrichment of selenium and arsenic was performed by stacking large volumes of samples injected onto the column with the field-amplified injection technique. Over a 100-fold preconcentration for selenium and arsenic compounds could be achieved within 3.7 min. This method was applied to the determination of selenium and arsenic species in real water samples. The detection limits were below 25 ppb. The relative standard deviations for the determination of selenium and arsenic species in water samples were in the range 4.0 to 15.6%.