Presence Of Arsenic Species Research Articles

Development of SiNWs based electrochemical sensor for trace level detection of arsenic

In the present study, we present a unique sensing platform relies on a silicon nanowire (SiNW) and reduced graphene oxide (rGO) hybrid nanostructure capped with (3-aminopropyl) triethoxysilane (APTES) and polyethylene glycol gold nanoparticle (PEG-AuNPs). Herein, MACE technique was applied to synthesize SiNWs, which was then used to develop a sandwich hybrid nanostructure by casting of rGO/APTES/PEG-AuNPs on its surface under room temperature and was characterised using various techniques. The developed PEG-AuNPs/rGO@APTES/SiNWs hybrid nanostructure-based sensing platform was used to detect two types of arsenic, that is, arsenite (As3+) and arsenate (As5+) using cyclic voltammetry in a sensitive and selective manner wherein the presence of arsenic species in real sample (blood) as well as standard samples was recorded.

Arsenosugar standards extracted from algae: Isolation, characterization and use for identification and quantification purposes

Sulfate (SO4-sug) and sulfonate (SO3-sug) arsenosugar standard solutions were obtained using preparative liquid chromatography. Several commercial algae samples were characterized (total contents and speciation) to select the most appropriate in relation to their arsenosugar contents. Water extracts from the selected sample (Fucus vesiculosus) were fractionated using a Hamilton PRP-X100 preparative column, and the presence of arsenic species in the isolated fractions was ascertained by IC-ICP-MS. Two of the fractions successfully presented only one arsenic species corresponding to sulfate and sulfonate arsenosugars at suitable concentrations. To unequivocally confirm the presence of both compounds, high-resolution mass spectrometry (ESI-TOF/MS) was used and the exact mass determined with errors lower than 0.5 ppm. The standard solutions obtained were successfully used to identify and quantify SO4-sug and SO3-sug in several edible algae samples purchased in local market. Total arsenic content for analyzed samples ranged from 34 to 57 mg kg−1, concentration values found for SO3-sug ranged from 5 to 36 mg As kg−1 and SO4-sug was only found in fucus with a concentration of 9.3 mg As kg−1.

A kinetic study of concurrent arsenic adsorption and phosphorus release during sediment resuspension

Combined phosphorus and arsenic pollution creates the possibility of interactive adsorption/desorption behavior due to the similar chemical structures of these two elements. The presence of arsenic species in overlying water can therefore affect phosphorus release during sediment resuspension, and vice versa. In this work, the adsorption kinetics of As(III) and As(V) on natural sediments during sediment resuspension were studied, as well as the release kinetics of phosphorus. Several environmental factors such as stirring rates, pH, and initial arsenic concentrations on arsenic sorption and phosphorus release were investigated. Results showed significant correlation between arsenic sorption amount and total phosphorus (TP) release (R2 = 0.9661 for As(III) and TP; R2 = 0.8336 for As(V) and TP). It was also shown that a higher sorption amount of either As(III) or As(V) led to a higher phosphorus release and that this effect was more pronounced for As(V) systems in both As(V) adsorption and TP release. Under phosphorus release-affected conditions, the As(III) and As(V) isotherms were well fitted by the Langmuir model (R2 = 0.9363 for As(III) and TP; R2 = 0.9251 for As(V) and TP). Acid and basic pH favors TP release and inhibits As(III) adsorption, whereas higher pH led to a decrease in As(V) adsorption. A higher stirring rate led to higher TP release, but its effect on arsenic adsorption was more complex. Arsenic adsorption kinetics all were well fitted by a pseudo-second-order model, but extreme pH conditions led to a different pattern for phosphorus release kinetics. These findings have significant implications for assessment and prediction of contaminant transportation in arsenic/phosphorus multicomponent contaminated systems.

Colorimetric As (V) detection based on S-layer functionalized gold nanoparticles

Herein, we present simple and rapid colorimetric and UV/VIS spectroscopic methods for detecting anionic arsenic (V) complexes in aqueous media. The methods exploit the aggregation of S-layer-functionalized spherical gold nanoparticles of sizes between 20 and 50nm in the presence of arsenic species. The gold nanoparticles were functionalized with oligomers of the S-layer protein of Lysinibacillus sphaericus JG-A12. The aggregation of the nanoparticles results in a color change from burgundy-red for widely dispersed nanoparticles to blue for aggregated nanoparticles. A detailed signal analysis was achieved by measuring the shift of the particle plasmon resonance signal with UV/VIS spectroscopy. To further improve signal sensitivity, the influence of larger nanoparticles was tested. In the case of 50nm gold nanoparticles, a concentration of the anionic arsenic (V) complex lower than 24ppb was detectable.

Chronic arsenic exposure increases TGFalpha concentration in bladder urothelial cells of Mexican populations environmentally exposed to inorganic arsenic

Inorganic arsenic (iAs) is a well-established carcinogen and human exposure has been associated with a variety of cancers including those of skin, lung, and bladder. High expression of transforming growth factor alpha (TGF-α) has associated with local relapses in early stages of urinary bladder cancer. iAs exposures are at least in part determined by the rate of formation and composition of iAs metabolites (MAs III, MAs V, DMAs III, DMAs V). This study examines the relationship between TGF-α concentration in exfoliated bladder urothelial cells (BUC) separated from urine and urinary arsenic species in 72 resident women (18–51 years old) from areas exposed to different concentrations of iAs in drinking water (2–378 ppb) in central Mexico. Urinary arsenic species, including trivalent methylated metabolites were measured by hydride generation atomic absorption spectrometry method. The concentration of TGF-α in BUC was measured using an ELISA assay. Results show a statistically significant positive correlation between TGF-α concentration in BUC and each of the six arsenic species present in urine. The multivariate linear regression analyses show that the increment of TGF-α levels in BUC was importantly associated with the presence of arsenic species after adjusting by age, and presence of urinary infection. People from areas with high arsenic exposure had a significantly higher TGF-α concentration in BUC than people from areas of low arsenic exposure (128.8 vs. 64.4 pg/mg protein; p < 0.05). Notably, exfoliated cells isolated from individuals with skin lesions contained significantly greater amount of TGF-α than cells from individuals without skin lesions: 157.7 vs. 64.9 pg/mg protein ( p = 0.003). These results suggest that TGF-α in exfoliated BUC may serve as a susceptibility marker of adverse health effects on epithelial tissue in arsenic-endemic areas.

Arsenic poisoning effects on cathodic polarization and hydrogen adsorption at platinum and steel electrodes in KF � 2HF melts

It is demonstrated how the presence of arsenic species in the KF · 2HF melt employed as the electrolyte in fluorine production cells greatly affects the electrocatalytic behaviour of the steel electrodes that are used as cathodes. Effects of the introduction of As2O3, AsF3 and AsF5 as the sources of catalyst poison species have been studied. Such species influence the electrode kinetics of the cathodic hydrogen evolution reaction (h.e.r.) and the adsorption of the overpotential-deposited (o.p.d.) H intermediate. Using Pt, as a model electrocatalyst surface, these effects were quantitatively studied by means of potential-relaxation transients, Tafel relations and cyclic voltammetry, the latter enabling changes of underpotential-deposited C (u.p.d.) H coverage due to the presence of As species to be evaluated. By means of simulation of the potential-relaxation behaviour, information on rate constants, coverages by o.p.d. H and As species were also derived. The presence of As at Pt cathodes suppresses the u.p.d. H adsorption and modifies the o.p.d. H behaviour and the associated pseudocapacitance. The presence and generation of As(−iii) species, as AsH3, in the evolved hydrogen gas was demonstrated by means of Marsh's test. The contact-angles of hydrogen bubbles generated in the h.e.r. at mild-steel electrode surfaces were also determined comparatively in relation to observed sluggish hydrogen bubble detachment from the electrode surfaces when As species were present.Ex situ XPS analysis confirmed the presence of As species on the electrode surface.