Microcolumn sorption of antimony(III) chelate for antimony speciation studies

Selective sorption of the Sb(III) chelate with ammonium pyrrolidine dithiocarbamate (APDC) on a microcolumn packed with C₁₆-bonded silica gel phase was used for the determination of Sb(III) and of total inorganic antimony after reducing Sb(V) to Sb(III) by l-cysteine. A flow injection system composed of a microcolumn connected to the tip of the autosampler was used for preconcentration. The sorbed antimony was directly eluted with ethanol into the graphite furnace and determined by AAS. The detection limit for antimony was significantly lowered to 0.007 μg l⁻¹ in comparison to 1.7 μg l⁻¹ for direct injection GFAAS. This procedure was applied for speciation determinations of inorganic antimony in tap water, snow and urine samples. For the investigation of long-term stability of antimony species a flow injection hydride generation atomic absorption spectrometry with quartz tube atomization (FI HG QT AAS) and GFAAS were used for selective determination of Sb(III) in the presence of Sb(V) and total content of antimony, respectively. Investigations on the stability of antimony in several natural samples spiked with Sb(III) and Sb(V) indicated instability of Sb(III) in tap water and satisfactory stability of inorganic Sb species in the presence of urine matrix.     

Over‐Oxidized Poly (Phenol Red) Film Modified Glassy Carbon Electrode for Anodic Stripping Voltammetric Determination of Ultra‐Trace Antimony (III)

In this study, we introduce a very sensitive and selective method for the differential pulse anodic stripping determination of Sb(III) ion on the over‐oxidized poly(phenol red) modified glassy carbon electrode (PPhRed_ox/GCE) in 0.1 mol L^‐1 HCl medium. The formation of both poly(phenol red) and over‐oxidized poly(phenol red) film on the electrode surfaces were characterized by electrochemical impedance spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy techniques. An anodic stripping peak of Sb(III) was observed at 0.015 V on the PPhRed_ox/GCE. Higher anodic stripping peak current of Sb(III) was obtained at PPhRed_ox/GCE compared with both bare GCE and poly(phenol red) film modified GCE (PPhRed/GCE). The calibration graph consisted of two linear segments of 0.044 ‐ 1.218 μg L⁻¹ and 3.40 – 18.26 μg L⁻¹ with a detection limit of 0.0075 μg L⁻¹. The proposed over‐oxidized polymer film modified electrode was applied successfully for the analysis of antimony in different spiked water samples. Spiked recoveries for water samples were obtained in the range of 93.0–103.0%. The accuracy of the method was also verified through the analysis of standard reference materials (SCP SCIENCE‐EnviroMAT™ EP−L‐2).     

Development of a non-chromatographic method for the speciation analysis of inorganic antimony in mushroom samples by hydride generation atomic fluorescence spectrometry

A simple and sensitive method has been developed for the direct determination of toxic species of antimony in mushroom samples by hydride generation atomic fluorescence spectrometry (HG AFS). The determination of Sb(III) and Sb(V) was based on the efficiency of hydride generation employing NaBH₄, with and without a previous KI reduction, using proportional equations corresponding to the two different measurement conditions. The extraction efficiency of total antimony and the stability of Sb(III) and Sb(V) in different extraction media (nitric, sulfuric, hydrochloric, acetic acid, methanol and ethanol) were evaluated. Results demonstrated that, based on the extraction yield and the stability of extracts, 0.5 mol L^− 1 H₂SO₄ proved to be the best extracting solution for the speciation analysis of antimony in mushroom samples. The limits of detection of the developed methodology were 0.6 and 1.1 ng g^− 1 for Sb(III) and Sb(V), respectively. The relative standard derivation was 3.8% (14.7 ng g^− 1) for Sb(V) and 5.1% (4.6 ng g^− 1) for Sb(III). The recovery values obtained for Sb(III) and Sb(V) varied from 94 to 106% and from 98 to 105%, respectively. The method has been applied to determine Sb(III), Sb(V) and total Sb in five different mushroom samples; the Sb(III) content varied from 4.6 to 11.4 ng g^− 1 and Sb(V) from 14.7 to 21.2 ng g^− 1. The accuracy of the method was confirmed by the analysis of a certified reference material of tomato leaves.     

Determination of traces of Sb(III) using ASV in Sb-rich water samples affected by mining

Chemical speciation [Sb(V) and Sb(III)] affects the mobility, bioavailability and toxicity of antimony. In oxygenated environments Sb(V) dominates whereas thermodynamically unstable Sb(III) may occur. In this study, a simple method for the determination of Sb(III) in non acidic, oxygenated water contaminated with antimony is proposed. The determination of Sb(III) was performed by anodic stripping voltammetry (ASV, 1–20 μg L⁻¹ working range), the total antimony, Sb(tot), was determined either by inductively coupled plasma mass spectrometry (ICP-MS, 1–100 μg L⁻¹ working range) or inductively coupled plasma optical emission spectrometry (ICP-OES, 100–10,000 μg L⁻¹ working range) depending on concentration. Water samples were filtered on site through 0.45 μm pore size filters. The aliquot for determination of Sb(tot) was acidified with 1% (v/v) HNO₃. Different preservatives, namely HCl, L(+) ascorbic acid or L(+) tartaric acid plus HNO₃, were used to assess the stability of Sb(III) in synthetic solutions.The method was tested on groundwater and surface water draining the abandoned mine of Su Suergiu (Sardinia, Italy), an area heavily contaminated with Sb. The waters interacting with Sb-rich mining residues were non acidic, oxygenated, and showed extreme concentrations of Sb(tot) (up to 13,000 μg L⁻¹), with Sb(III) <10% of total antimony. The stabilization with L(+) tartaric acid plus HNO₃ appears useful for the determination of Sb(III) in oxygenated, Sb-rich waters. Due to the instability of Sb(III), analyses should be carried out within 7 days upon the water collection. The main advantage of the proposed method is that it does not require time-consuming preparation steps prior to analysis of Sb(III).     

Uptake and excretion of total inorganic arsenic by the freshwater alga Chlorella vulgaris

Arsenic-tolerant freshwater alga Chlorella vulgaris which had been collected from an arsenicpolluted environment were tested for uptake and excretion of inorganic arsenic. Approximately half the quantity of arsenic taken up by C. vulgaris was estimated to be adhered to the extraneous coat (10 wt %) of the cell. The remainder was bioaccumulated by the cell. Both adhered and accumulated arsenic concentrations increased with an increase in arsenic(V) concentration of the aqueous phase. Arsenic(V) accumulation was affected by the growth phse: arsenic was most actively accumulated when the cell was exposed to arsenic during the early exponential phase and then accumulation decreased with an increase in culture time exposed to arsenic. The alga grew well in the modified Detmer (MD) medium containing 1 mg As(III) dm^?3 and the growth curve was approximated by a ‘logistic equation’. Arsenic(III) was accumulated up to the second day of the culture time and arsenic(III) accumulation decreased with an increase in the culture time after that. Arsenic accumulation was also largely affected by various nutrients, especially by managanese, iron and phosphorus compounds. A modified MD medium with the three nutrients was proposed for the purpose of effective removal of arsenic from the aqueous phase. Using radioactive arsenate (Na₂H⁷⁴AsO₄), the arsenic accumulated was found to be readily excreted under conditions which were unfavourable for the multiplication of C. vulgaris.     

The association mode of arsenic accumulated in the freshwater alga Chlorella vulgaris

Arsenic accumulated in living Chlorella vulgaris cells was solvent-fractionated with chloroform/methanol (2:1), and the fractions were analyzed for arsenic. A large part of the accumulated arsenic was localized in the extract residues. The extract residue from the same extraction of C. vulgaris, which had been, however, cultured in any arsenic-free Detmer medium (MD), adsorbed arsenic physico-chemically at a concentration of 1.1 mg As g^?1 dry weight. Arsenic was found to be combined with protein with molecular weight around 3000 in the arsenicaccumulated living cells. The arsenic-bound protein was analyzed for amino acids. The experimental results showed that no metallothionein-like protein was inductively biosynthesized in C. vulgaris on the exposure to arsenic.     

Speciation Analysis of Antimony (III) and Antimony (V) by Flame Atomic Absorption Spectrometry After Separation/Preconcentration With Cloud Point Extraction

A sensitive and simple method for flame atomic absorption spectrometry (FAAS) determination of antimony species after separation/preconcentration by cloud point extraction (CPE) has been developed. When the system temperature is higher than the cloud point extraction temperature, the complex of antimony (III) with N-benzoyl-N-phenyhydroxylamine (BPHA) can enter the surfactant-rich phase, whereas the antimony (V) remains in the aqueous phase. Antimony (III) in surfactant-rich phase was analyzed by FAAS and antimony (V) was calculated by subtracting of antimony (III) from the total antimony after reducing antimony (V) to antimony (III) by L-cysteine. The main factors affecting the cloud point extraction, such as pH, concentration of BPHA and Triton X-114, equilibration temperature and time, were investigated systematically. Under optimized conditions, the detection limits (3σ) were 1.82 ng mL⁻¹ for Sb(III) and 2.08 ng mL⁻¹ for Sb(total), and the relative standard deviations (RSDs) were 2.6% for Sb(III) and 2.2% for Sb(total). The proposed method was applied to the speciation of antimony species in artificial seawater and wastewater, and recoveries in the range of 95.3–106% were obtained by spiking real samples. This technique was validated by means of reference water materials and gave good agreement with certified values.     

Determination of trace concentrations of antimony by the introduction of stibine into an inductively-coupled plasma for atomic emission spectrometry

A simple, rapid and sensitive method is described for the determination of trace concentrations of antimony by inductively-coupled plasma atomic emission spectrometry with hydride generation. Hydrochloric acid (1 M) is the best medium for stibine generation, but antimony(III) is also effectively reduced to stibine in 1 M malic acid or 0.5 M tartaric acid, whereas antimony(V) gives no significant signal in either of these acids. This permits the differential determination of Sb(III) and Sb(V). Most of the inter-element interference effects can be minimized by thiourea, bur standard additions are recommended for accurate determinations. Thiourea is also effective in prereducing Sb(V) to Sb(III). The detection limit is 0.19 ng Sb ml^?1 and the calibration graph is linear up to 100 μg ml^?1. The r.s.d, at 1 and 100 ng Sb ml^?1 are 3.8 and 2.1%, respectively. The method is applied to copper metal and to speciation of antimony in waste water.     

Evaluation of continuous hydride generation combined with helium and argon microwave induced plasmas using a surfatron for atomic emission spectrometric determination of arsenic,antimony and selenium

The direct coupling of continuous hydride generation with both Ar and He microwave induced plasmas (MIP) sustained in a surfatron has been optimized for the simultaneous determination of arsenic, antimony and selenium with atomic emission spectrometry. While a discharge tube of quartz was found suitable for the Ar plasma, the use of an Al₂O₃ tube led to improved performance of the He plasma. The He MIP was found to be less tolerant to the introduction of hydrogen than the Ar MIP, and correspondingly the hydride generation should be operated at a lower flow rate of 0.5% NaBH₄ solution. The introduction of the H₂O vapour produced during hydride generation into both discharges was found to greatly decrease the sensitivities and to degrade the measurement precision. It could be effectively removed with trapping by concentrated H₂SO₄. The detection limits (3σ) for As, Sb and Se are 1, 0.4 and 1 ng ml⁻¹ with the Ar MIP, and 2, 0.3 and 6 ng ml⁻¹ with the He MIP, respectively. The calibration curves are linear over three decades of concentration. The mutual interferences from As(III), Sb(III), Se(IV), Bi(III) and Sn(IV) were found to be negligible at interferent concentrations below 1 μg ml⁻¹ and in most cases the tolerable interferent concentrations are up to 20 μg ml⁻¹. The proposed method has been applied to the determination of As, Sb and Se in tea samples at μg g⁻¹ levels.     

Chemical Speciation of Antimony(III and V) in Water by Adsorptive Cathodic Stripping Voltammetry Using the 4‐(2‐Thiazolylazo) – Resorcinol

A simple adsorptive cathodic stripping voltammetry method has been developed for antimony (III and V) speciation using 4‐(2‐thiazolylazo) – resorcinol (TAR). The methodology involves controlled preconcentration at pH 5, during which antimony(III) – TAR complex is adsorbed onto a hanging mercury drop electrode followed by measuring the cathodic peak current (I_p,c) at ?0.39 V versus Ag/AgCl electrode. The plot of I_p,c versus antimony(III) concentration was linear in the range 1.35×10^?9–9.53×10^?8 mol L^?1.The LOD and LOQ for Sb(III) were found 4.06×10^?10 and 1.35×10^?9 mol L^?1, respectively. Antimony(V) species after reduction to antimony(III) with Na₂SO₃ were also determined. Analysis of antimony in environment water samples was applied satisfactorily.     

Speciation of antimony(III) and antimony(V) in cell extracts by anion chromatography/ inductively coupled plasma mass spectrometry

An analytical method for the separation and quantification of Sb(III) and Sb(V) using anion chromatography with ICP-MS is presented. The optimum conditions for the separation of the antimony species were established with 15 mmol/L nitric acid at pH 6 as eluent system on a PRP-X100 column. The retention times for antimony(V) and antimony(III) were 85 s and 300 s with detection limits of 0.06 μg/L and 0.29 μg/L, respectively. The proposed method was applied to cell extracts of Leishmania donovani, which were incubated with antimony(III) and antimony(V). Some metabolism seemed to occur within the cells.     

The spectrophotometric determination of antimony in water,effluents, marine plants and silicates

A spectrophotometric procedure is described for the determination of antimony in natural waters (including sea water and effluents), algae and silicates. After a preliminary oxidative digestion for waters, or acid attack for algae and silicates, the element is quantitatively coprecipitated at pH 5.0 with hydrous zirconium oxide. The precipitate is dissolved in acid, and, after reduction with titanium(III) chloride, antimony is oxidized to antimony(V) with sodium nitrite. The ion pair of the SbCl₆^- ion with crystal violet is extracted with benzene and its absorbance is measured at 610 nm (molar absorptivity 74,000 l mol^-1 cm^-1). Extraction with toluene causes some loss of sensitivity. The detection limit is 0.005 μg l^-1; relative standard deviations are 0.5% and 1.1% for spiked distilled water (0.5 μg l^-1) and sea water (0.26 μg l^-1), respectively. A wide range of anions and cations cause no interference at levels many times those in natural waters. The technique can be adapted for application to marine algae and silicates; relative standard deviations are 1.8% and 2% for samples of Pelvetia canaliculata (0.19 μg Sb g^-1) and a Pacific Ocean red clay (1.08 μg Sb g^-1), respectively. Results for the U.S. Geological Survey Standard rocks GSP1 (2.7 ppm) and DTS1 (0.53 ppm) are in good agreement with those of earlier workers.     

Speciation of Antimony by Adsorptive Stripping Voltammetry Using Pyrogallol Red

This paper proposes a procedure for the speciation of antimony by Differential Pulse Adsorptive Stripping Voltammetry (DPAdSV) using pyrogallol red (PGR) as a complexing agent. It employs a Partial Least Squares regression (PLS) in the resolution of strongly overlapping voltammetric signals obtained from mixtures of Sb(III) and Sb(V) in the presence of pyrogallol red. The absolute value of the relative error was less than 3.5% when concentrations of several mixtures were calculated, the minimum concentrations being 9.98×10^?9 mol dm^?3 and 4.87×10^?8 mol dm^?3 for Sb(III) and Sb(V), respectively. Any undue effects caused by the presence of foreign ions in the solution were also analyzed. The procedure was successfully applied to the speciation of antimony in pharmaceutical preparations.     

Construction and Evaluation of a Gold Tubular Electrode for Flow Analysis: Application to Speciation of Antimony in Water Samples

A tubular gold electrode (TGE) is described for the first time by summarizing the important aspects of its construction and evaluation. Applicability of the TGE is evaluated in the speciation of Sb(III) and Sb(V) using anodic stripping voltammetry in a single flow manifold. Studies with surface active interferences and metallic cations were performed. The proposed conditions for antimony determination showed good tolerance towards cationic, anionic and nonionic surface active substances. A linear response for antimony was obtained for solutions containing significant amounts of several metallic cations. Linear calibration curves for Sb(III) were obtained in the range 1–10 ppb with a detection limit of 0.19 ppb (CV=2.91%, n=5, [Sb(III)]=5 ppb). For Sb(V), linear calibration curves were in the range 1–15 ppb with a detection limit of 0.32 ppb (CV=1.41%, n=5, [Sb(V)]=5 ppb). The figures of merit achieved sustain for the good applicability of the proposed method as it allows the determination of antimony at levels below maximum values permitted in consuming waters. Results of antimony concentration determined in water samples were validated against the ICP‐MS reference procedure or compared with reference water samples.     

Speciation analysis of inorganic antimony in soil using HPLC-ID-ICP-MS

Speciation analysis of Sb(III) and Sb(V) in a soil sample was performed through extraction and on-line isotope dilution concentration determination after a chromatographic separation. The total Sb concentration found in a through traffic contaminated soil sample was (4.17 μg g⁻¹, 0.3 μg g⁻¹ SD, n=6). It was determined using ICP-MS after soil digestion using the sodium peroxide sintering method. The optimized extraction procedure for speciation analysis was carried out using 100 mmol L⁻¹ citric acid at pH 2.08 by applying an ultrasonic bath for 45 min at room temperature. The effects of citric acid concentration (0–500 mmol L⁻¹), pH (1–6), and temperature (30–60°C) on inorganic antimony species distribution in the examined sample were studied and optimized. The separation of Sb(III) and Sb(V) was achieved using an anion exchange column (PRP-X100) and 10 mmol L⁻¹ EDTA and 1 mmol L⁻¹ phthalic acid at pH 4.5 as a mobile phase. The eluent from the HPLC was mixed with an enriched (94.2%) ¹²³Sb spike solution that was pumped by a peristaltic pump with a constant flow rate (0.5 mL min⁻¹) in a three-way valve. The blend passed directly to the Conikal nebulizer of the ICP-MS. By using the above extraction procedure and methodology, 43.2% Sb(V) (2.9% RSD, n=3) and 6.0% Sb(III) (1.3% RSD, n=3) of total Sb found in the sample could be detected. The detection limits achieved by the proposed method were 20 ng L⁻¹ and 65 ng L⁻¹ for Sb(V) and Sb(III), respectively. The precision, evaluated by using RSD with 100 ng L⁻¹ calibration solutions, was 2.7% and 3.2% (n=6) for Sb(V) and Sb(III), respectively, in aqueous solutions.     

Solid phase chelating extraction and separation of inorganic antimony species in pharmaceutical and water samples for graphite furnace atomic absorption spectrometry

A separation procedure for antimony(III) and antimony(V) was developed with the use of chelating celluloses. Sb(III) was separately pre-concentrated on imino diacetic acid–ethyl cellulose in the acidic pH range, in which the uptake of Sb(V) was negligible in the μg L^− 1 concentration range. On the other hand, both Sb species Sb(V) and Sb(III) were pre-concentrated on a chloride form of 2,2′-diaminodiethylamine-cellulose. These solid phase extraction procedures were combined with graphite furnace atomic absorption spectrometry (SPE–GFAAS) for Sb detection. Pharmaceutical compounds of organic and inorganic types (ten compounds), as well as mineral water samples (twelve types) were analyzed. Detection limits of 0.18 µg L^− 1 Sb(III) and 0.25 µg L^− 1 Sb(V) were found in aqueous sample solutions and water samples, respectively, considering a 25-fold pre-concentration. The total Sb, mostly in the form of Sb(V), could be determined in phosphate-containing pharmaceuticals, while in phosphoric acid, Sb(III) was the dominant form. In all other types of samples the Sb content was below the detection threshold, and therefore, the potential suitability of the SPE–GFAAS method for the determination of Sb(III) species was proven by recovery tests of spiked samples. This method ensures the required detection power with regard to the allowable Sb limits established by international organizations.     

Ion-Selective Electrodes for the Determination of Antimony and Thallium Based on Water-Insoluble Basic Dye Salts

Abstract

Hexachloroantimonate(V) and tetrachlorothallate(III) salts of Sevron Red L (C.I. Basic Red 17), Sevron Red GL (C.I. 11,085), Flavinduline O (C.I. 50,000) and Phenazinduline O have been applied in liquid-state ion-selective electrodes for the determination of antimony and thallium. The slope of potential versus pM graphs approach full Nernstian response in the range 10 M (Sb) and 10^?6 M (T1) to 10^?2 M. An unusual feature of the electrodes is their response to antimony(III) as well as to antimony(V).     

Inversvoltammetrische spurenbestimmung von Antimon(III) und Antimon(V) in aquatischen umweltproben nach selektiver extraktionStripping Voltammetry of Traces of Antimony(III) and Antimony(V) in Natural Waters After Selective Extraction

The biological activity of antimony depends on the oxidation state. The Sb(III) and Sb(V) states can be distinguished, even in the ng l^?1 range, by coupling extraction with ammonium pyrrlidenedithiocarbamate into methyl isobutyl ketone (APDC/MIBK), or N-benzoyl-N-phenylhydroxylamine (BPHA) into chloroform, with anodic stripping voltammetry (a.s.v.). After complex formation with APDC in acetate-buffered medium, Sb(III), but not Sb(V), is extracted into MIBK and quantified by a.s.v. Antimony(V) is quantified in the aqueous phase after removal of Sb(III) by extraction with BPHA into chloroform from the medium acidified with nitric acid. The applicability of the proposed separation/a.s.v. method is demonstrated for samples of rain, snow and water from a dredging operation. The stability of the two antimony species is examined for natural waters with Sb(III) and Sb(V) added; possibilities of stabilization are described. The precedures should be suitable for speciation of antimony in relatively unpolluted waters.     

Determination of total antimony(III,V) by square-wave anodic stripping voltammetry with in situ plated bismuth-film electrode

A sensitive and reliable method is described for the determination of total Sb(III,?V) at traces levels by Osteryoung square-wave anodic stripping voltammery (OSWASV). This method is based on the co-deposition of Sb(III,?V) with Bi(III) onto an edge-plane pyrolytic graphite substrate at an accumulation step. OSWASV studies indicated that the co-deposited antimony was oxidised with anodic scans to give an enhanced anodic peak at about 450?mV vs. Ag/AgCl (sat. KCl). The anodic stripping peak current was directly proportional to the total concentration of antimony in the ranges of 0.01–0.10?µg?L^?1, 0.10–1.0?µg?L^?1 and 1.0–18.0?µg?L^?1 with correlation coefficient higher than 0.995 when 2.0?mol?L^?1 hydrochloric acid was used. The detection limits calculated as S/N?=?3 was 5.0?ng?L^?1 in 2.0?mol?L^?1 hydrochloric acid at 180?s deposition time. The relative standard deviation was 5% (n?=?6) at 0.10?µg?L^?1 level of antimony. The analytical results demonstrate that the proposed method is applicable to analyses of real water samples.