Bioaccumulation of antimony, arsenic, and mercury in the vicinities of a large antimony mine, China

To study the characteristics of antimony (Sb) bioaccumulation under high Sb background values, aquatic, amphibious and terrestrial biological samples were collected in the vicinity of the Xikuangshan (XKS) Sb mine area in China. Hydride generation-atomic fluorescence (HG-AFS) analysis showed that Sb concentrations in terrestrial invertebrates (average 30,400 μg kg^− 1 dry wt.) were higher than those in aquatic (average 5200 μg kg^− 1 dry wt.) and amphibian (average 2300 μg kg^− 1 dry wt.) biological samples. Within 1 km distance of the XKS Sb mine area, grasshoppers (Acrida chinensis) and earthworms (Pheretima aspergillum) had the highest Sb amounts of 17,300 ±3200 and 43,600 ± 47,700 μg kg^− 1 dry wt., respectively. No Sb biomagnifications were observed. The bioavailability of Sb was found to be lower than those of As and Hg. A preliminary conclusion is that antagonistic effects exist between Sb and Hg accumulation in biological samples from aquatic environments. Our study is the first to report such antagonistic effects between Sb and Hg. If this deduction proves to be correct, it should be taken into consideration in assessing human health risks, especially when Sb and Hg concentrations in the aquatic environments are high.     

Antimony distribution and mobility in rivers around the world's largest antimony mine of Xikuangshan, Hunan Province, China

Mining and smelting activities of the world largest Antimony (Sb) mine which is located at Xikuangshan area of Hunan Province, China, constitute important sources of Sb pollution throughout the rivers in or around the mine. Water samples show high levels of Sb (2-6384 µg/l) relative to the average concentration of the world rivers (1 µg/l) and it occurs mainly in oxidized form. Sb has a higher affinity for the particulate phase than for the aqueous phase. Its contents in sediments decreased along with the distance from the mine (from 7316 to 57 mg/kg) and had good correlation relationships (p < 0.001) with porewaters. In addition to the major pools in the Fe-Mn oxide (22.2-66.4%) and residual fractions (5.66-53.5%), Sb was relatively abundant in strongly adsorbed fraction. Laboratory experiments of the contaminated sediments show that with increasing amounts of Sb in the sediment, an increasing amount of Sb was leached and went into solution. Although Sb(V) was the predominant form, the release of Sb(III) in oxic conditions was also observed during laboratory experiments. And the amount of Sb released into solution was higher in anaerobic conditions than in oxygenated water.     

Simultaneous hyperaccumulation of arsenic and antimony in Cretan brake fern: Evidence of plant uptake and subcellular distributions

Arsenic (As) and antimony (Sb) show similar chemical properties and often present together in sulfide ores. Currently, phenomenon of co-contamination of As and Sb at some sites of the world has been increasingly emerged. The present study was conducted to explore the potential of Pteris cretica L. (Cretan brake fern), an arsenic (As) hyperaccumulator, to simultaneously accumulate As and Sb under hydroponic conditions. Arsenic was imposed at medium and high levels of 5 mg L^− 1 and 20 mg L^− 1, while Sb was imposed either single or co-presence with As at medium and high levels of 10 mg L^− 1 and 20 mg L^− 1, with no As and Sb addition as the control. The single and interactive effects of As and Sb on their uptake and subcellular distributions were analyzed. Cretan brake fern could accumulate high concentrations of As and Sb, with the highest concentrations of As and Sb been recorded as 1677.2 mg kg^− 1 and 1516.5 mg kg^− 1 in the fronds, respectively. Arsenic and Sb were found mainly in cytosol, while less in cell wall and cytoplasmic organelles. Sb uptake by Cretan brake fern was enhanced with increasing As levels, which was accompanied with an increase of Sb but a decrease of As in cytosol fractions. Arsenic uptake was slightly enhanced whereas suppressed when Sb was co-present in a medium and high level, respectively; however, in both conditions, As was found to be decreased in cytosol of the above ground parts as fronds and stems of Cretan brake fern. The results demonstrate Cretan brake fern can simultaneously hyperaccumulate As and Sb, thus is valued in phytoremediation of As and Sb co-contamination.     

Study of antimony (III) binding to soil humic acid from an antimony smelting site

Soil samples were collected from an antimony smelting site in Guangxi Zhuang Autonomous Region, China, at four locations characterized by different land usage, including two cultivated sites: one formerly cultivated and one uncultivated. Surface soils from all four sites were heavily polluted by toxic metals including antimony (Sb), lead (Pb) and arsenic (As), and their concentrations were 410-3330 mg·kg⁻¹, 410-3690 mg·kg⁻¹ and 200-460 mg·kg⁻¹, respectively. In the uncultivated area metal levels were 1.4-6.2 times higher as compared to the formerly and currently agriculture land. Lower levels at the cultivated sites may have resulted from an accumulation of airborne particles by vegetation and lower contents in the surface soil. However, the elevated mercury (Hg) content may reflect both natural and anthropogenic origins in this smelting site. Soil-derived humic acid (HA) from the smelting site reacted directly with Sb (III) aqueous solutions with concentrations of 12, 71 and 143 mg·g⁻¹. The maximum Sb (III) binding to the soil-derived HA was 253 μmol·g⁻¹ (added concentration of 71 mg·g⁻¹) and showed more binding (up to 50%) at lower Sb content.     

Speciation analysis of antimony in marine biota by HPLC-(UV)-HG-AFS: Extraction procedures and stability of antimony species

Speciation analysis of antimony in marine biota is not well documented, and no specific extraction procedure of antimony species from algae and mollusk samples can be found in the literature. This work presents a suitable methodology for the speciation of antimony in marine biota (algae and mollusk samples). The extraction efficiency of total antimony and the stability of Sb(III), Sb(V) and trimethylantimony(V) in different extraction media (water at 25 and 90 °C, methanol, EDTA and citric acid) were evaluated by analyzing the algae Macrosystis integrifolia (0.55 ± 0.04 μg Sb g⁻¹) and the mollusk Mytilus edulis (0.23 ± 0.01 μg Sb g⁻¹). The speciation analysis was performed by anion exchange liquid chromatography (post-column photo-oxidation) and hydride generation atomic fluorescence spectrometry as detection system (HPLC-(UV)-HG-AFS). Results demonstrated that, based on the extraction yield and the stability, EDTA proved to be the best extracting solution for the speciation analysis of antimony in these matrices. The selected procedure was applied to antimony speciation in different algae samples collected from the Chilean coast. Only the inorganic Sb(V) and Sb(III) species were detected in the extracts. In all analyzed algae the sum of total antimony extracted (determined in the extracts after digestion) and the antimony present in the residue was in good agreement with the total antimony concentration determined by HG-AFS. However, in some extracts the sum of antimony species detected was lower than the total extracted, revealing the presence of unknown antimony species, possibly retained on the column or not detected by HPLC-(UV)-HG-AFS. Further work must be carried out to elucidate the identity of these unknown species of antimony.     

Simultaneous determination of trace arsenic(III), antimony(III), total arsenic and antimony in Chinese medicinal herbs by hydride generation-double channel atomic fluorescence spectrometry

A new method was developed for simultaneous determination of trace arsenic and antimony in Chinese herbal medicines by hydride generation-double channel atomic fluorescence spectrometry with a Soxhlet extraction system and an n-octanol-water extraction system, respectively. The effects of analytical conditions on the fluorescence intensity were investigated and optimized. A water-dissolving and methanol-water-dissolving capability were compared. The contents of different species in five Chinese herbal medicines and their decoctions were analyzed. The concentration ratios of n-octanol-soluble As or Sb to water-soluble As or Sb were related to the kinds of medicine and the acidity of the decoction. Soxhlet extraction was found to be an effective method for plants pretreatment for determination of arsenic and antimony species in Chinese herbs; the interferences of coexisting ions were evaluated. The proposed method has the advantages of simple operation, high sensitivity and high speed, with 3σ detection limits of 0.094 μg g⁻¹ for As(III), 0.056 μg g⁻¹ for total As, 0.063 μg g⁻¹ for Sb(III) and 0.019 μg g⁻¹ for total Sb in a 1.0 g of the sample.     

The use of silver nanoparticles as an effective modifier for the determination of arsenic and antimony by electrothermal atomic absorption spectrometry

Silver nanoparticles (AgNPs) were proposed as a new chemical modifier for the elimination of interferences when determining arsenic and antimony in aqueous NaCl or Na₂SO₄ solutions and in sea-water by electrothermal atomic absorption spectrometry. For this purpose, the AgNPs were prepared simply by reducing silver nitrate with sodium citrate. The effects of pyrolysis and atomization temperatures and the amounts of interferents and modifiers on the sensitivities of these elements were investigated. In the presence of the proposed modifier, a pyrolysis temperature of at least 1100 °C for arsenic and 900 °C for antimony could be applied without the loss of analytes, and the interferences were greatly reduced to allow for interference-free determination. The detection limits (N = 10, 3σ) for arsenic and antimony were 0.022 ng and 0.046 ng, respectively. AgNPs are cheaper and more available compared to many other modifiers. No background was detected, and the blank values were negligible.     

Simultaneous determination of antimony(III) and antimony(V) by UV-vis spectroscopy and partial least squares method (PLS)

This paper describes a procedure for the speciation of antimony by UV-vis spectroscopy using pyrogallol as complexing agent. A partial least squares (PLS) regression was performed to resolve highly overlapping spectrophotometric signals obtained from mixtures of Sb(III) and Sb(V). The relative error in absolute value was less than 5% when concentrations of several mixtures were calculated. The minimum concentration determined was 3.96 × 10⁻⁵ mol dm⁻³ and 3.98 × 10⁻⁵ mol dm⁻³ for Sb(V) and Sb(III), respectively. The analysis of the possible effect of the presence of foreign ions in the solution was performed and the procedure was successfully applied to the speciation of antimony in pharmaceutical preparations and aqueous samples.     

Anodic stripping voltammetry of antimony using gold nanoparticle-modified carbon screen-printed electrodes

Carbon screen-printed electrodes (CSPE) modified with gold nanoparticles present an interesting alternative in the determination of antimony using differential pulse anodic stripping voltammetry. Metallic gold nanoparticles deposits have been obtained by direct electrochemical deposition. Scanning electron microscopy measurements show that the electrochemically synthesized gold nanoparticles are deposited in aggregated form. Any undue effects caused by the presence of foreign ions in the solution were also analyzed to ensure that common interferents in the determination of antimony by ASV. The detection limit for Sb(III) obtained was 9.44 × 10⁻¹⁰ M. In terms of reproducibility, the precision of the above mentioned method in %R.S.D. values was calculated at 2.69% (n = 10). The method was applied to determine levels of antimony in seawater samples and pharmaceutical preparations.     

Speciation of antimony by adsorptive stripping voltammetry using pyrogallol

This paper describes a new procedure for the determination of Sb (III) and Sb (V) by differential pulse adsorptive stripping voltammetry (DPAdSV) using pyrogallol as a complexing agent. The selection of the experimental conditions was made using experimental design methodology. The detection limits obtained were 1.03 × 10⁻¹⁰ and 9.48 × 10⁻⁹ mol dm⁻³ for Sb (III) and Sb (V), respectively.In order to carry out the simultaneously determination of both antimony species a partial least squares regression (PLS) is employed to resolve the voltammetric signals from mixtures of Sb (III) and Sb (V) in the presence of pyrogallol. The relative error in absolute value is less than 0.5% when concentrations of several mixtures are calculated. Moreover, the solution is analyzed for any possible effects of foreign ions. The procedure is successfully applied to the speciation of antimony in pharmaceutical preparations and water samples.     

Development and characterization of ion selective electrode for the assay of antimony

The construction and general performance characteristics of two novel potentiometric carbon paste electrodes (CPE) responsive to antimony are described. These sensors are based on the use of the ion associate complexes of tetraiodoantimonate (TIA) anion with cetylpyridinium (CP) and triphenyl tetrazolium (TPT) counter cations as ion exchange site in a carbon paste matrix. The two sensors exhibits fast, stable and near-Nernstian for the mono charged TIA anion over the concentration range 1 × 10⁻³ to 10⁻⁶ M at 25 °C in the pH range 4-10 with anionic slope of 58.0 ± 0.5 and 55.0 ± 0.7 per concentration decade for TIA-CP and TIA-TPT, respectively. The lower detection limits are 4 and 5 × 10⁻⁶ M and response time are 20 and 30 s in the same order of both electrodes. Selectivity coefficients for antimony relative to a number of different cations and anions were investigated. There is negligible interference from many inorganic cation and anion except for Hg²⁺, Cd²⁺, and Bi³⁺; however, their effect were eliminated by EDTA. The determination of 1.0-120.0 μg/ml of antimony in aqueous solutions shows an average recovery of 99.0 and 97.5% with relative standard deviation of 2.0% for both electrodes at 40 μg/ml. The determination of antimony in wastewater and some antibilharzial compounds using the proposed electrodes gave results that compare favorably with those obtained by the atomic absorption spectrometric method. Precipitation titrations involving cetylpyridinium chloride as titrant are monitored with both electrodes with inflection point of 180 and 100 mV for TIA-CP and TIA-TPT, respectively.     

Flow analysis-hydride generation-gas phase derivative molecular absorption spectrophotometric determination of antimony in oral homeopathic products ("AntimoniumTartaricum") formulated under alcoholic medium

In this work, a flow analysis-hydride generation-gas phase derivative molecular absorption-(UV) spectrophotometric method has been developed for the direct determination of antimony in aqueous and hydro-alcoholic samples. Antimony (III) from undiluted samples is directly transformed into the gaseous stibine (SbH₃) form by on-line reaction with sodium tetrahydroborate (NaBH₄) in acidic medium (HCl). The gaseous phase generated is separated from the liquid phase using a commercial gas-liquid separator, and swept - with the help of a carrier gas (N₂) stream - into a quartz gas cell (10 cm pathlength); where the corresponding absorption spectrum is acquired in a continuous mode over the 190-300 nm wavelength range, using a conventional spectrophotometer. A derivative strategy was selected in order to avoid the strong spectral interference of the ethanol vapor on the gaseous SbH₃ absorption spectrum. In this way, the peak height at 223 nm of the second order derivative spectrum appears as a clear, clean and interference free analytical signal, which allows the direct determination of antimony. The recovery values obtained from homeopathic formulations (prepared in alcoholic medium) spiked with know amounts of antimony ranged between 97.5 and 103%. The method provides a dynamic range from 0.20 to 30 mg Sb l⁻¹. The precision (RDS), evaluated by replicate analysis (n = 5) of samples and standard solution containing between 2.5 and 15 mg Sb l⁻¹ was in all cases lower than 1.2%. The proposed method was applied to the determination of antimony in commercial homeopathic products (“Antimonium Tartaricum”) prepared in hydro-alcoholic medium; and showed to be simple, precise, and accurate.     

The atomic absorption determination of antimony,arsenic, bismuth, cadmium, lead, and tin in iron, copper,and zinc alloys with the graphite furnace

Antimony, arsenic, bismuth, cadmium, lead, and tin can be determined in metallurgical samples by flame atomic absorption spectrometry at levels of 0.005 wt%, but lower concentrations frequently necessitate preconcentration. The graphite furnace allows determination of these elements at concentrations 1–2 orders of magnitude lower than is possible with flame techniques. All six elements have detection limits at or below 1μg g⁻¹ in a variety of alloys. Calibration for antimony and load was done with standards containing the principal component of the alloy as a synthetic matrix. Bismuth, cadmium, and tin could be determined accurately only by the standard addition method. Arsenic could be determined in iron alloys with synthetic standards, but standard additions were required for copper alloys.     

Development of analytical method for determination of Sb(V), Sb(III) and TMSb(V) in occupationally exposed human urine samples by HPLC-HG-AFS

In the present paper, we develop a methodology for antimony speciation in occupationally exposed human urine samples by high-performance liquid chromatography with hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS). The methodology was applied to the determination of Sb(V), Sb(III) and (CH₃)₃SbCl₂ (TMSb(V)). Retention time of Sb(V), Sb(III) and TMSb(V) species were 0.88, 2.00 and 3.61 and the detection limits were 0.18, 0.19 and 0.12 μg L^− 1, for 100 μL loop injection respectively which is considered useful for elevated/occupationally exposed urine samples. Studies on the stability of antimony species in urine samples on the function of the elapsed time of preservation (4 °C) and storage (− 70 °C) were performed. Results revealed that antimony species are highly unstable at − 70 °C, probably due to co-precipitation reaction. In this kind of matrix transformation during preservation time may occur, such as oxidation of Sb(III) to Sb(V) and transformation into species that do not elute from the column. EDTA shows that it is able to stabilize Sb(III) for more than one week of preservation time at 4 °C avoiding co-precipitation during storage at − 70 °C. Finally the methodology was applied to occupationally exposed human urine samples. 25% of specimens present antimony levels (Sb(V)) of more than 5 μg L^− 1.     

化学蒸气发生-四通道原子荧光光谱法同时测定高纯金中的痕量As,Sb,Bi,Te

采用化学蒸气发生-四通道原子荧光光谱法测定了高纯金中的痕量砷、锑、铋和碲。用乙酸乙脂萃取分离金,水相还原后采用化学蒸气发生-四通道原子荧光光谱法测定高纯金中的痕量砷、锑、铋和碲。在最佳条件下,方法对As,Sb,Bi,Te的检出限分别为0.04,0.05,0.04,0.03 ng/mL(3σ);测定精密度分别为0.98,0.89,0.94,0.99%(对10 ng/mL As,Sb,Bi和Te混合标准,n=7)。方法对实际样品中的As,Sb,Bi,Te进行了同时测定,测定结果与标准方法无明显差异,各元素的加标回收率为95%～105%。     

Inter-element interferences in the determination of arsenic and antimony by hydride generation atomic absorption spectrometry with a quartz tube atomizer

The interferences between arsenic and antimony on each other during the hydride generation atomic absorption spectrometry (HGAAS) determination of arsenic and antimony using a quartz tube atomizer (QTA) were examined. In order to eliminate or reduce such interferences by selective heat decomposition of arsine and stibine, a Pyrex adsorption U-tube trap containing glass wool was placed between the drying tube and the quartz tube atomizer. Although at 250 °C stibine decomposes and is held almost completely by the trap, arsine is also decomposed to an extent of 24% and, therefore, thermal decomposition is not useful to eliminate antimony interference on arsenic determination. The effect of coating the glass wool in the U-tube with antimony on the arsenic suppression of the antimony signal was studied. The results showed that the antimony coating in the U-tube could not hold arsenic effectively and its interference on the antimony signal could not be eliminated by this means. In the second part of the study, oxygen was supplied to the quartz tube atomizer during atomization in order to study the effect of supplying oxygen on the antimony signal and on the interference of arsenic in the antimony determination. Sensitivity was increased in the presence of oxygen and interferences of arsenic on antimony determination was decreased by about 10% when oxygen was supplied. It was also observed that the extent of interferences depended mainly on the interferent concentration rather than the analyte concentration.     

Determination of major antimony species in seawater by continuous flow injection hydride generation atomic absorption spectrometry

The capabilities and limitations of the continuous flow injection hydride generation technique, coupled to atomic absorption spectrometry, for the speciation of major antimony species in seawater, were investigated. Two pre-concentration techniques were examined. After continuous flow injection hydride generation and collection onto a graphite tube coated with iridium, antimony was determined by graphite furnace atomic absorption spectrometry. The low detection limits obtained (∼5 ng l⁻¹ for Sb(III) and ∼10 ng l⁻¹ for Sb(V) for 2.5 ml seawater samples) permitted the determination of Sb(III) and total antimony in seawater with the use of selective hydride generation and on-line UV photooxidation. The number of samples that can be analyzed is about 15 per hour for Sb(III) determinations and 10 per hour for total antimony determinations. The analysis of seawater samples showed that Sb(V) was the predominant species, even in the presence of important biological activity.     

Simultaneous determination of inorganic and organic antimony species by using anion exchange phases for HPLC-ICP-MS and their application to plant extracts of Pteris vittata

Antimony is a common contaminant at abandoned sites for non-ferrous ore mining and processing. Because of the possible risk of antimony by transfer to plants growing on contaminated sites, it is of importance to analyze antimony and its species in such biota. A method based on high performance liquid chromatographic separation and inductively coupled plasma mass spectrometric detection (HPLC-ICP-MS) was developed to determine inorganic antimony species such as Sb(III) and Sb(V) as well as possible antimony-organic metabolisation products of the antimony transferred into plant material within one chromatographic run. The separation is performed using anion chromatography on a strong anion exchange column (IonPac AS15/AG 15). Based on isocratic optimizations for the separation of Sb(III) and Sb(V) as well as Sb(V) and trimenthylated Sb(V) (TMSb(V)), a chromatographic method with an eluent gradient was developed. The suggested analytical method was applied to aqueous extracts of Chinese break fern Pteris vittata samples. The transfer of antimony from spiked soil composites into the fern, which is known as a hyperaccumulator for arsenic, was investigated under greenhouse conditions. Remarkable amounts of antimony were transferred into roots and leaves of P. vittata growing on spiked soil composites. Generally, P. vittata accumulates not only arsenic (as shown in a multiplicity of studies in the last decade), but also antimony to a lower extent. The main contaminant in the extracts was Sb(V), but also elevated concentrations of Sb(III) and TMSb(V) (all in μg L⁻¹ range). An unidentified Sb compound in the plant extracts was detected, which slightly differ in elution time from TMSb(V).     

Inter-method comparison for the determination of antimony and arsenic in peat samples

Four analytical approaches, based on different physical principles, for the determination of antimony (Sb) and arsenic (As) in ancient peat samples were critically evaluated: (a) open vessel digestion/hydride generation-atomic absorption spectrometry (HG-AAS), (b) closed-pressurized digestion in a microwave oven followed by sector field-inductively coupled plasma-mass spectrometry (SF-ICP-MS), (c) digestion in a microwave autoclave and subsequent quadrupole-inductively coupled plasma-mass spectrometry (Q-ICP-MS) measurements and (d) instrumental neutron activation analysis (INAA). The quality control scheme applied, always included the use of adequate plant reference materials to ensure the accuracy and precision of the analytical procedures. Additionally, two internal peat reference materials were analyzed using all four analytical approaches, generally showing good agreement for both elements. Method detection limits for As and Sb provided by all procedures were approximately 5 and 2 ng g⁻¹ which is sufficiently low for the reliable quantification of both elements in ancient, pre-anthropogenic peat samples. A comparison of As and Sb concentrations in a set of peat samples determined by INAA, HG-AAS and SF-ICP-MS revealed that INAA underestimated the values in a systematic manner, whereas HG-AAS and SF-ICP-MS data agreed very well. Best precision of the results was obtained by analytical procedures involving HG-AAS or Q-ICP-MS and varied from 3.6 to 4.3% and 7.1 to 7.5% for As (at about 0.5 μg g⁻¹) and Sb (at about 0.1 μg g⁻¹), respectively. The highest sample throughput (40 samples per run accomplished in 2 h) combined with low risk of sample contamination could be realized in the high-pressure microwave autoclave. The amount of sample required by all approaches was 200 mg, except for INAA which needed at least 25 times more sample mass to achieve comparable detection limits. For the quantification of As and Sb, inductively coupled plasma-mass spectrometry (ICP-MS) was preferred over INAA and HG-AAS, mainly because (a) less sample is needed and (b) As and Sb can be determined simultaneously. In addition, ICP-MS offers the possibility to measure concurrently a wide range of other elements which also are of environmental interest.     

Simultaneous speciation of inorganic arsenic and antimony in water samples by hydride generation-double channel atomic fluorescence spectrometry with on-line solid-phase extraction using single-walled carbon nanotubes micro-column

A new method was developed for the simultaneous speciation of inorganic arsenic and antimony in water by on-line solid-phase extraction coupled with hydride generation-double channel atomic fluorescence spectrometry (HG-DC-AFS). The speciation scheme involved the on-line formation and retention of the ammonium pyrrolidine dithiocarbamate complexes of As(III) and Sb(III) on a single-walled carbon nanotubes packed micro-column, followed by on-line elution and simultaneous detection of As(III) and Sb(III) by HG-DC-AFS; the total As and total Sb were determined by the same protocol after As(V) and Sb(V) were reduced by thiourea, with As(V) and Sb(V) concentrations obtained by subtraction. Various experimental parameters affecting the on-line solid-phase extraction and determination of the analytes species have been investigated in detail. With 180 s preconcentration time, the enrichment factors were found to be 25.4 for As(III) and 24.6 for Sb(III), with the limits of detection (LODs) of 3.8 ng L^− 1 for As(III) and 2.1 ng L^− 1 for Sb(III). The precisions (RSD) for five replicate measurements of 0.5 μg L⁻¹ of As(III) and 0.2 μg L⁻¹ of Sb(III) were 4.2 and 4.8%, respectively. The developed method was validated by the analysis of standard reference materials (NIST SRM 1640a), and was applied to the speciation of inorganic As and Sb in natural water samples.