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).     

Study on simultaneous speciation of arsenic and antimony by HPLC-ICP-MS

A method was developed for the simultaneous speciation of arsenic and antimony with HPLC-ICP-MS using C30 reversed phase column. Eight kinds of arsenic compounds (As(III), As(V), monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA), arsenobetaine (AB), arsenocholine (AsC), trimethylarsine oxide (TMAO) and tetramethylarsonium (TeMA)), Sb(III) and Sb(V) were simultaneously separated by the special mobile phase containing ammonium tartrate. Especially for the species of organic As, a C30 column was better than a C18 column in the effect of separation. Limits of detection (LOD) for these elements were 0.2 ng ml⁻¹ for the species of each As, and 0.5 ng ml⁻¹ for the species of each Sb, when a 10 μl of sample was injected, respectively. The proposed method was applied to a hot spring water and a fish sample.     

Speciation of arsenic(III) and arsenic(V) by inductively coupled plasma-atomic emission spectrometry coupled with preconcentration system

A novel and simple flow-based method was developed for the simultaneous determination of As(III) and As(V) in freshwater samples. Two miniature columns with a solid phase anion exchange resin, placed on two 6-way valves were utilized for the solid-phase collection/concentration of arsenic(III) and arsenic(V), respectively. As(III) could be retained on the column after its oxidation to As(V) species with an oxidizing agent. The collected analytes were then sequentially eluted by 2 M nitric acid and introduced into ICP-AES. Potassium permanganate was examined as potential oxidizing agent for conversion of As(III) to As(V). The standard deviation of the analytical signals (peak height) for the replicate analysis (n = 5) of 0.5 μg l⁻¹ solution were 3 and 5% for As(III) and As(V), respectively. The limit of detection (3σ) for both As(III) and As(V) were 0.1 μg l⁻¹. The proposed system produced satisfactory results on the application to the direct analysis of inorganic arsenic species in freshwater samples.     

Speciation analysis of inorganic Sb(III) and Sb(V) ions by using mini column filled with Amberlite XAD-8 resin

The speciation of inorganic Sb(III) and Sb(V) ions in aqueous solution was studied. The adsorption behavior of Sb(III) and Sb(V) ions were investigated as iodo and ammonium pyrollidine dithiocarbamate (APDC) complexes on a column filled with Amberlite XAD-8 resin. Sb(III) and Sb(V) ions were recovered quantitatively and simultaneously from a solution containing 0.8 M NaI and 0.2 M H₂SO₄ by the XAD-8 column. Sb(III) ions were also adsorbed quantitatively as an APDC complex, but the recovery of the Sb(V)-APDC complex was found to be <10% at pH 5. According to these data, the concentrations of total antimony as Sb(III)+Sb(V) ions and Sb(III) ion were determined with XAD-8/NaI+H₂SO₄ and XAD-8/APDC systems, respectively. The Sb(V) ion concentration was calculated by subtracting the Sb(III) concentration found with XAD-8/APDC system from the total antimony concentration found with XAD-8/NaI+H₂SO₄ system. The developed method was applied to determine Sb(III) and Sb(V) ions in samples of artificial seawater and wastewater.     

Antimony(V) volatilization with bromide and determination by inductively coupled plasma atomic emission spectrometry

Antimony(V) is volatilized by reaction with potassium bromide in concentrated sulfuric acid media. After volatilization, the gases can be transported to an inductively coupled plasma spectrometer for atomic emission of antimony and its analytical determination. The influent factors, concentrated sulfuric acid volume, concentration and volume of the potassium bromide aqueous solution and carrier gas flow were investigated and optimized using different alternatives. A detection limit of 48 ng ml⁻¹ of Sb was achieved under the optimized conditions with a precision of 7.6% and the calibration graph was linear from 0.10 to 10.0 μg ml⁻¹ for a sample injection of 130 μl.The study of interferences from common cations and anions revealed a good tolerance for most ions, although there was a significant improvement in Sb(V) volatility when As(III) was present. Furthermore, the As(III) sensitization was only produced with Sb(V) species, while the volatility of the Sb(III) bromide species was unaltered.The method was applied to the determination of Sb in real river waters. The results were checked using alternative atomic spectroscopy methods.     

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).     

Synthetic Iowaite Can Effectively Remove Inorganic Arsenic from Marine Extract

For the removal of arsenic from marine products, iowaite was prepared and investigated to determine the optimal adsorption process of arsenic. Different chemical forms of arsenic (As(III), As(V)) with varying concentrations (0.15, 1.5, 5, 10, 15, and 20 mg/L) under various conditions including pH (3, 5, 7, 9, 11) and contact time (1, 2, 5, 10, 15, 30, 60, 120, 180 min) were exposed to iowaite. Adsorption isotherms and metal ions kinetic modeling onto the adsorbent were determined based on Langmuir, Freundlich, first- and second-order kinetic models. The adsorption onto iowaite varied depending on the conditions. The adsorption rates of standard solution, As(III) and As(V) exceeded 95% under proper conditions, while high complexity was noted with marine samples. As(III) and As(V) from Mactra veneriformis extraction all decreased when exposed to iowaite. The inclusion morphology and interconversion of organic arsenic limit adsorption. Iowaite can be efficiently used for inorganic arsenic removal from wastewater and different marine food products, which maybe other adsorbent or further performance of iowaite needs to be investigated for organic arsenic.     

Speciation of antimony by atomic absorption spectrometry. Applicability to selective determination of Sb(III) and Sb(V) in liquid samples and of bioavailable antimony in sediments and soil samples

A comparative study was made of several methods to speciale Sb(III) and Sb(V) by AAS: 1) Selective extraction of Sb(III) with lactic acid/malachite green graphite furnace-AAS, 2) Sb(III) and total antimony determination by hydride generation-AAS coupled to flow injection, batch, and continuous flow systems. These methods were applied to determine total antimony and Sb(III) in sea and surface water and total antimony in sediments and in soil. For soils different sample pretreatments were used: HNO₃-H₂SO₄-HC1O₄, HF-HNO₃-H₂SO₄-HC1O₄, cold aqua regia and slurry formation procedures in water and 4M HC1. In each case the recovery of total antimony and the ability to selective determine Sb(III) were studied. The detection limits obtained were 0.01 ng, 0.07 ng, 2.97 ng and 0.21 ppb for GF-AAS, FIA-HG-AAS, HG (Batch)-AAS, and HG (continuous flow)-AAS, respectively.     

Simultaneous speciation of inorganic arsenic and antimony in natural waters by dimercaptosuccinic acid modified mesoporous titanium dioxide micro-column on-line separation and inductively coupled plasma optical emission spectrometry determination

A novel absorbent was prepared by dimercaptosuccinic acid chemically modifying mesoporous titanium dioxide and was employed as the micro-column packing material for simultaneous separation/preconcentration of inorganic arsenic and antimony species. It was found that both trivalent and pentavalent of inorganic As and Sb species could be adsorbed quantitatively on dimercaptosuccinic acid modified TiO₂ within a pH range of 4–7, and only As(III) and Sb(III) could be quantitatively retained on the micro-column within a pH range of 10–11 while As(V) and Sb(V) were passed through the micro-column without the retention. Based on this fact, a new method of flow injection on-line micro-column separation/preconcentration coupled to inductively coupled plasma optical emission spectrometry was developed for simultaneous speciation of trace inorganic arsenic and antimony in natural waters. Under the optimized conditions, an enrichment factor of 10 and sampling frequency of 10 h^− 1 were obtained with on-line mode. The detection limits of As(III), As(V), Sb(III), and Sb(V) are 0.53, 0.49, 0.77 and 0.71 ng mL^− 1 for on-line mode and as low as 0.11, 0.10, 0.15 and 0.13 ng mL^− 1 for off-line mode due to its higher enrichment factor (50), respectively. The relative standard deviations of two modes are less than 6.7% (C = 20 ng mL^− 1, n = 7). The concentration ratio of lower oxidation states/higher oxidation states changing from 1:10 to 10:1 has no obvious effect on the recoveries of As(III) and Sb(III). In order to validate the developed method, two certified reference materials of GSBZ5004-88 and GBW(E)080545 water sample were analyzed and the determined values are in good agreement with the certified values. The proposed method was successfully applied to the simultaneous speciation of inorganic arsenic and antimony in natural waters.     

Sorption of As(V) from waters using chitosan and chitosan-immobilized sodium silicate prior to atomic spectrometric determination

A natural biosorbent containing amine functional groups, chitosan, and a novel sorbent, chitosan-immobilized sodium silicate, were prepared and utilized for the selective sorption of As(V) from waters prior to its determination by atomic spectrometric techniques, namely, hydride generation atomic absorption spectrometry (HGAAS) and inductively coupled plasma mass spectrometry (ICP-MS). Chitosan was synthesized from chitin and sodium silicate was used as the immobilization matrix due to its straightforward synthesis. Through sequential sorption studies, it was shown that chitosan-immobilized sodium silicate has exhibited a better chemical stability than the chitosan itself which demonstrates the advantage of immobilization method. Both chitosan and chitosan-immobilized sodium silicate were shown to selectively adsorb As(V), arsenate, from waters at pH 3.0 at which neither chitin nor sodium silicate displayed any sorption towards As(V). The sorption of arsenate by chitosan is supposed to have electrostatic nature since pH of 3.0 is both the point at which the amino groups in chitosan are protonated and also the predominant form of As(V) is H₂AsO₄⁻. A pre-oxidation step is required if both As(III) and As(V) are to be determined. Desorption from the sorbents was realized with 1.0% (w/v) l-cysteine prepared in a pH 3.0 solution adjusted with HCl. Among the possible interfering species tested, only Te(IV) and Sb(III) were shown to cause a decrease in the sorption capacity especially at high interferant concentrations. High concentrations of Sb(III) also resulted in gas phase interference during hydride generation.The validity of the method was checked both via spike recovery experiments and also through the analysis of a standard reference material. Spike recovery tests were carried out with four different types of water; namely, ultra-pure, bottled drinking, tap, and sea water; and percent recovery values were found to be 114 (±4), 112 (±2), 43 (±4), and 0 (±1), respectively. It was concluded that the proposed methodology can be applied efficiently to low-to-medium ionic strength solutions, such as most drinking waters. The accuracy of the method was additionally investigated through the analysis of a standard reference material and a good correlation was found between the determined (26.6 ± 2.4 μg L⁻¹) and the certified (26.67 μg L⁻¹) value.     

Solid-phase extraction (SPE) assays to ascertain the mechanisms of retention of antimony species in several stationary phases

Liquid chromatography is the most suitable technique for antimony speciation in several types of samples. However, efficiency can be poor for some of these peaks, especially Sb(III) and Me₃SbCl₂ (TMSb). Weak and strong anion exchange stationary phases are mainly used for antimony speciation in several chromatographic conditions. The present study examines the possible contribution of the interaction between antimony species (Sb(III), Sb(V) and TMSb) and stationary phase support to the overall retention mechanism in their chromatographic separation. Several SPE cartridges, selected from those mainly used as support in anion exchange columns, were assayed. Sb (V) was quantitatively eluted from the PSDVB (polystyrene divinylbenzene) and SiO₂ phases, showing the absence of interaction. Sb (III) showed some interaction with the PSDVB phase; TMSb showed strong retention with all the cartridges studied and it was only eluted from the PSDVB phase.     

Extremely efficient electro-Fenton-like Sb(III) detoxification using nanoscale Ti-Ce binary oxide: An effective design to boost catalytic activity via non-radical pathway

Environmental risks posed by discharge of the emerging contaminant antimony (Sb) into water bodies have raised global concerns recently. The toxicity of Sb has been shown to be species-dependent, with Sb(III) demonstrating much greater toxicity than Sb(V). Here, we proposed an electrochemical filtration system to achieve rapid detoxification of Sb(III) via a non-radical pathway. The key to this technology was an electroactive carbon nanotube filter functionalized with nanoscale Ti-Ce binary oxide. Under an electric field, in situ generated H₂O₂ could react with the Ti-Ce binary oxide to produce hydroperoxide complexes, which enabled an efficient transformation of Sb(III) to the less toxic Sb(V) (τ < 2 s) at neutral pH. The impact of important operational parameters was assessed and optimized, and system efficacy could be maintained over a wide pH range and long-term operation. An optimum detoxification efficiency of> 90% was achieved using lake water spiked with Sb(III) at 500 μg/L. The results showed that Ti/Ce-hydroperoxo surface complexes were the dominant species responsible for the non-radical oxidation of Sb(III) based on extensive experimental evidences and advanced characterizations. This study provides a robust and effective strategy for the detoxification of water containing Sb(III) and other similar heavy metal ions by integrating state-of-the-art advanced oxidation processes, electrochemistry and nano-filtration technology.     

Non-chromatographic speciation of toxic arsenic in fish

A rapid, sensitive and economic method has been developed for the direct determination of toxic species of arsenic present in fish and mussel samples. As(III), As(V), dimethylarsinic acid (DMA), and monomethylarsonic acid (MMA) were determined by hydride generation-atomic fluorescence spectrometry using a series of proportional equations without the need of a chromatographic previous separation. The method is based on the extraction of arsenic species from fish through sonication with HNO₃ 3 mol l⁻¹ and 0.1% (m/v) Triton and washing of the solid phase with 0.1% (m/v) EDTA, followed by direct measurement of the corresponding hydrides in four different experimental conditions. The limit of detection of the method was 0.62 ng g⁻¹ for As(III), 2.1 ng g⁻¹ for As(V), 1.8 ng g⁻¹ for MMA and 5.4 ng g⁻¹ for DMA, in all cases expressed in terms of sample dry weight. The mean relative standard deviation values (R.S.D.) in actual sample analysis were: 6.8% for As(III), 10.3% for As(V), 8.5% for MMA and 7.4% for DMA at concentration levels from 0.08 mg kg⁻¹ As(III) to 1.3 mg kg⁻¹ DMA. Recovery studies provided percentages greater than 93% for all species in spiked samples. The analysis of SRM DORM-2 and CRM 627 certified materials evidenced that the method is suitable for the accurate determination of arsenic species in fish.     

Extraction of arsenic species from airborne particulate filters—Application to an industrial area of Greece

In the present study, the extraction of the arsenic species arsenite (As(III)), arsenate (As(V)), monomethyarsonic (MMA) and dimethylarsinic acid (DMA) from airborne particulate filters was investigated and optimized. For this purpose, total suspended particulate matter as well as size fractionated aerosol samples were collected from the industrial area of Aspropyrgos, Greece, in glass fibre and polycarbonated filters, respectively. Among H₃PO₄ and HCl, tested in various concentrations, concentrated HCl was found to be the most effective extractant for arsenic from both polycarbonated and glass fibre filters, without provoking any arsenic species transformation. However, the quantitative extraction of arsenic species from glass fibre filters required the subsequent washing of the filters with ultrapure water after their leaching with concentrated HCl. The developed procedure was applied to airborne particulate filters for arsenic speciation in Aspropyrgos' atmosphere. The results showed an enrichment of As in the fine (PM_2.5) compared with the coarse (PM_10–2.5) fraction of airborne particulates, while As(V) was found to be the predominant arsenic species in all samples. Finally, As concentration in the PM₁₀ fraction, for the investigated area and time period from December 2004 to June 2006, was below the target value of 6 ng As m^− 3, referred in the Directive 2004/107 of European Union.     

Simultaneous determination of inorganic As(III), As(V), Sb(III), Sb(V), and Se(IV) species in natural waters by APDC/MIBK-NAA

A solvent extraction preconcentration as well as separation method involving ammonium pyrrolinedithiocarbamate (APDC) and 4-methyl-2-pentanone (MIBK) in conjunction with neutron activation analysis (NAA) was developed for the simultaneous measurement of low levels of inorganic arsenic, antimony and selenium species in natural waters. Several critical factors affecting the APDC/MIBK-NAA method were studied in detail including the selection of chelating agent, solvent, aqueous pH for the extraction of six species as well as a few organoarsenic species as representatives for organic species, the stability of the complexes in organic phase, phase volume ratios for extraction and back-extraction steps, and the reduction of the species from higher to lower oxidation state. The detection limits for arsenic, antimony and selenium were found to be as low as 0.026, 0.010 and 0.12 μg L^?1, respectively. Trace amounts of As(III), As(V), Sb(III), Sb(V), and Se(IV) in different types of natural water sample and two water certified reference materials were measured using the APDC/MIBK-NAA method.     

On-line separation and preconcentration of inorganic arsenic and selenium species in natural water samples with CTAB-modified alkyl silica microcolumn and determination by inductively coupled plasma-optical emission spectrometry

A new, simple, and selective method has been presented for the separation and preconcentration of inorganic arsenic (As(III)/As(V)) and selenium (Se(IV)/Se(VI)) species by a microcolumn on-line coupled with inductively coupled plasma-optical emission spectrometry (ICP-OES). Trace amounts of As(V) and Se(VI) species were separated and preconcentrated from total As and Se at desired pH values by a conical microcolumn packed with cetyltrimethylammonium bromide (CTAB)-modified alkyl silica sorbent in the absence of chelating reagent. The species adsorbed by CTAB-modified alkyl silica sorbent were quantitatively desorbed with 0.10 ml of 1.0 mol l⁻¹ HNO₃. Total inorganic arsenic and selenium were similarly extracted after oxidation of As(III) and Se(IV) to As(V) and Se(VI) with KMnO₄ (50.0 μmol l⁻¹). The assay of As(III) and Se(IV) were based on subtracting As(V) and Se(VI) from total As and total Se, respectively. All parameters affecting the separation/preconcentration of As(V) and Se(VI) including pH, sample flow rate and volume, eluent solution and volume have been studied. With a sample volume of 3.0 ml, the sample throughput was 24 h⁻¹ and the enrichment factors for As(V) and Se(VI) were 26.7 and 27.6, respectively. The limits of detection (LODs) were 0.15 μg l⁻¹ for As(V) and 0.10 μg l⁻¹ for Se(VI). The relative standard deviations (RSDs) for nine replicate determinations at 5.0 μg l⁻¹ level of As(V) and Se(VI) were 4.0% and 3.6%, respectively. The calibration graphs of the method for As(V) and Se(VI) were linear in the range of 0.5–1000.0 μg l⁻¹ with a correlation coefficient of 0.9936 and 0.9992, respectively. The developed method was successfully applied to the speciation analysis of inorganic arsenic and selenium in natural water samples with satisfactory results.     

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.     

Removal of As(III) and As(V) by natural and synthetic metal oxides

The removal properties of As(III) and As(V) by the several metal oxides having different mineral type and content of metals were investigated in batch and column reactors. The used metal oxides were Fe-oxide loaded sand (ILS), Mn-oxide loaded sand (MLS), activated alumina (AA), sericite (SC) and iron sand (IS). From the pH-edge adsorption experiments with AA and ILS, maximum As(III) adsorption was observed around neutral pH while As(V) adsorption was followed an anionic-type behavior. Among five metal oxides, AA showed the greatest removal capacity for both As(III) and As(V) through adsoption process but it has little oxidation capacity for As(III). Eventhough IS had much greater content of Fe-oxides than ILS, it showed a relatively lower removal capacity for both As(III) and As(V). This result suggests that adsorption of arsenic onto metal oxides is controlled by not only the contents of Fe-oxides but also mineral type of Fe-oxides. Column tests were performed at different combinations of metal oxides in a column reactor to find the best column system, which effectively treat both As(III) and As(V) at the same time. Among several combinations, the column reactors packed with MLS-AA and MLS-ILS showed a near complete oxidation of As(III) by MLS for a long time and the greatest adsorption of total arsenic compared to the column reactor packed with MLS-IS.     

Developments with anion exchange stationary phases for HPLC-ICP-MS analysis of antimony species

Novel HPLC-ICP-MS methodologies are developed using strong anion exchange (Phenomenex SAX-SB) and weak anion exchange (Alltec HAAX) stationary phases in conjunction with a range of aqueous mobile phases to enable simultaneous separations of inorganic Sb(III), Sb(V) and organic trimethylantimony dichloride (TMSb) species in synthetic solutions. Optimum isocratic separations of inorganic Sb(V) and Sb(III) species are achieved using mobile phases comprised of ammonium tartrate under controlled pH conditions, and rapid pH gradient elution profiles are developed to facilitate separations of the Sb(V), Sb(III) and TMSb species in a single chromatographic run. Optimum peak resolution is achieved when using the 100 x 4.6 mm HAAX column at 20 degrees C and 100 mM ammonium tartrate mobile phases with a gradient from pH 3.0 to pH 1.2, although a system peak co-elutes with TMSb under these conditions and precludes quantitative analyses. Interestingly, the elution order of Sb(V), Sb(III) and TMSb species reverses when the temperature of the HAAX stationary phase is increased to 60 degrees C, and concurrent use of a less acidic pH gradient elution profile from pH 2.3 to pH 1.5 is shown to enable successful species separations whilst preventing occurrence of the co-eluting system peak. Limits of detection are achieved in the sub ng mL(-1) range using these novel HPLC-ICP-MS methodologies and provide scope for future environmental analysis applications.     

Speciation of very low amounts of arsenic and antimony in waters using dispersive liquid–liquid microextraction and electrothermal atomic absorption spectrometry

A new procedure for the determination of inorganic arsenic (III,V) and antimony (III,V) in water samples by dispersive liquid–liquid micro extraction separation and electrothermal atomic absorption spectrometry (ETAAS) is presented. At pH 1, As(III) and Sb(III) are complexed with ammonium pyrrolidine dithiocarbamate and extracted into the fine droplets formed when mixing carbon tetrachloride (extraction solvent), methanol (disperser solvent) and the sample solution. After extraction, the phases are separated by centrifugation, and As(III) and Sb(III) are determined in the organic phase. As(V) and Sb(V) remain in the aqueous layer. Total inorganic As and Sb are determined after the reduction of the pentavalent forms with sodium thiosulphate. As(V) and Sb(V) are calculated by difference. The detection limits are 0.01 and 0.05 µg L^− 1 for As(III) and Sb(III), respectively, with an enrichment factor of 115. The relative standard deviation is in the 2.9–4.5% range. The procedure has been applied to the speciation of inorganic As and Sb in bottled, tap and sea water samples with satisfactory results.