Sb(III) and Sb(V) separation and analytical speciation by a continuous tandem on-line separation device in connection with inductively coupled plasma atomic emission spectrometry

A sensitive, precise and automated non-chromatographic method for Sb(III) and Sb(V) analytical speciation based on a continuous tandem on-line separation device in connection with inductively coupled plasma-atomic emission (ICP-AES) detection is proposed. Two on-line successive separation steps are included into this method: a continuous liquid-liquid extraction of Sb(III) with ammonium pyrrolidine dithiocarbamate (APDC) into methylisobuthylketone (MIBK), followed by direct stibine generation from the organic phase. Both separation steps are carried out in a continuous mode and on-line with the ICP-AES detector. Optimization of experimental conditions for the tandem separation and ICP-AES detection are investigated in detail. Detection limits for Sb(III) were 3 ng.mL(-1) and for Sb(V) 8 ng.mL(-1). Precisions observed are in the range +/- 5%. The proposed methodology has been applied to Sb(III) and Sb(V) speciation in sea-water samples.     

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.     

Hollow fiber supported liquid membrane extraction coupled with thermospray flame furnace atomic absorption spectrometry for the speciation of Sb(III) and Sb(V) in environmental and biological samples

A new method of hollow fiber supported liquid membrane extraction (HF-SLME) coupled with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for the speciation of Sb(III) and Sb(V) in environmental and biological samples has been developed. The method is based on the complex of Sb(III) with sodium diethyldithiocarbamate (DDTC). The formed hydrophobic complex is subsequently extracted into the lumen of hollow fiber, whereas Sb(V) is remained in aqueous solutions. The extraction organic phase was injected into TS-FF-AAS for the determination of Sb(III). Total Sb concentration was determined after reduction of Sb(V) to Sb(III) in the presence of l-cysteine and the extraction procedure mentioned above. Sb(V) was calculated by subtracting of Sb(III) from the total Sb. DDTC was used as complexing reagent. 1-Octanol was immobilized in the pores of the polypropylene hollow fiber as liquid membrane and also used as the acceptor solution. Some parameters that influenced extraction and determination were evaluated in detail, such as concentration of sodium diethyldithiocarbamate (DDTC), type of organic solvent, pH of samples, stirring rates, extraction time, as well as interferences. Under optimized conditions, a detection limit of 0.8 ng mL⁻¹ and an enrichment factor of 160 were achieved. The relative standard deviation (RSD) was 6.2% for Sb(III) (50 ng mL⁻¹, n = 5). The proposed method was successfully applied to the speciation of Sb(III) and Sb(V) in environmental and biological samples with satisfactory results.     

Separation of trace elements,In(III), Sn(IV), Sb(V) and Te(IV) by adsorption on activated carbon and graphite

Adsorption behaviour of trace elements, In(III), Sn(IV), Sb(V) and Te(IV) on activated carbon and graphite powder was studied. Adsorption characteristics of the ions enabled the separation of In(III)–Sn(IV), Sn(IV)–Sb(V) and Sb(V)–Te(IV) pairs. Applications to practical separation, milking of^113mIn from¹¹³Sn, removal of tin impurity from¹¹⁹Sb, and milking of¹¹⁹Sb from^119mTe, are presented.     

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.     

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.     

Simultaneous determination of Sb(III) and Sb(V) by partial least squares regression

A method for simultaneous spectrophotometric determination of Sb(III) and Sb(V) using multivariate calibration method is proposed. This method is based on the development of the reaction between the analytes and pyrogallol red at pH 2.00. The selection of variables was studied. A series of synthetic solutions containing different concentrations of Sb(III) and Sb(V) were used to check the prediction ability of the partial least squares model. The calibration curves were linear over the range of 0.3-3.4 and 0.3-3.0 μg ml⁻¹ for Sb(III) and Sb(V), respectively. The detection limits were 0.177 and 0.200 μg ml⁻¹ for Sb(III) and Sb(V), respectively.     

Speciation of mercury by continuous flow liquid-liquid extraction and inductively coupled plasma atomic emission spectrometry detection

An accurate, precise, sensitive and automated non-chromatographic method for methylmercury speciation based on a selective continuous liquid-liquid extraction of methylmercury, into xylene, as bromide and cold mercury vapour generation directly from the organic phase and final ICP-AES mercury detection is proposed. Both separation steps, liquid-liquid and gas-liquid are accomplished in a continuous mode and on line with ICP-AES as detector. The detection limit attained for methylmercury was 4ng·ml^–1 (as mercury). The precision of the determination at a concentration level around 20 times the detection limit was +-5%. The proposed methodology has been applied successfully to the speciation of methylmercury and inorganic mercury in spiked sea water and spiked urine samples.     

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.     

On-line preconcentration and determination of cobalt by DPTH-gel chelating microcolumn and flow injection inductively coupled plasma atomic emission spectrometry

This paper reports the development of a new methodology for the determination of cobalt in biological samples by using a flow injection system with loaded DPTH-gel as solid phase to preconcentrate analytes. The procedure is based on the on-line preconcentration of cobalt on a microcolumn of 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel). The trapped cobalt is then eluted with 1% tartaric acid and 1% citric acid (7.1 mL) and determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The analytical figures of merit for the determination of cobalt are as follows: detection limit (3S), 8.5 ng mL^–1; precision (RSD), 5.8% for 100 ng mL^–1 of cobalt; enrichment factor, 13 (using 7.3 mL of sample); sampling frequency, 40 h^–1 using a 60-s preconcentration time. For a 120-s preconcentration time (14.6 mL of sample volume) a detection limit of 5.7 ng mL^–1, an RSD under 5% at 50 ng mL^–1, an enrichment factor of 25, and a sampling frequency of 24 h^–1 were reported. The precision and accuracy of the method were checked by analysis of biological certified reference materials.     

Speciation of Sb(III) and Sb(V) by pH-control using three inorganic acids (hydrochloric, phosphoric and sulphuric)

Summary A method is described for the speciation of Sb(III) and Sb(V) using HG-AAS. The efficiency of stibine generation using different pH, from Sb(III) and Sb(V) solutions, was tested. At high pH-values Sb(V) is not reduced to form stibine, Sb(III) being selectively determined. The three acids HCl, H₂SO₄ and H₃PO₄ at controlled pH were used to generate stibine, H₃PO₄ being the most satisfactory for antimony speciation. The interference of Sb(V) was studied for the case of Sb(III) determination with stibine generation in H₃PO₄ medium (pH 1.81). The speciation of Sb(III) and Sb(V) is possible up to a ratio of 1:9.     

On-line redox speciation analysis of antimony using l-proline immobilized on controlled pore glass and hydride generation inductively coupled plasma optical emission spectrometry for detection

l-proline was immobilized on controlled pore glass to study the ability of this material for the separation and preconcentration of Sb(III) and Sb(V). The substrate was packed in a minicolumn and incorporated in a flow injection system. The effluents of the on-line solid phase extraction (before and after elution) were directly coupled to the hydride generation inductively coupled plasma optical emission spectrometry system. The effect of pH, sample (and eluent) volume, flow rates of sample loading and elution on separation of Sb(III) e Sb(V) were evaluated. Our experiments demonstrated that Sb(V) was not retained and it was selectively determined during the loading step, while retained Sb(III) was determined after elution. The proposed system was also used for the selective preconcentration of Sb(III). In this case, a preconcentration factor of 11 and a limit of detection of 90 ng L⁻¹ for Sb(III) were achieved when 8 mL of sample were loaded into the column. The speciation analysis of inorganic Sb in river water and effluent samples was performed using the proposed method. The values obtained for total Sb (obtained by sum of Sb(III) and Sb(V)) were in good agreement with expected values. Recoveries of Sb(III) and Sb(V) in the river water Standard Reference Material 1640 (from National Institute of Standard and Technology) and spiked river waters were between 83 and 111%.     

Use of 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel for automated preconcentration and selective determination of antimony(III) by flow-injection electrothermal atomic absorption spectrometry

Selective sorption of Sb(III) on a microcolumn packed with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel) has been used for determination of Sb(III). A flow-injection system comprising a microcolumn connected to the tip of the autosampler was used for preconcentration. The sorbed antimony was eluted with nitric acid directly into the graphite furnace and determined by AAS. The detection limit for antimony under the optimum conditions was 0.3 ng mL^–1. This procedure was used for determination of antimony in natural water, soil, vegetation, and a certified sample of a city waste incineration ash (BCR 176).     

On-line determination of Sb(III) and total Sb using baker's yeast immobilized on polyurethane foam and hydride generation inductively coupled plasma optical emission spectrometry

The yeast Saccharomyces cerevisiae was immobilized in cubes of polyurethane foam and the ability of this immobilized material to separate Sb(III) and Sb(V) was investigated. A method based on sequential determination of total Sb (after on-line reduction of Sb(V) to Sb(III) with thiourea) and Sb(III) (after on-line solid–liquid phase extraction) by hydride generation inductively coupled plasma optical emission spectrometry is proposed. A flow system assembled with solenoid valves was used to manage all stages of the process. The effects of pH, sample loading and elution flow rates on solid–liquid phase extraction of Sb(III) were evaluated. Also, the parameters related to on-line pre-reduction (reaction coil and flow rates) were optimized. Detection limits of 0.8 and 0.15 μg L^− 1 were obtained for total Sb and Sb(III), respectively. The proposed method was applied to the analysis of river water and effluent samples. The results obtained for the determination of total Sb were in agreement with expected values, including the river water Standard Reference Material 1640 certified by the National Institute of Standards and Technology (NIST). Recoveries of Sb(III) and Sb(V) in spiked samples were between 81 ± 19 and 111 ±15% when 120 s of sample loading were used.     

Speciation analysis of inorganic arsenic in natural water by carbon nanofibers separation and inductively coupled plasma mass spectrometry determination

In this paper, carbon nanofibers (CNFs) as a novel solid phase extraction sorbent were developed for speciation preconcentration and separation of inorganic arsenic species As(III) and As(V) prior to determination by inductively coupled plasma mass spectrometry (ICP-MS). It was found that during all the steps of the separation, As(III) was selectively sorbed on the microcolumn packed with CNFs within a pH range of 1.0-3.0 in the presence of ammonium pyrroinedithiocarbamate (APDC), while As(V) was passed through the microcolumn without the retention. Various experimental parameters affecting the separation and determination of As(III) and As(V) have been investigated in detail. Under the optimized conditions, the detection limits of this method for As(III) were 0.0045 ng mL⁻¹ with an enrichment factor of 33 and 0.24 ng mL⁻¹ for As(V), and the relative standard deviations for As(III) and As(V) were 2.6% and 1.9% (n = 9, c = 1.0 ng mL⁻¹), respectively. In order to verify the accuracy of the method, a certified reference of water sample was analyzed, and the results obtained were in good agreement with the certified values. The proposed method was applied for the analysis of inorganic arsenic species in groundwater and lake water with the recovery of 92-106%.     

Determination of V(V), Nb(V) and Ta(V) as their 2-(5-nitro-2-pyridylazo)-5-diethylaminophenol complexes by reversed-phase high performance liquid chromatography

A method for the reversed-phase liquid chromatographic separation and determination of V(V), Nb(V) and Ta(V) as 2-(5-nitro-2-pyridylazo)-5 diethylaminophenol (5-NO₂-PADAP) complexes is reported. The metal complexes were eluted in 9 min with a mobile phase of methanol-water (54 : 46, v/v) containing 10 mmol L^–1 acetate buffer (pH 3.0) on an ODS column. The detection limits for V, Nb and Ta were 0.09, 0.13 and 1.41 ng mL^–1, respectively, with S/N=3. The analysis of a reference sample of a mineral is discussed. The results corresponded to the certified values, and recoveries of 98.3–101.4% have been obtained.     

Speciation of antimony by preconcentration of Sb(III) and Sb(V) in water samples onto nanometer-size titanium dioxide and selective determination by flow injection-hydride generation-atomic absorption spectrometry.

A novel method for prevention of the oxidation of Sb(III) during sample pretreatment, preconcentration of Sb(III) and Sb(V) with nanometer size titanium dioxide (rutile) and speciation analysis of antimony, has been developed. Antimony(III) could be selectively determined by flow injection-hydride generation-atomic absorption spectrometry, coexisting with Sb(V). Trace Sb(III) and Sb(V) were all adsorbed onto 50 m g TiO2 from 500 ml solution at pH 3.0 within 15 min, then eluted by 10 ml of 5 mol/l HCl solution. One eluent was directly used for the analysis of Sb(III); to the other eluent was added 0.5 g KI and 0.2 g thiourea to reduce Sb(V) to Sb(III), then the mixture was used for the determination of total antimony. The antimony(V) content is the mathematical difference of the two concentrations. Detection limits (based on 3sigma of the blank determinations, n=11) of 0.05 ng/ml for Sb(III) and 0.06 ng/ml for Sb(V), were obtained.     

Quantitative kinetic determination of Sb(V) and Sb(III) by spectrophotometric H-point standard addition method

The H-point standard addition method (HPSAM) was applied to kinetic data for simultaneous determination of Sb(V) and Sb(III) and also selectively determines Sb(V) in the presence of Sb(III). The method is based on the differences between rate of complexation of pyrogallol red with Sb(V) and Sb(III) at pH=2. Sb(V) can be determined in the range of 0.3-2.0 μg ml⁻¹ with satisfactory accuracy and precision in the presence of excess Sb(III). Good selectivity was obtained over the variety of metal ions. The proposed method was used for determination of Sb(V) and Sb(III) in river and spring water samples.     

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 arsenic, selenium and antimony species using HPLC/ICP-MS

A new method for the simultaneous separation and determination of four arsenic species [As(III), As(V), monomethylarsonic acid and dimethylarsinic acid], three selenium species [Se(IV), Se(VI) and selenomethionine] as well as Sb(III) and Sb(V) is presented. The speciation was achieved by on-line coupling of anion exchange high-performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS). Chromatographic parameters such as the composition and pH of the mobile phase were optimised. Limits of detection are below 4.5 μg L^–1 (as element) for Sb(III) and the selenium species and below 0.5 μg L^–1 for the other species. Precisions of retention times were better than 2% RSD and of peak areas better than 8% RSD for all the species investigated. Received: 13 January 1999 / Accepted: 4 March 1999