Determination of Mo and Bi in steels by electrothermal atomic absorption spectrometry after complexation and sorption on activated carbon

A simple method for the preconcentration of Mo and Bi in steels is proposed. The analytes are complexed with the ammonium salt of dithiophosphoric acid O,O-diethyl ester and sorbed onto activated carbon. After desorption into a small volume of nitric acid at low pH, Mo and Bi are determined by electrothermal atomic absorption spectrometry. Iron(III) is reduced to Fe(II), which is not complexed and not significantly retained on the carbon. Enrichment factor of 23 and 26 were obtained for Mo and Bi, respectively. The method was applied to the analysis of four certified reference steels, after acid dissolution in a microwave system and good agreement was obtained with the certified or recommended values.     

Determination of As and Sb in iron and steel by neutron activation analysis with multiple gamma-ray detection

Recycled steel products demands a new technique for determining tramp elements in steel. In this paper, As and Sb in iron certified reference materials were determined by neutron activation analysis with the multiple gamma-ray detection method. The determined values are in good agreement with certified and reference values. The lower determination limits (LDL) for As and Sb in high purity iron are 0.012 and 0.0025 ppm, respectively. As the demanded LDL for As and Sb is 0.1 ppm, the method described in this work is suitable for determining As and Sb in recycled steel.     

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.     

Determination of arsenic in scalp hair samples from exposed subjects using microwave-assisted digestion with and without enrichment based on cloud point extraction by electrothermal atomic absorption spectrometry

A simple and rapid cloud point extraction (CPE) procedure was applied for preconcentration of trace quantities of arsenic (As) in scalp hair samples. The samples were subjected to microwave-assisted digestion in a mixture of nitric acid and hydrogen peroxide (2 + 1, v/v) prior to preconcentration by CPE. The As in digested samples was complexed with ammonium pyrrolidine dithiocarbamate (APDC), and the resultant As-PDC complex was extracted by a nonionic surfactant, octylphenoxypolyethoxyethanol (Triton X-114). After centrifugation, the surfactant-rich phase was diluted with 0.1 M HNO3 in methanol and analyzed by electrothermal atomic absorption spectrometry. The experimental parameters, i.e., amount of APDC, concentration of Triton X-114, equilibrium temperature and time, were optimized. For validation of the proposed method, a certified reference material (CRM) of human hair (BCR 397) was used. No significant difference (P > 0.05) was observed between the experimental results and certified values of the CRM (paired t-test). The LOD and LOQ obtained under the optimal conditions were 0.025 and 0.083 microg/kg, respectively. The developed method was applied for the determination of As in scalp hair samples from male and female subjects of two villages of Khairpur Mir's, Pakistan.     

Determination of Te,Bi, Ni,Sb and Au by X-ray fluorescence spectrometry following electroenrichment on a copper cathode

The electrodepositons of Te, Bi, Ni, Sb and Au from aqueous solution of pH = 1 on the cathode surface have been studied for X-ray fluorescence analysis (XRF). A special holder for a copper electrode has been constructed to perform the electrodeposition process on only one side of the electrode. After electrolysis, the copper electrode can be easily removed from the holder; after rinsing it with water and drying it can be analyzed by XRF. The proposed method of sample preparation and preconcentration of Te, Bi, Ni, Sb, Au provides suitable samples which are devoid of the negative and undesirable effects of XRF analysis, such as particle size and matrix effects. The influence of time on the deposition yield has been examined. The method of preconcentration is efficient. The inhomogeneity of the prepared specimens has been studied using internal standard method. The calibration is based on using synthetic standards, certified reference materials and standard addition method. The best results are achieved by the standard addition method. The agreement between results obtained with XRF analysis and certified values is satisfactory and indicates the usefulness of the proposed method for determination of Te, Bi, Ni, Sb and Au in anode slime.     

Headspace single-drop microextraction with in situ stibine generation for the determination of antimony (III) and total antimony by electrothermal-atomic absorption spectrometry

A headspace-single drop microextraction method combined with electrothermal atomic absorption spectrometry (ETAAS) is developed for the extraction and preconcentration of antimony(III) and total antimony into a Pd(II)-containing aqueous drop after hydride generation. Experimental variables such as hydrochloric acid and sodium tetrahydroborate concentrations, sample volume, Pd(II) concentration in the acceptor phase and microextraction time were optimized. A 2^6-2 _IV factorial fractional design was initially used for screening the effect of the variables, followed by an univariate approach. The method showed a great freedom from interferences caused by hydride-forming elements and transition metals. The detection limit of Sb(III) was 25 pg mL^?1. A preconcentration factor of 176 is achieved in 3 min. The repeatability, expressed as relative standard deviation, was 4.7%. The method was validated against two certified reference materials (NWRI-TM 27.2 and NIST 2711) and applied to the determination of Sb(III) and total Sb in waters.     

Simultaneous determination of trace arsenic, antimony, bismuth and selenium in biological samples by hydride generation-four-channel atomic fluorescence spectrometry

A new and sample technique for the simultaneous determination of trace arsenic, antimony, bismuth and selenium in biologic samples by hydride generation-four-channel nondispersive atomic fluorescence spectrometry was development. The conditions of instrumentation and hydride generation of arsenic, antimony, bismuth and selenium were optimized. For reducing hexavalent Se to the tetravalent state was to heat the sample with 6 mol l⁻¹ HCl, and then pre-reducing pentavalent As and Sb to the trivalent state was achieved by the addition of 0.05 mol l⁻¹ thiourea. The interferences of coexisting ions were evaluated. Under optimal conditions, the detection limits for As, Sb, Bi and Se were determined to be 0.03, 0.04, 0.04 and 0.03 ng ml⁻¹, respectively. The precision for seven replicate determinations at the 5 ng ml⁻¹ of As, Sb, Bi and Se were 0.9, 1.2, 1.3 and 1.5% (R.S.D.), respectively. The proposed method was successfully applied to the simultaneous determination of As, Sb, Bi and Se in a series of Chinese certified biological reference materials using simple aqueous standard calibration technique, the results obtained are in good agreement with the certified values.     

An in-syringe La-coprecipitation Method for the Preconcentration of Oxo-anion Forming Elements in Seawater Prior to an ICP-MS Measurement

A lanthanum (La) coprecipitation method with low sample consumption was explored for the preconcentration of oxo-anion forming elements prior to a measurement by inductively coupled plasma mass spectrometry (ICP-MS). The preconcentration procedure was composed of two main steps: (1) the formation of a coprecipitate with the lowest possible La and (2) the redissolution of target analytes with minimal use of nitric acid, and the elimination of high concentration La from the analysis sample. Each step was performed in a 25 mL-volume syringe to reduce the sample consumption and to avoid contamination from the experimental environment. Various parameters, such as the concentration and volume of La added into the sample solution, the precipitation pH, the aging time, and the volume of HNO(3) were optimized to obtain good recoveries and high detection sensitivities for V, As, Sb, and W, which could be hardly recovered by solid-phase extraction using a chelating resin. The obtained method was evaluated through the analysis of seawater reference materials (CASS-4 and NASS-5). The recoveries exceeded 80%, and the observed values were in good agreement with the certified values.     

Ultratrace determination of tin by hydride generation in-atomizer trapping atomic absorption spectrometry

A quartz multiatomizer with its inlet arm modified to serve as a trap (trap-and-atomizer device) was employed to trap tin hydride and subsequently to volatilize collected analyte species with atomic absorption spectrometric detection. Generation, atomization and preconcentration conditions were optimized and analytical figures of merit of both on-line atomization as well as preconcentration modes were quantified. Preconcentration efficiency of 95 ± 5% was found. The detection limits reached were 0.029 and 0.14 ng mL⁻¹ Sn, respectively, for 120 s preconcentration period and on-line atomization mode without any preconcentration. The interference extent of other hydride forming elements (As, Se, Sb and Bi) on tin determination was found negligible in both modes of operation. The applicability of the developed preconcentration method was verified by Sn determination in a certified reference material as well as by analysis of real samples.     

Lower limit of determination values for trace elements in iron certified reference materials by neutron activation analysis with multiple gamma-ray detection

Recycling steel products demands a new technique for determining tramp elements in steel. Tramp elements, As and Sb, in some iron certified reference materials were determined by neutron activation analysis with multiple gamma-ray detection method and reported in MTAA11. In MTAA12, the authors reported the lower limit of determination values (LDL) and the dispersion of this method. The values of the LDLs for As and Sb in high purity iron were 0.002 and 0.0009 μg·g⁻¹. The dispersion is small enough to satisfy the demand from materials science.     

Application of ultrasonic-assisted cloud point extraction/flame atomic absorption spectrometry (UA-CPE/FAAS) for preconcentration and determination of low levels of antimony in some beverage samples

Due to be able to migrate or leach from food packaging materials into the foods and/or beverages, development of a new, sensitive and selective analytical methods for low levels of antimony as a food contaminant is of great importance in terms of food safety. In this context, an ultrasonic-assisted cloud point extraction method was developed for the preconcentration and determination of antimony as Sb(III) using 4-(2-thiazolylazo)resorcinol (TAR) and 2-(2-thiazolylazo)-p-cresol (TAC) as chelating agents and sodium dodecyl sulfate as signal enhancing agent at pH 6.0 and mediated by nonionic surfactant, t-octylphenoxypolyethoxyethanol by flame atomic absorption spectrometry. Using the optimized conditions, the calibration curves obtained from Sb(III) with TAR and TAC were linear in the concentration ranges of 0.5–180 and 1–180 μg L^?1 with detection limits of 0.13 and 0.28 μg L^?1, respectively. The precision (as relative standard deviations, RSDs) was lower than 3.9 % (25 and 100 μg L^?1, n: 6). The method accuracy was validated by the analysis of two standard reference materials. The results obtained were statistically in a good agreement with the certified values at 95 % confidence limit. The method has successfully been applied to the determination of Sb(III) and total Sb in selected beverages, milk and fruit-flavored milk products before and after pre-reduction of Sb(V) to Sb(III) with a mixture of KI/ascorbic acid in acidic media. The Sb(V) contents of samples were quantitatively calculated from analytical difference between total Sb and Sb(III) levels.     

Determination of Ga, Ge, As, Se and Sb in fly ash samples by ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry

Ultrasonic slurry sampling electrothermal vaporization inductively coupled plasma mass spectrometry (USS-ETV-ICP-MS) has been applied to determine Ga, Ge, As, Se and Sb in fly ash samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Pd and ascorbic acid were used as the mixed modifiers to enhance the ion signals. This method has been applied to determine Ga, Ge, As, Se and Sb in NIST SRM 1633a and 1633b coal fly ash reference materials and a fly ash sample collected locally. Since the sensitivities of the elements studied in slurry solution and aqueous solution were different slightly, analyte addition technique was used for the determination of Ga, Ge, As, Se and Sb in these samples. The As and Se analysis results of the reference materials agreed with the certified values. The results for which no certified value was available were also found to be in good agreement between the ETV-ICP-MS results and the reference values. The reference value was obtained by digesting the samples and analyzing the digested sample solutions by pneumatic nebulization Dynamic Reaction Cell™ (DRC) ICP-MS. The method detection limits estimated from analyte addition curves were about 0.23, 0.13, 0.17, 0.25 and 0.11 μg g⁻¹ for Ga, Ge, As, Se and Sb, respectively, in original fly ash samples.     

Collection of trace metals with cationic surfactant-silica particles followed by flotation with an anionic surfactant for seawater analysis

The analysis of seawater for trace metals is important for pollution monitoring and better understanding of marine systems. The present paper describes an efficient preconcentration method for the determination of trace metals in seawater. Trace metals [Ni(II), Cu(II), Ga(III), Cd(II), Pb(II), and Bi(III)] in 1,000 mL of seawater sample were complexed with ammonium pyrrolidinedithiocarbamate and sorbed onto silica particles covered with cetyltrimethylammonium chloride. After the addition of sodium dodecyl sulfate, the particles were floated to the solution surface by bubbling and then collected by suction. The trace metals were desorbed with dilute nitric acid and determined by inductively coupled plasma–mass spectrometry. The rapid 200-fold preconcentration was demonstrated with certified seawater samples.     

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).     

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.     

In situ synthesis and preconcentration of cetylpyridinium complexed hexaiodo platinum nanoparticles from spent automobile catalytic converter leachate using cloud point extraction

In the present study, a green chemistry based cloud point extraction (CPE) method has been developed for the in situ synthesis and preconcentration of cetylpyridinium complexed hexaiodo platinum nanoparticles (Pt-I NP) from the leachate of spent automobile catalytic converter using potassium iodide (KI) and assisted by a combination of cationic and non-ionic surfactants; cetylpyridinium bromide (CPB) and Triton X-114, respectively. The process parameters such as concentrations of hydrochloric acid, platinum, KI, sodium chloride, CPB, Triton X-114; incubation temperature and complexation time on CPE were optimized. The synthesized nanoparticles were characterized by UV–visible spectroscopy (UV–vis), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and zeta potential techniques. The formation of Pt-I NP was followed with UV–vis. The XRD pattern established the tetragonal crystal structure of the produced nanoparticles. The nanoparticles were spherical in shape and the particle size obtained with TEM was about 5.6 nm. Further, the preconcentrated nanoparticles were quantified by continuum source electro-thermal atomic absorption spectrometry (ET-AAS) and a preconcentration factor of 25 was obtained for a reaction volume of 25 mL. The accuracy of the developed method was confirmed by analyzing the certified reference materials such as CCRMP PTM-1a (copper-nickel sulphide matte) and CCRMP PTC-1a (copper-nickel sulphide concentrate). The current CPE protocol demonstrates advantages such as simultaneous synthesis and preconcentration; synthesis at micromolar concentration from metal scrap, higher nanoparticle recovery; biodegradability and biocompatibility of the employed surfactants and dual solubility of the synthesized Pt-I NP. Thus, the developed method can be applied for the separation, large scale synthesis and preconcentration of Pt-I NP from various environmental and industrial wastes, in a single pot.     

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 and Determination of Trace Amount of Inorganic Arsenic in Water,Environmental and Biological Samples

A new speciation and preconcentration method based on dispersive liquid‐liquid microextraction has been developed for trace amounts of As(III) and As(V) in urine and water samples. At pH 4, As(III) is complexed with ammoniumpyrrolidine dithiocarbamate and extracted into 1‐Hexyl‐3‐methylimidazolium hexafluorophosphate, as an ionic liquid (IL) and As(III) is determined by electrothermal atomic absorption spectrometery (ETAAS). Arsenic(V) in the mixing solution containing As(III) and As(V) was reduced by using KI and ascorbic acid in HCl solution and then the procedure was applied to determination of total arsenic. Arsenic(V) was calculated as the difference between the total arsenic content and As(III) content. The effect of various parameters on the recovery of the arsenic ions has been studied. Under the optimum conditions, the enrichment factor 135 was obtained. The proposed method was successfully applied to the determination of trace amounts of As(III) and As(V) in water and biological samples.     

Zinc and iron determination in serum and urine samples of thyroid patients using cloud point extraction

A simple and rapid cloud point extraction method was applied for preconcentration of trace quantities of zinc (Zn) and iron (Fe) in biological samples (serum and urine) of thyroid patients prior to determination by flame atomic absorption spectrometry. The metals in serum and urine samples were complexed with 1-(2-thiazolylazo)-2-naphthol and entrapped in the surfactant octylphenoxypolyethoxyethanol (Triton X-114). After centrifugation, the surfactant-rich phase was diluted with 0.1 M HNO3 in methanol. For optimum recovery of analytes, the influences of the analytical parameters, including pH and amounts of complexing and surfactant reagents, were investigated. Enrichment factors of 66.4 and 70.2 were obtained for the preconcentration of Zn(II) and Fe(III), respectively. The obtained results showed sufficient recoveries (>98%) for Zn(II) and Fe(III) in certified reference materials (CRMs). The proposed method was applied to the determination of Zn(II) and Fe(III) in biological (serum and urine) samples and CRMs.     

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.