Electrothermal Atomic Absorption Spectrometric Determination Research Articles

Nanocomposite Magnetite-Kaolin for Rh Preconcentration and Determination by Electrothermal Atomic Absorption Spectrometry.

A preconcentration technique with a magnetite-kaolin adsorbent capable of magnetic separation was developed for the determination of rhodium in environmental samples. The magnetite-kaolin nanocomposite was prepared for the preconcentration of rhodium in an aqueous solution prior to an electrothermal atomic absorption spectrometric determination. The detection limit (3S/N) of rhodium was 16 pg mL-1 under the optimum conditions. Even though matrix elements existed in 103 fold excess in aqueous solution, the rhodium adsorption could be not affected by the matrix. The present method could be applied to the determination of Rh in an aqueous solution. The advantages are easy preparation of the adsorbent and fast magnetic separation.

Preconcentration of Pb with Aminosilanized Fe3O4 Nanopowders in Environmental Water Followed by Electrothermal Atomic Absorption Spectrometric Determination

A new preconcentration method to determine lead in environmental waters using the aminosilanized magnetite Fe3O4 powder sorbent has been developed. The preconcentration method was combined with electrothermal atomization atomic absorption spectrometry (ETAAS) and a graphite atomizer. Trace amount of sorbent (3 mg) could be applied into the preconcentration of Pb. According the preconcentration, the detection limits were 14 and 19 pg·mL−1 with bare and aminosilanized Fe3O4, respectively. The effect of interferent elements such as Al, Ca, Co, Fe, K, Mg, Na, Ni, and Zn (1000 ng·mL−1 versus Pb 1 ng·mL−1) on the preconcentration of Pb using bare magnetite was evaluated, and some elements (Al, Ni, and Zn) were found to interfere with the Pb preconcentration. The aminosilanized Fe3O4 sorbent was found to be effective in eliminating the severe interferences. The enrichment factors were 34 for the preconcentration with aminosilanized Fe3O4. The recovery of spiked Pb in the case of the sorbent with aminosilanized Fe3O4 was in the range of 75 to 110%. From the analytical data, the preconcentration technique was found to be useful for the determination of trace lead in environmental waters.

A newly synthesized graft copolymer for magnetic solid phase microextraction of total selenium and its electrothermal atomic absorption spectrometric determination in food and water samples

A newly synthesized polystyrene-g-polyoleic acid-g-polyethylene glycol graft copolymer (PoleS-PEG) was used as adsorbent in the solid phase microextraction of selenium ions by using electrothermal atomic absorption spectrometry (ETAAS). Neodymium magnet was used for separation of analyte ions. Various analytical parameters such as pH, adsorbent amount, mixing time, eluent solution, sample volume, etc. were optimized. The matrix effects of some cations and anions were also studied. The capacity of the adsorbent was found 11.5 mg g−1. The preconcentration factor was found to be 50. The detection limit (LOD) and quantification limit (LOQ) were found 6.06 ng L−1 and 20 ng L−1, respectively. The calibration curve was linear in the range of 0.02–4.0 μg L−1. Relative standard deviation was found 3.2%. The accuracy of the method was provided by using standard reference materials. The optimized method was successfully applied to natural water and food samples.

Comparison of the sorption capacities of 1,10-phenanthroline and 2,2-bipyridyl complexes with cadmium on activated carbon and graphene oxide

In this study adsorption potential of oxidation activated carbon (ox-AC) and graphene oxide (GO) was investigated. Cd(II) was bound to cationic complexes with 1,10-phenanthroline or 2,2-bipyridyl. The sorbents have been used for the dispersive solid-phase extraction of Cd(II) prior to its inductively coupled plasma optical emission spectrometric or electrothermal atomic absorption spectrometric determination. The influences of the various analytical parameters including pH, eluent type, ligand amount, sample volume and sorption time on the recovery efficiencies of Cd(II) were investigated. The limit of detection for activated carbon - 1,10-phenanthroline and activated carbon - 2,2-bipyridyl were 0.006 and 0.016 ng mL−1, respectively. For graphene oxide with 1,10-phenanthroline and graphene oxide with 2,2-bipyridyl obtained limit of detection were 0.046 and 0.091 ng mL−1, respectively. Maximum adsorption capacities and preconcentration factors were compared. The equilibrium sorption fitted better to the Langmuir isotherm. The method was validated with the certified reference materials ERM-BB186 and SRM 1640a.

Column preconcentration and electrothermal atomic absorption spectrometric determination of rhodium in some food and standard samples

In the present work, an electrothermal atomic absorption spectrometric method has been developed for the determination of ultra-trace amounts of rhodium after adsorption of its 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol/tetraphenylborate ion associated complex at the surface of alumina. Several factors affecting the extraction efficiency such as the pH, type of eluent, sample and eluent flow rates, sorption capacity of alumina and sample volume were investigated and optimized. The relative standard deviation for eight measurements of 0.1 ng/mL of rhodium was ±6.3%. In this method, the detection limit was 0.003 ng/mL in the original solution. The sorption capacity of alumina and the linear range for Rh(III) were evaluated as 0.8 mg/g and 0.015-0.45 ng/mL in the original solution, respectively. The proposed method was successfully applied for the extraction and determination of rhodium content in some food and standard samples with high recovery values.

Speciation of ultra-trace amounts of inorganic arsenic in water and rice samples by electrothermal atomic absorption spectrometry after solid-phase extraction with modified Fe3O4 nanoparticles

A new magnetic adsorbent, 3-mercaptopropionic acid coated 3-aminopropyl triethoxysilane modified Fe3O4 nanoparticle, was synthesised and used for the extraction and preconcentration of arsenic ions in aqueous solutions followed by electrothermal atomic absorption spectrometric determination. The adsorbent was characterised by TEM, SEM, XRD and FT-IR techniques and the method used the unique properties of magnetic nanoparticles, namely, high surface area and superparamagnetism which gave it the advantages of high extraction capacity, fast separation and low adsorbent consumption. Different parameters affecting extraction efficiency of the analyte including pH value, sample volume, adsorbent amount, extraction time and desorption conditions were investigated and optimised. Under the optimum conditions, wide linear range of 30–25,000 ng L−1 and low detection limit of 10 ng L−1 were obtained. The interday and intraday precisions (as RSD%) for five replicates determination of 50 and 25,000 ng L−1 of arsenic ions were in the range of 2.3–3.2%. Furthermore, no significant interference was observed in the presence of coexisting ions and high preconcentration factor of 198 was obtained. The adsorption isotherm followed Langmuir model and its kinetic was second-order. The accuracy of the method was validated by analysing certified reference materials for water and rice with satisfactory recoveries. Finally, the proposed method was successfully applied for the determination of ultra-trace amounts of arsenic in rice and water samples.

Determination of Nickel in Water, Food, and Biological Samples by Electrothermal Atomic Absorption Spectrometry After Preconcentration on Modified Carbon Nanotubes

A new and sensitive SPE method using modified carbon nanotubes for extraction and preconcentration, and electrothermal atomic absorption spectrometric determination of nickel (Ni) in real samples at ng/L levels was investigated. First, multiwalled carbon nanotubes were oxidized with concentrated HNO3, then modified with 2-(5-bormo-2-pyridylazo)-5-diethylaminophenol reagent. The adsorption was achieved quantitatively on a modified carbon nanotubes column in a pH range of 6.5 to 8.5; the adsorbed Ni(II) ions were then desorbed by passing 5.0 mL of 1 M HNO3. The effects of analytical parameters, including pH of the solution, eluent type and volume, sample volume, flow rate of the eluent, and matrix ions, were investigated for optimization of the presented procedure. The enrichment factor was 180, and the LOD for Ni was 4.9 ng/L. The method was applied to the determination of Ni in water, food, and biological samples, and reproducible results were obtained.

Electrothermal atomic absorption spectrometric determination of cadmium in environmental samples with niobium wire preconcentration method

A preconcentration method by adsorption of cadmium on a niobium wire was developed for the environmental waters, followed by electrothermal atomic absorption spectrometry with a tungsten tube atomizer. After the preconcentration, the niobium wire was directly inserted into the tungsten tube atomizer. In the preconcentration (adsorption) process of cadmium, the optimal immersing time was 60 s. The effects of large amounts of concomitants on the preconcentration of cadmium were evaluated. When 103–104 fold excess of matrix elements existed in aqueous solution at pH 4 and 9, the cadmium response was profoundly affected by the matrix elements. However, the cadmium absorption signal was not significantly influenced at pH 7. Therefore, pH 7 was selected for the application into the real environmental samples. Under the optimal conditions, the detection limit (3S/N) for cadmium by the niobium wire preconcentration method was 7.0 pg mL−1 and the relative standard deviation was 6.8%. The method with preconcentration on a niobium wire was applied to the determination of cadmium in water and proved to be sensitive, simple and convenient. Because this preconcentration method can be utilized in the in situ treatment of trace cadmium in environmental water samples, it was unnecessary to carry the water samples to the analytical work place. The technique was shown to be useful for the determination of cadmium in environmental water samples at 0.1–1 µg L−1 levels.

Evaluation of ion imprinted polymers for the solid phase extraction and electrothermal atomic absorption spectrometric determination of palladium in environmental samples

The complexes of Pd(II) with ammonium pyrrolidinedithiocarbamate (APDC), N,N′-diethylthiourea (DET) and dimethylglyoxime (DMG) were prepared and imprinted into a polymeric network. The ion-imprinted polymers (IIPs) were synthesized by copolymerization of 4-vinylpyridine (VP) and styrene as functional monomers and divinylbenzene as a cross-linking agent in the presence of 2,2-azo-bis-isobutyronitrile as an initiator. The influence of sample volume, pH and flow rate on the extraction efficiency of Pd was studied under dynamic conditions. Pd(II) could be quantitatively retained on each of the studied sorbents at the pH range of 0.5 to 1.0, and eluted with an acidic solution of thiourea. The polymer with the imprinted Pd-DET-VP complex offered the highest selectivity for Pd(II) over certain matrix components, such as Pt(IV), Ni(II) and Cu(II). The low sample pH is an important advantage of the separation procedure, as it allows an effective separation of Pd(II) from complex environmental matrices. The developed separation method was successfully applied to the electrothermal atomic absorption spectrometric (ETAAS) determination of trace amounts of Pd in tap and river water, grass, and certified platinum ore (CRM SARM 7 and SARM 76) samples with reproducibility below 6.5%. The detection limit for Pd(II) obtained by ETAAS after the pre-concentration on Pd-DET-VP polymer was 0.012 ng mL−1 for 75 mL sample volume.

A novel ion imprinted polymer as a highly selective sorbent for separation of ruthenium ions from environmental samples

A complex of Ru(III) with benzaldehyde thiosemicarbazone was used for the preparation of new ruthenium ion imprinted polymers. The polymers were synthesized using 4-vinylpyridine and styrene as functional monomers, divinylbenzene as a cross-linking agent, and ethanol or chloroform as a porogen in the presence of 2,2′-azobisisobutyronitrile as an initiator via the bulk polymerization technique. The polymers were used in dynamic mode as a selective sorbent for solid phase extraction of Ru(III) ions. The analyte was efficiently retained on the polymers at pH 8.0 ± 0.1 and eluted with 2 mL of 0.3 mol L−1 thiourea in 0.3 mol L−1 HCl. The influence of the type of porogen (ethanol and chloroform) and column size on the separation of analyte on the prepared material was also studied. The efficiency of retention and elution and sample flow rates were higher on columns of smaller diameter and the polymer prepared in ethanol. The analytical performance of the polymer prepared in ethanol such as the recovery of the Ru(III) ions, the reproducibility of the results (<3%), the limit of detection (0.26 ng mL−1), the selectivity in the presence of Pt(IV), Pd(II), Rh(III), Co(II) ions and the sorption capacity (237.4 μg g−1) was superior in comparison to other ruthenium imprinted polymers. The developed separation procedure was successfully applied to electrothermal atomic absorption spectrometric determination of trace amounts of ruthenium in tap and river water, municipal sewage, road runoff, and grass.

Solidified floating organic drop microextraction–electrothermal atomic absorption spectrometry for ultra trace determination of antimony species in tea, basil and water samples

Solidified floating organic drop microextraction was applied as a separation/preconcentration step prior to the electrothermal atomic absorption spectrometric (ETAAS) determination of ultra trace of antimony species. The method was based on the formation of an extractable complex between Sb(III) and ammonium pyrrolidinedithiocarbamate at pH ~ 5, while Sb(V) was remained in the aqueous phase. The antimony extracted into 1-undecanol was determined by ETAAS. Total antimony was determined after the reduction of Sb(V) to Sb(III) with potassium iodide and ascorbic acid. The amount of Sb(V) was determined from the difference of concentration of total antimony and Sb(III). Under the optimum conditions an enhancement factor of 437.5 and a detection limit of 5.0 ng L−1for the preconcentration of 25 mL of sample was achieved. The relative standard deviation at 300 ng L−1 of antimony was found to be 3.5 % (n = 6). The proposed method was successfully applied to the determination of antimony in tea, basil and natural water samples.

Direct solid sampling electrothermal atomic absorption spectrometric determination of toxic and potentially toxic elements in certified reference materials of brown coal fly ash

This work describes a method for the direct determination of Bi, Cd, Cr, Ni, Pb, Sb, Sn and Zn in reference materials of brown coal fly ash, using solid sampling electrothermal atomic absorption spectrometry. The use of chemical modifiers was found to be necessary for obtaining reproducible and sufficiently sensitive signals for the analytes under study. The mixture of Pd and Mg(NO3)2 was used for the determination of Bi, Cd, Pb, Sb, Sn and Zn, W (permanent modifier) in combination with Mg(NO3)2 (as aqueous modifier) provided well-defined signal profiles for Cr and Ni determination in coal fly ash samples. A systematic study focused on the use of alternative (less sensitive) lines for obtaining sufficient sensitivity. The following analytical lines were used: Bi 306.8nm, Cd 326.1nm, Cr 520.6nm, Ni 305.1nm, Pb 205.3nm, Sb 206.8nm, Sn 300.9nm, Zn 307.6nm. The limits of detection were 0.057μg g−1 for Bi, 0.21μg g−1 for Cd, 1.1μg g−1 for Cr, 1.4μg g−1 for Ni, 4.0μg g−1 for Pb, 0.13μg g−1 for Sb, 0.33μg g−1 for Sn and 16μg g−1 for Zn, respectively.

Separation of ruthenium from environmental samples on polymeric sorbent based on imprinted Ru(III)-allyl acetoacetate complex

A new ion imprinted polymer (IIP) for ruthenium recognition/pre-concentration was prepared via bulk polymerization using methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the cross-linking agent in the presence of Ru(III)–allyl acetoacetate complex as a template. The synthesized IIP was used as a new support for solid phase extraction (SPE) of ruthenium from environmental samples before electrothermal atomic absorption spectrometric determination. Variables affecting the SPE process, such as pH, load and elution flow rates, as well as concentration and volume of the eluting solution, were evaluated. The optimized procedure consists of a sample loading (sample pH of 6.5±0.5) through IIP-SPE columns containing 200mg of the synthesized IIP at a flow rate of 1.0mLmin−1. Elution was performed by passing 0.3molL−1 thiourea in 0.1molL−1 HCl at a flow rate of 1.0mLmin−1. For 10mL of sample pre-concentration factor of 20 was achieved. The limit of detection of the method was 0.32ngmL−1, while the relative standard deviation for six replicated separation processes was 2.5%. Good selectivity of the synthesized material for Ru(III) ions against other transition metal ions assures efficient removal of matrix of analyzed samples (tap and river water, municipal and road sewages, and grass) by the proposed IIP-SPE procedure.

An automated solid phase extraction coupled with electrothermal atomic absorption spectrometric determination of Pb(II) in high salt content samples

A novel Pb(II) analysis in dialysis concentrates and seawater samples has been developed with on-line separation and preconcentration system coupled with electrothermal atomic absorption spectrometer (FI-ETAAS). Lewatit Monoplus TP207 imminodiacetat chelating resin was used for separation and preconcentration of Pb(II) ions at pH 4.0. The influence of the analytical parameters such as type of eluent, flow rate of eluent and sample, eluent volume and matrix ions were investigated. W–Rh coated furnace was used as the atomization site. A preconcentration factor of 14 and a detection limit (3s/b) of 12ngL−1, along with the sampling frequency of 21h−1 were achieved with a 170s sample loading time and with 2.8mL sample consumption. The relative standard deviation (RSD) was 1.6% for 1μgL−1 Pb(II) level. The developed method was used for Pb(II) analysis in dialysis concentrates and seawater samples. The certified reference material (CRM403) experimental results are in good agreement with the certified value.

Selective solid phase extraction of platinum on an ion imprinted polymers for its electrothermal atomic absorption spectrometric determination in environmental samples

An ion-imprinted polymer (IIP) was obtained by copolymerization of methacrylic acid (as a functional monomer) and ethylene glycol dimethacrylate (as a crosslinking agent) in the presence of various chelators for Pt(II) ion and using 2,2′-azo-bis-isobutyronitrile as the initiator. Specifically, acetaldehyde thiosemicarbazone (AcTSn) and benzaldehyde thiosemicarbazone (BnTSn) were used as chelators. The IIPs were applied as sorbents for solid-phase extraction of Pt(II) and Pt(IV) ions from aqueous solutions. The effects of acidity and flow rate of the sample, of elution conditions and of potentially interfering ions were investigated. The imprinting effect of analyte is clearly demonstrated by the fact that only the IIP is capable of quantitative retention of Pt(II) and Pt(IV) ions. The method works best in the pH range from 0.5 to 1 and from 3.5 to 9.5. The ions can be recovered with an acidic solution of thiourea. The Pt-AcTSn polymer displays better sorption properties for the separation of analytes. The selectivity coefficients of the Pt-AcTSn and control polymers for Pt(IV) in the presence Pd(II), Rh(III), Ru(III), Al(III) and Cu(II) were calculated, and the sorbent capacity for Pt(IV) was found to be 4.56 μg g -1. The method was successfully applied to the determination of Pt(IV) by electrothermal atomic absorption spectrometry in tap water, tunnel dust and anode slime samples.

Slurry sampling electrothermal atomic absorption spectrometric determination of chromium after separation/enrichment by mercaptoundecanoic acid modified gold coated TiO2 nanoparticles

In this study, a novel preconcentration/separation technique based on the slurry analysis of chromium loaded on mercaptoundecanoic acid modified TiO2 core-Au shell nanoparticles prior to its determination by electrothermal atomic absorption spectrometry was described. For this purpose, at first, TiO2 nanoparticles were coated with gold shell and then modified with mercaptoundecanoic acid (MUA). Cr (III) was collected on the prepared sorbent by conventional batch technique. After separation of liquid phase, slurry of the sorbent was prepared and directly introduced into graphite furnace of atomic absorption spectrometry. By this way, all drawbacks due to elution procedure were eliminated. Optimum conditions for quantitative sorption and preparation of the slurry were investigated. The chromium in certificated sea-water and spiked drinking water was recovered in the range of 95% confidence level. The proposed technique was fast and simple as well as the risks of contamination and loss during elution were low. The limit of detection (3σ, N=10) was 0.34μgL−1.

Pyridine-functionalized mesoporous silica as an adsorbent material for the determination of nickel and lead in vegetables grown in close proximity by electrothermal atomic adsorption spectroscopy

A new, sensitive, and low cost solid-phase extraction method using pyridine-functionalized MCM-48 mesoporous silica for the extraction, pre-concentration, and electrothermal atomic absorption spectrometric determination of nickel and lead in food samples at ngmL−1 levels is described herein. The levels of nickel and lead in different types of vegetables grow in Shiraz–Iran and Rafsanjan–Iran were determined by electrothermal atomic absorption spectrometry. The use of two standard reference materials and also comparing the results to a standard reference procedure ensured the accuracy of this method. Factors, such as flow rate of extraction, and the type, pH, concentration, and volume of eluent, were appraised. The effect of various ions on recovery was also investigated. Detection limits of 0.11 and 0.14ngmL−1 were obtained for lead and nickel, respectively.

Microwave-Assisted Acid Extraction of Selenium from Medicinal Plants Followed by Electrothermal Atomic Absorption Spectrometric Determination

A simple and rapid microwave-assisted extraction (MAE) of selenium (Se) from medicinal plants was investigated using different concentrations of nitric acid and hydrochloric acid, sample mass, heating time, microwave energy, and plant particle size. The optimization strategy was carried out using multivariate methodologies. Electrothermal atomic absorption spectrometry was used to determine Se. The accuracy of the optimized procedure was evaluated by using certified reference materials with certified values for Se and a microwave-assisted acid digestion (MD) method for comparative purpose. No significant difference was observed (P > 0.05) when comparing the values obtained by the proposed MAE and MD methods (paired t-test). Under the optimum operating conditions, the LOD obtained from the standard calibration curve was 0.012 microg/L for Se. The average RSD of the MAE method varied between 4.05 and 7.53% (n = 6). The proposed method was successfully applied for the determination of Se in medicinal plants used as remedies for cancerous and infection diseases.

Tetradecyl(trihexyl)phosphonium chloride ionic liquid single-drop microextraction for electrothermal atomic absorption spectrometric determination of lead in water samples

A highly efficient single-drop microextraction (SDME) procedure using a low-cost room temperature ionic liquid (RTIL), i.e., tetradecyl(trihexyl)phosphonium chloride (CYPHOS IL 101), for Pb determination at trace levels in real water samples was developed. Lead was chelated with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) reagent and extracted into a 4 microL microdrop of CYPHOS IL 101. The RTIL drop was directly injected into the graphite furnace of the electrothermal atomic absorption spectrometer (ETAAS). Under optimal microextraction conditions, a preconcentration factor of 32 was achieved with only 1.5 mL of sample resulting in a phase-volume ratio of 375. The limit of detection (LOD) obtained was 3.2 ng L(-1) and the relative standard deviation (RSD) for 10 replicates at 0.5 microg L(-1) Pb(2+) concentration level was 4.9%, calculated at peak heights. The calibration graph was linear from concentration levels near the detection limits up to at least 4.5 microg L(-1) with a correlation coefficient of 0.9996. The accuracy of the methodology was evaluated by analysis of a certified reference material (CRM). The method was successfully applied to the determination of Pb in tap, mineral, well and river water samples.

Electrothermal atomic absorption spectrometric determination of cadmium and lead in traces in aquatic systems following flotation by two chromium(III) collectors

A fast flotation method for determination of cadmium and lead in aquatic systems by two chromium(III) collectors is described. The first collector is a colloid precipitate of hydrated chromium(III) oxide, Cr2O3· xH2O, while the second is a bulk chromium(III) pentamethylenedithiocarbamate, Cr(PMDTC)3. Cadmium and lead present in water are incorporated into the collector mass at pH 7.5 by addition of 20 mg of Cr(III) and 0.4 mmol of pentamethyleneammonium pentamethylenedithiocarbamate, PMA-PMDTC, to 0.5 L water sample. A solid precipitate was separated from the processed water system by air bubbles. After dissolving with strong acid, the solution is tested by electrothermal atomic absorption spectrometry (ETAAS). The limit of detection for Cd by flotation/ETAAS method is 0.002 μg L− 1, while for Pb is 0.04 μg L− 1. The precision of the method is expressed as relative standard deviations ranging of 5.0% for Cd (concentration range from 0.1 to 0.5 μg L− 1) and 4.25% for Pb (concentration range from 0.5 to 5 μg L− 1). The characteristic mass (mass that gives an integrated absorbance of 0.0044 s) of 1.06 pg for Cd and 16.7 pg for Pb were obtained. The method was validated by the standard additions and by its application to the reference materials (Surface water-SPS-SW-1, River Thames Water-LGC-6019).