Dispersive Liquid-Liquid Microextraction of Bismuth in Various Samples and Determination by Flame Atomic Absorption Spectrometry.

A dispersive liquid-liquid microextraction method for the determination of bismuth in various samples by flame atomic absorption spectrometry is described. In this method, crystal violet was used as counter positive ion for BiCl4 (-) complex ion, chloroform as extraction solvent, and ethanol as disperser solvent. The analytical parameters that may affect the extraction efficiency like acidity of sample, type and amount of extraction and disperser solvents, amount of ligand, and extraction time were studied in detail. The effect of interfering ions on the analyte recovery was also investigated. The calibration graph was linear in the range of 0.040-1.00 mg L(-1) with detection limit of 4.0 µg L(-1) (n = 13). The precision as relative standard deviation was 3% (n = 11, 0.20 mg L(-1)) and the enrichment factor was 74. The developed method was applied successfully for the determination of bismuth in various water, pharmaceutical, and cosmetic samples and the certified reference material (TMDA-64 lake water).

A new chelating reagent and application for coprecipitation of some metals in food samples by FAAS.

A new, simple and rapid coprecipitation method has been developed to separate and preconcentrate traces of Co(II), Cu(II), Fe(III), Pb(II) and Mn(II) in different samples prior to their determinations by flame atomic absorption spectrometry (FAAS). 2-[(E)-(8-hydroxy-2-methylquinolin-5-yl) diazenyl] benzoic acid (QAN) was firstly synthesized and characterized as a new chelating reagent for determination of some metals. IR spectra, (1)H-NMR spectrum and elemental analysis were evaluated for the characterization of the reagent. These metals were quantitatively recovered with Ni(II)/QAN precipitate in pH range of 8-10. Different factors such as sample volume, amount of QAN, and Ni(II) as carrier element, sample volume, and matrix effects for improving the quality of the preconcentration procedure were optimized. Under optimized experimentally established conditions, analytical detection limits were in the range of 0.03-0.83µgL(-1), while precision (RSD) was <3.5%, and enrichment factor was obtained as 100. The accuracy of the presented coprecipitation method was verified by the analysis of certified reference materials. The method was applied to the determination of the analytes in real samples such as food samples and make up products, and accuracy was found high (recoveries >95%).

Determination of some metal ions in various meat and baby food samples by atomic spectrometry.

In this paper, we report a simple and rapid solid phase extraction system for the separation/preconcentration and determination of Cd(II), Co(II), Cu(II), Fe(III), Cr(III), Pb(II), and Zn(II) ions by flame atomic absorption spectrometry (FAAS). This method is based upon the retention of metal ions on a column packed with poly[N-(3-methyl-1H-indole-1-yl)]-2-methacrylamide-co-2-acrylamido-2-methyl-1-propane sulphonic acid-co divinylbenzene] (MMAD) resin as a solid-phase extraction (SPE) sorbent at pH 8. At the optimized conditions, the limits of detection (3 s/b) between 0.12 and 1.6 µg L(-1), preconcentration factor of 100, and the relative standard deviation of ⩽1.8% were achieved (n=10). The accuracy of the method was verified by analyzing certified reference materials (CRMs) and performing recovery experiments. The developed method was successfully applied to the various natural water, meat products and baby food samples. The recoveries of analyte ions were found in added real samples and CRMs from 95% to 102%.

Global behaviour of a predator-prey like model with piecewise constant arguments.

The present study deals with the analysis of a predator-prey like model consisting of system of differential equations with piecewise constant arguments. A solution of the system with piecewise constant arguments leads to a system of difference equations which is examined to study boundedness, local and global asymptotic behaviour of the positive solutions. Using Schur-Cohn criterion and a Lyapunov function, we derive sufficient conditions under which the positive equilibrium point is local and global asymptotically stable. Moreover, we show numerically that periodic solutions arise as a consequence of Neimark-Sacker bifurcation of a limit cycle.

A solid phase extraction procedure for the determination of Cd(II) and Pb(II) ions in food and water samples by flame atomic absorption spectrometry.

A relatively rapid, accurate and precise solid phase extraction method is presented for the determination of cadmium(II) and lead(II) in various food and water samples. Quantitation is carried out by flame atomic absorption spectrometry (FAAS). The method is based on the retention of the trace metal ions on Dowex Marathon C, a strong acid cation exchange resin. Some important parameters affecting the analytical performance of the method such as pH, flow rate and volume of the sample solution; type, concentration, volume, flow rate of the eluent; and matrix effects on the retention of the metal ions were investigated. Common coexisting ions did not interfere on the separation and determination of the analytes. The detection limits (3 σb) for Cd(II) and Pb(II) were found as 0.13 and 0.18 µg L(-1), respectively, while the limit of quantification values (10 σb) were computed as 0.43 and 0.60 µg L(-1) for the same sequence of the analytes. The precision (as relative standard deviation was lower than 4% at 5 µg L(-1) Cd(II) and 10 µg L(-1) Pb(II) levels, and the preconcentration factor was found to be 250. The accuracy of the proposed procedure was verified by analysing the certified reference materials, SPS-WW2 Batch 108 wastewater level 2 and INCT-TL-1 tea leaves, with the satisfactory results. In addition, for the accuracy of the method the recovery studies (⩾ 95%) were carried out. The method was applied to the determination of the analytes in the various natural waters (lake water, tap water, waste water with boric acid, waste water with H2SO4) and food samples (pomegranate flower, organic pear, radish leaf, lamb meat, etc.), and good results were obtained. While the food samples almost do not contain cadmium, they have included lead at low levels of 0.13-1.12 µg g(-1).

On-line solid-phase separation/preconcentration for the determination of copper in urine by flame atomic absorption spectrometry.

A new on-line separation/preconcentration system was developed for the determination of Cu(II) ions by flame atomic absorption spectrometry in urine samples. A newly synthesized chelating resin, by anchoring eriochrome blue black R reagent to Amberlite XAD-16 resin, was used as a packing material for the selective separation/preconcentration of Cu(II) ions. The influence of the parameters on the determination of Cu(II) ions such as pH of sample solution, amount of the resin, eluent type, interfering ions and flow variables was studied. The detection limit of the method was 1.0 µg L(-1) while precision was 2.3% (n=15) at 50 µg L(-1) Cu(II) level. The adsorption capacity of the resin was 217 µg g(-1) Cu(II). The accuracy of the method was proven using TMDA-64 standard lake water and synthetic urine sample. The developed method has been applied successfully to the determination of copper in urine with satisfactory results.

Comparison of bone tissue trace-element concentrations and mineral density in osteoporotic femoral neck fractures and osteoarthritis.

PURPOSE: This study examined the role of trace elements in osteoporosis by comparing the trace-element concentrations in bone and the radiographic bone density and bone mineral density (BMD) of patients with osteoporotic femur fractures and osteoarthritis. PATIENTS AND METHODS: The study enrolled 30 patients operated on for proximal femoral fractures after falls, and another 30 patients undergoing hip arthroplasty at the same center for hip osteoarthritis. Bone samples were obtained during the surgical procedures. The density of the bone samples was assessed using computed tomography and the Hounsfield scale. The levels of Ca(II), Mg(II), and other trace elements in the bone samples were determined using flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry. In addition, BMD, Z-scores, and T-scores were measured in the unaffected hips of all patients using dual-energy X-ray absorptiometry. RESULTS: Magnesium (1,908 ± 507 versus 2,540 ± 435, P<0.05), calcium (10.4 ± 3.5 versus 13.9 ± 3.7, P<0.05), and zinc (2,342 ± 1,252 versus 3,145 ± 1,604, P<0.05) µg g(-1), levels were significantly lower in the bone samples in the fracture group. The groups did not differ in the other biochemical parameters. All dual-energy X-ray absorptiometry findings were significantly worse in the fracture group than in the osteoarthritis group. However, the groups did not differ in femoral neck density assessed radiologically using the Hounsfield scale. The following parameters were negatively correlated with age: magnesium, r=-0.436, P<0.001; calcium, r=-0.331, P=0.01; T-score, r=-0.381, P=0.003; Z-score, r=-0.267, P=0.043; and BMD, r=-0.365, P=0.004. CONCLUSION: Ca(II), Mg(II), and Zn(II) appear to play important roles in bone breakdown/synthesis. Further studies of the roles of trace elements in the etiology and treatment of osteoporosis are warranted. We found decreased bone levels of Ca, Mg, and Zn in patients with osteoporotic fractures compared to subjects with osteoarthritis.

Resting eggs as new biosorbent for preconcentration of trace elements in various samples prior to their determination by FAAS.

In this study, the resting eggs of aquatic creatures living in freshwater (Daphnia, Cladocera, Crustacean) ecosystems were used as a novel biosorbent extractant for synchronous preconcentration of trace Cd(II), Co(II), Cu(II), Mn(II), and Ni(II) previous to measurement by flame atomic absorpiton spectrometry (FAAS). Using column procedures, optimization studies were conducted to realize the effective adsorption of the analyte ions such as the solution pH, amount of the biosorbent, volume of the sample, interfering ions, etc. A high preconcentration factor of 67 and low relative standard deflection of ≤4.1% (n=8) were obtained. The invention constrains based on the 3 s/b criterion were 2.4 for Cd(II), 41.4 for Co(II), 4.2 for Cu(II), 3.0 for Mn(II), and 9.6 µg L(-1) for Ni(II). The accuracy of the method was verified by analysis of a certified standard reference material. The used procedure was applied to the definition of the analytes in diverse environmental samples with convincing results. Consequently, the resting eggs of Daphnia can be used as a biosorbent for preconcentration and biosorption studies.

Development of a new on-line system for the sequential speciation and determination of chromium species in various samples using a combination of chelating and ion exchange resins.

A new on-line flow injection (FI) procedure for the sequential separation, preconcentration and speciation of Cr(III)/Cr(VI) species in different matrices is described based on the combining of solid phase extraction and flame atomic absorption spectrometry (FAAS). Poly 2-(5-methylisoxazol)methacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid-co-divinyl-benzene and Dowex 21K resins were used as chelating and ion-exchange materials for the separation/preconcentration of Cr(III) and Cr(VI) ions, respectively. Trace amounts of chromium retained on the resins were eluted sequentially with HNO3 and then introduced directly to the nebulizer-burner system of FAAS. The optimum conditions such as pH of the sample solution, amount of the resin, volume of the sample and interfering ions, which are effective on the quantitative recovery of the analytes, were investigated for sequential determination of Cr(III) and Cr(VI) ions. The preconcentration factors were found to be 48 and 30 for Cr(III) and Cr(VI), and the detection limits corresponding to three times the standard deviation of the blank (3s/b) were 0.05 and 0.3 µg L(-1), respectively. The method was verified by analyzing a certified reference material. The proposed method was applied to the determination based on the speciation of chromium in various real samples with satisfactory results.

Chromium speciation in environmental samples by solid- phase extraction using lewatit ionac SR-7 resin and flame atomic absorption spectrometry.

A new method for the speciation, preconcentration, and separation of Cr(lll) and Cr(VI) species in different matrixes was developed using SPE combined with flame atomic absorption spectrometry. Theprocedure is based on the exchange of Cr(VI) ions as CrO(4)(2-) with CI- ions on Lewatit lonac SR-7 ion-exchange resin. After the oxidation of Cr(lll) to CrO(4)(2-) ions by concentrated H202 in basic medium, the procedure was applied to the determination of total Cr. Cr(lll) was calculated as the difference between the total Cr and Cr(VI) contents. The influence of the analytical parameters including the pH of the solution, amount of resin, eluent type, sample volume, and flow rates of the sample and eluent solutions were investigated. No considerable interferences were observed from: other anions and cations investigated in the Cr speciation. The preconcentration factor was found to be 500. The LOD for Cr(VI), corresponding to three times the SD of the blank, was 0.003 µg/L. The sorption capacity and binding equilibrium constant were calculated as 17.2 mg/g and 2.54 L/mg, respectively. The accuracy of the method was verified by analyzing certified reference materials. The proposed method was applied to the speciation of Cr species in real samples with satisfactory results.

Synthesis, characterization and application of a novel ion-imprinted polymer for selective solid phase extraction of copper(II) ions from high salt matrices prior to its determination by FAAS.

A new Cu(II)-imprinted sorbent has been prepared by using 5-methyl-2-thiozylmethacrylamide (MTMAAm). The monomer of Cu(II)-MTMAAm complex was synthesized and copolymerized in the presence of ethyleneglycol dimethacrylate cross-linker via bulk polymerization method. The resulting Cu(II)-imprinted polymer was characterized by FT-IR spectroscopy and scanning electron microscopy (SEM). Copper ions were removed from the polymer with 1.0 mol L(-1) HNO3 and determined by flame atomic absorption spectrometry (FAAS). The imprinted polymer showed higher selectivity for Cu(II) in comparison to the non-imprinted polymer. Relative selectivity coefficients (k') for Cu(II)/Zn(II), Cu(II)/Ni(II) and Cu(II)/Co(II) were 9.1, 14.8 and 26.6, respectively. The imprinted polymer was examined as a column packing material for solid phase extraction of Cu(II) from various matrices. The effects of solution pH, acid eluents and interfering ions were investigated. The poylmer possesses selective extraction of Cu(II) within pH range from 5.0 to 6.5. The relative standard deviation and limit of detection (3s) of the method were evaluated as 1.4% and 0.9 µg L(-1), respectively. The accuracy of the method was verified by analysis of two certified reference materials (CWW-TM-D and SRM 3280) and then applied to the determination of Cu in seawater, lake water and tap water samples, and hemodialysis concentrates and multivitamin/multielement supplements.

Determination of palladium by on-line flow-injection direct spectrophotometry in environmental samples using 2,2'-furyldioxime as a chelator.

A new, sensitive, and accurate on-line spectrophotometric method for the determination of palladium was developed. The method is based on the reaction between Pd(II) and 2,2'-furyldioxime in nitric acid medium. The absorbance of the complex is spectrophotometrically measured at 410 nm with a diode-array detector. Several factors that influence the analytical performance of the method such as acidity, flow rates of the reagent and sample solutions, concentration of the reagent, and effect of interfering ions were investigated. The calibration curve was obtained in the range of 0.01-10.0 mg L(-1) Pd(II). The detection limit was 0.1 µg L(-1) while the relative standard deviation of the method was found to be 1.2% (n=13) at 4.0 mg L(-1) Pd(II) level. The sample throughput was 275 h(-1). The method was successfully applied to the determination of palladium in catalytic converter, anodic slime, road sediment, ore, and water samples.

Synthesis, characterization and application of a new chelating resin for on-line separation, preconcentration and determination of Ag(I) by flame atomic absorption spectrometry.

A simple and reliable on-line separation/preconcentration procedure was developed for the determination of trace levels of Ag(I) by flame atomic absorption spectrometry. Poly[N-(3-methyl-1H-indol-1-yl)-2-methacrylamide-co-2-acrylamido-2-methyl-1-propane sulfonic acid-co-divinylbenzene] was synthesized and characterized as a new chelating resin for the first time. Ag(I) was sorbed on the chelating resin, from which it could be eluted with 3 mol L(-1) HCl and then introduced directly to the nebulizer-burner system for flame atomic absorption spectrometry. The parameters influential on the determination of Ag(I) ions such as the pH of the sample solution, amount of resin, eluent type, interfering ions and flow variables were studied. Under the optimum conditions, the calibration graph obtained was linear over the concentration range of 2-20 µg L(-1). The detection limit of the method (3σ) was 0.3 µg L(-1) while precision was 1.5% (n=25) at the level of 10 µg L(-1) Ag(I). The limit of quantification for the method, based on 20 σ, was 2.0 µg L(-1). The enrichment factor was found to be 65 while the optimized sample volume was 13.6 mL. The accuracy of the method was performed by analyzing certified reference materials. The developed method was applied successfully for the determination of silver in different water samples with satisfactory results.

Determination of some trace metals by FAAS after solid-phase extraction with amberlite XAD-1180/TAN chelating resin.

A new chelating resin was synthesized by immobilizing 1-(2-thiazolylazo)-2-naphthol through the -N=N- group on Amberlite XAD-1180. The resin was used for the preconcentration of Cd(II), Co(II), Cu(II), Mn(II), Ni(II), and Pb(II) ions and their determination by flame atomic absorption spectrometry (FAAS). The influences of some analytical parameters, such as the pH, volume of the sample, flow rates of the sample and eluent, matrix components, amount of the resin, and amount and type of the eluent on the recovery, were investigated. Those metals retained on the resin at pH 8.5 were eluted with 25 mL of 2 mol L(-1) HNO(3). The sorption capacity of the resin was determined, except for Pb(II). The recoveries were found to be ≥95%, and the relative standard-deviation values were ≤4.3%. The detection limits were in the range of 0.1 - 3.6 µg L(-1). For the accuracy of the method, the analysis of a certified reference material was performed. This method was applied to environmental water samples.

Use of amidoximated hydrogel for removal and recovery of U(VI) ion from water samples.

Poly(acrylamidoxime-co-2-acrylamido-2-methylpropane sulfonic acid) (PAMSA) hydrogel was prepared by copolymerization of acrylonitrile and 2-acrylamido-2-methylpropane sulfonic acid as monomer, N,N'-methylenebis(acrylamide) as crosslinking agent and potassium peroxodisulfate as initiator. Amidoximated copolymer network was prepared by the reaction of copolymer network with hydroxylamine hydrochloride. A batch procedure was used for the determination of the characteristics of the U(VI) solid phase extraction from the amidoximated hydrogel. The determination of U(VI) was performed by spectrophotometric method using arsenazo-III as complexing agent. Optimal pH value for the quantitative preconcentration was 3, and full desorption was achieved with 3 mol L(-1) HClO(4). The adsorption process can be well described by the pseudo-second-order kinetic model, and the equilibrium adsorption isotherm was closely fitted with the Langmuir model. A preconcentration factor of 20 and the three sigma detection limit of 2.8 µg L(-1) (n=20) were achieved for uranium(VI) ions. The PAMSA hydrogel was used for separating and preconcentrating the uranyl ion existing in sea water samples, thermal spring water samples and the certified reference materials (TMDA 64; fortified lake water sample).

An on-line preconcentration/separation system for the determination of bismuth in environmental samples by FAAS.

An on-line preconcentration procedure for the determination of bismuth by flame atomic absorption spectrometry (FAAS) has been described. Lewatit TP-207 chelating resin, including iminodiacetate group, packed in a minicolumn was used as adsorbent material. Bi(III) was sorbed on the chelating resin, from which it could be eluted with 3 mol L(-1) HNO(3) and then introduced directly to the nebulizer-burner system of FAAS. Best preconcentration conditions were established by testing different resin quantities, acidity of sample, types of eluent, sample and eluent solution volumes, adsorption and elution flow rates, and effect of interfering ions. The detection limit of the method was 2.75 microg L(-1) while the relative standard deviation was 3.0% for 0.4 microg mL(-1) Bi(III) concentration. The developed method has been applied successfully to the determination of bismuth in pharmaceutical cream, standard reference materials and various natural water samples with satisfactory results.

Synthesis of a novel chelating resin and its use for selective separation and preconcentration of some trace metals in water samples.

A new chelating resin, poly[N-(4-bromophenyl)-2-methacrylamide-co-2-acrylamido-2-methyl-1-propanesulfonic acid-co-divinylbenzene], was synthesized and characterized. The resin was used for selective separation, preconcentration and determination of Cu(II), Ni(II), Co(II), Cd(II), Pb(II), Mn(II) and Fe(III) ions in water samples by flame atomic absorption spectrometry. Effects of pH, concentration and volume of elution solution, sample flow rate, sample volume and interfering ions (Na(+), K(+), Ca(2+), Mg(2+), Fe(3+), Mn(2+), Al(3+), Zn(2+), Pb(2+), Cu(2+), Ni(2+), Cd(2+), Cl(-) and SO(4)(2-)) on the recovery of the analytes were investigated. The sorption capacity of the resin was 25.6, 19.8, 32.1, 41.3, 38.9, 13.9 and 18.3 mg g(-1) for Cu(II), Ni(II), Co(II), Cd(II), Pb(II), Mn(II) and Fe(III), respectively. A high preconcentration factor, 100, and low relative standard deviation,

Synthesis of a novel chelating resin for the separation and preconcentration of uranium(VI) and its spectrophotometric determination.

A novel chelating polymer including three different functional groups, such as amidoxime (-C(NH(2))=NOH), azo (-N=N-) and carboxylic acid (-COOH), was synthesized. The poly(acrylamidoxime-co-(1-(2-pirydylazo)-2-naphtyl-2-methacrylate)-co-methacrylicacid) (APM) polymer, prepared in three steps, was characterized by FT-IR and elemental analyses. The resin was used for solid-phase extractive separation and the preconcentration of trace amounts of uranium(VI). The determination of U(VI) was performed by a spectrophotometric method using Arsenazo III as a complexing agent. The optimum conditions were found for the quantitative recovery of U(VI) (pH 5; eluent, 3 mol L(-1) HClO(4); sample and eluent flow rates, 1 mL min(-1) etc.). The capacity of the APM resin for U(VI) was found to be 24.2 mg g(-1). A preconcentration factor of 37.5 and the three sigma detection limit of 1.6 microg L(-1) (n = 20) were achieved for U(VI) ions. The polymer was used for separating and preconcentrating the uranyl ion existing in seawater samples and a certified reference material (TMDA 70; fortified lake water sample).

Solid phase extraction of Cu(II), Ni(II), Pb(II), Cd(II) and Mn(II) ions with 1-(2-thiazolylazo)-2-naphthol loaded Amberlite XAD-1180.

A new method for separation and preconcentration of trace amounts of Cu(II), Ni(II), Pb(II), Cd(II) and Mn(II) ions in various matrices was proposed. The method is based on the adsorption and chelation of the metal ions on a column containing Amberlite XAD-1180 resin impregnated with 1-(2-thiazolylazo)-2-naphthol (TAN) reagent prior to their determination by flame atomic absorption spectrometry (FAAS). The effect of pH, type, concentration and volume of eluent, sample volume, flow rates of sample and elution solutions, and interfering ions have been investigated. The optimum pH for simultaneous retention of all the metal ions was 9. Eluent for quantitative elution was 20 ml of 2 mol l(-1) HNO(3). The optimum sample and eluent flow rates were found as 4 ml min(-1), and also sample volume was 500 ml, except for Mn (87% recovery). The sorption capacity of the resin was found to be 0.77, 0.41, 0.57, and 0.30 mg g(-1) for Cu(II), Ni(II), Cd(II), and Mn(II), respectively. The preconcentration factor of the method was 200 for Cu(II), 150 for Pb(II), 100 for Cd(II) and Ni(II), and 50 for Mn(II). The recovery values for all of the metal ions were > or = 95% and relative standard deviations (RSDs) were < or = 5.1%. The detection limit values were in the range of 0.03 and 1.19 microg l(-1). The accuracy of the method was confirmed by analysing the certified reference materials (TMDA 54.4 fortified lake water and GBW 07605 tea samples) and the recovery studies. This procedure was applied to the determination of Cu(II), Ni(II), Pb(II), Cd(II) and Mn(II) in waste water and lake water samples.

Selective extraction, separation and speciation of iron in different samples using 4-acetyl-5-methyl-1-phenyl-1H-pyrazole-3-carboxylic acid.

A method for speciation, preconcentration and separation of Fe(II) and Fe(III) in different matrices was developed using solvent extraction and flame atomic absorption spectrometry. 4-Acetyl-5-methyl-1-phenyl-1H-pyrazole-3-carboxylic acid (AMPC) was used as a new complexing reagent for Fe(III). The Fe(III)-AMPC complex was extracted into methyl isobutyl ketone (MIBK) phase in the pH range 1.0-2.5, and Fe(II) ion remained in aqueous phase at all pH. The chemical composition of the Fe(III)-AMPC complex was determined by the Job's method. The optimum conditions for quantitative recovery of Fe(III) were determined as pH 1.5, shaking time of 2 min, 1.64x10(-4) mol L(-1) AMPC reagent and 10 mL of MIBK. Furthermore, the influences of diverse metal ions were investigated. The level of Fe(II) was calculated by difference of total iron and Fe(III) concentrations. The detection limit based on the 3sigma criterion was found to be 0.24 microg L(-1) for Fe(III). The recoveries were higher than 95% and relative standard deviation was less than 2.1% (N=8). The validation of the procedure was performed by the analysis of two certified standard reference materials. The presented method was applied to the determination of Fe(II) and Fe(III) in tap water, lake water, river water, sea water, fruit juice, cola, and molasses samples with satisfactory results.