Determination of trace metal ions Co,Cu, Mo,Mn, Fe,Ti, V in reference river water and reference seawater samples by inductively coupled plasma emission spectrometry combined with the third phase preconcentration

A combination of DAM-SCN^– third phase extraction and inductively coupled plasma emission spectrometry (ICP-AES) is used for the determination of trace metal ions in a river water and a seawater reference material. An implementation of the third phase extraction prior to ICP-AES allows a preconcentration of trace elements (Co, Cu, Mn, Fe, V, Ti, Mn) by a factor ranging from 33 to 45. A complete separation of these elements is accomplished from matrices, normally affecting the excitation characteristics of ICP and suppressing the elemental signals severely. Different factors, including pH of the solutions, amounts of reagents, matrix effects, have been investigated and optimized. Under the conditions selected, the limits of determination have been in the range of 0.02 to 0.6 g/L. The system has been successfully applied to the determination of Cu, Mn, V in the reference river water SLRS-3 and Mo in the reference seawater NASS-3. The results were in a good agreement with the certified values.     

Application of high-surface-area ZrO2 in preconcentration and determination of 18 elements by on-line flow injection with inductively coupled plasma atomic emission spectrometry

A flow-injection analysis (FIA) system incorporating a micro-column of ZrO2 has been used for the development of an on-line multi-element method for the simultaneous preconcentration and determination of Al, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, Mn, Mo, Ni, Pb, Tl, V, Sb, Sn, and Zn by inductively coupled plasma atomic emission spectrometry (ICP-AES). The conditions for quantitative and reproducible preconcentration, elution, and subsequent on-line ICP-AES determination were established. A sample (pH 8) is pumped through the column at 3 mL min(-1) and sequentially eluted directly into the ICP-AES with 3 mol L(-1) HNO3. With a sample volume of 100 mL and an elution volume of 1 mL signal enhancement 100 times better than for conventional continuous aspirating systems was obtained for the elements studied. The reproducibility (RSD %) of the method at the 10 ng mL(-1) level in the eluate is acceptable - less than 8% for five replicates. Recoveries between 95.4% and 99.9% were obtained for the elements analysed. ZrO2, with a specific surface area of 57 m2 g(-1) and a capacity of approximately 5 mg g(-1) for the elements studied, was synthesized by hydrolysis of ZrCl4. The preconcentration system was evaluated for several simple synthetic matrices, standard water samples and synthetic seawater. The effect of foreign ions on the efficiency of preconcentration of the elements studied was investigated. The application of a micro-column filled with high-surface-area ZrO2 and flow injection inductively coupled plasma atomic emission spectrometry enables preconcentration and simultaneous determination of 18 elements at low concentrations (ng L(-1)) in different water samples.     

Determination of trace elements in seawater by electrothermal atomic absorption spectrometry with and without a preconcentration step

The determination of the trace metals Cd, Pb and Cu in seawater by electrothermal atomic absorption spectrometry (ETA-AAS) has been investigated. A combination of the platform with mixed palladium nitrate-magnesium nitrate as matrix modifier and Zeeman background correction allows Cd an Pb to be determined by aqueous standard calibration in appropriately diluted seawater samples. Copper can be determined in undiluted seawater samples without chemical modification using a standard additions method. Detection limits (3) of 2.97,5.27 and 1.1 gl^–1 are obtained for Cd, Pb and Cu respectively. A Kelex-100 impregnated silica C18 material (Kelex 100-C18) has been tried and has proved to be effective as a column packing for extraction/preconcentration of these metals from seawater. Using the column extraction method, the sensitivity of the graphite furnace technique is enhanced 50-fold using a 10 l injection volume. Thus, the determination of the studied three metals in seawater at the ng.l^–1 level could be achieved.     

Solid-phase extraction of lead(II) ions using multiwalled carbon nanotubes grafted with tris(2-aminoethyl)amine

Multiwalled carbon nanotubes were grafted with tris(2-aminoethyl)amine (MWCNTs-TAA) and employed for solid phase extraction and preconcentration of trace lead ions prior to its determination by inductively coupled plasma optical emission spectrometry. The material was characterized by FT-IR and Raman spectroscopy, thermosgravimetric and elemental analysis. The effects of pH value, shaking time, sample volume, elution conditions and potentially interfering ions were investigated. Under the optimum conditions, the maximum adsorption capacity is 38?mg?g^?1 of Pb(II), the detection limit is 0.32?ng?mL^?1, the enrichment factor is 60, and the relative standard deviation is 3.5% (n?=?6). The method has been applied to the preconcentration of trace amounts of Pb(II) in environmental water samples with satisfactory results.

Novel phenyl-iminodiacetic acid grafted multiwalled carbon nanotubes for solid phase extraction of iron, copper and lead ions from aqueous medium

We have covalently grafted phenyl-iminodiacetic acid groups onto multi-walled carbon nanotubes via a diazotation reaction. The resulting material was characterized by FT-IR and UV–vis spectroscopy, by TGA, XPS and SEM. It is shown to be a valuable solid-phase extraction adsorbent for the preconcentration of trace quantities of Fe(III), Cu(II) and Pb(II) ion from aqueous solution prior to their determination by ICP-OES. Various factors affectting the separation and preconcentration were investigated. The enrichment factor typically is 100. Under optimized experimental conditions, the maximum adsorption capacities for Fe(III), Cu(II) and Pb (II) are 64.5, 30.5 and 17.0?mg?g-1, respectively, the detection limits are 0.26, 0.15 and 0.18?ng?mL-1, and the relative standard deviations are <2.5% (n?=?6). The new adsorbent shows superior reusability and stability. The procedure was successfully applied to the determination of trace quantities of Fe(III), Cu(II) and Pb (II) in water samples.

A novel approach for an automated liquid/liquid extraction system—principle and application for the determination of several trace contaminants in highly alloyed steels and base alloys

A novel automated liquid/liquid extraction system was developed for the determination of trace contaminants in unalloyed, alloyed and highly alloyed steels and super alloys. In the presented batch extraction system the aqueous phase and the non-water miscible organic phase were brought into close phase contact by high-speed stirring with a magnetic stir bar. Iodide complexes of Ag, Bi, Cd, Pb, Sb, Sn, Tl, and Zn were extracted from aqueous steel digests into 4-methylpentan-2-one (MIBK) containing 20 g L⁻¹ trioctylphosphine oxide. Ag, Bi, Cd, Pb, and Tl were extracted quantitatively whereas the extraction yields of Sb, Sn, and Zn were 83%, 61% and 75% respectively. Using high resolution continuum source flame AAS (HR-CS-FAAS) for analyte quantification the method was validated using 21 certified steel reference materials (CRMs).     

Multiwalled carbon nanotubes modified with 2-aminobenzothiazole modified for uniquely selective solid-phase extraction and determination of Pb(II) ion in water samples

A solid phase extraction method is presented for the selective preconcentration and/or separation of trace Pb(II) on multiwalled carbon nanotubes modified with 2-aminobenzothiazole. Inductively coupled plasma optical emission spectrometry was used for detection. The effects of pH, shaking time, sample flow rate and volume, elution condition and interfering ions were examined using batch and column procedures. An enrichment factor of 100 was accomplished. Common other ions do not interfere in both the separation and determination. The maximum adsorption capacity of the sorbent at optimum conditions is 60.3?mg?g^?1 of Pb(II), the detection limit (3??) is 0.27?ng?mL^?1, and the relative standard deviation is 1.6% (n?=?8). The method was validated using a certified reference material, and has been applied to the determination of trace Pb(II) in water samples with satisfactory results.

The Enrichment/Separation of Fe, Co, Pb, Cd, and Cr on Ambersorb 563 Prior to Their Flame Atomic Absorption Spectrometric Determinations

A sorbent extraction method for the separation/preconcentration of Fe, Co, Pb, Cd, and Cr was developed. The analyte metal ions were retained on a column of Ambersorb 563 from a buffered sample solution. The flow rates of the sample and eluent solution were controlled by a peristaltic pump. The analyte ions were quantitatively retained at pH 9 by using an ammonia/ammonium chloride buffer solution, and were then eluted with 5 mL of 0.25 M HNO₃ at 5 mL/min flow rate. The detection limits were in the range of 0.33 and 72 g/L for Cd and Pb, respectively. The relative standard deviations were less than 10%. Recoveries of spike addition to drinking water and seawater were quantitative. The method presented was applied for the determination of Fe, Co, Pb, Cd, and Cr ions in drinking and seawater samples with satisfactory results (recoveries >95%).     

An off-line automated preconcentration system with ethylenediaminetriacetate chelating resin for the determination of trace metals in seawater by high-resolution inductively coupled plasma mass spectrometry

A novel automated off-line preconcentration system for trace metals (Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in seawater was developed by improving a commercially available solid-phase extraction system SPE-100 (Hiranuma Sangyo). The utilized chelating resin was NOBIAS Chelate-PA1 (Hitachi High-Technologies) with ethylenediaminetriacetic acid and iminodiacetic acid functional groups. Parts of the 8-way valve made of alumina and zirconia in the original SPE-100 system were replaced with parts made of polychlorotrifluoroethylene in order to reduce contamination of trace metals. The eluent pass was altered for the back flush elution of trace metals. We optimized the cleaning procedures for the chelating resin column and flow lines of the preconcentration system, and developed a preconcentration procedure, which required less labor and led to a superior performance compared to manual preconcentration (Sohrin et al. [5]). The nine trace metals were simultaneously and quantitatively preconcentrated from ∼120 g of seawater, eluted with ∼15 g of 1 M HNO₃, and determined by HR-ICP-MS using the calibration curve method. The single-step preconcentration removed more than 99.998% of Na, K, Mg, Ca, and Sr from seawater. The procedural blanks and detection limits were lower than the lowest concentrations in seawater for Mn, Ni, Cu, and Pb, while they were as low as the lowest concentrations in seawater for Al, Fe, Co, Zn, and Cd. The accuracy and precision of this method were confirmed by the analysis of reference seawater samples (CASS-5, NASS-5, GEOTRACES GS, and GD) and seawater samples for vertical distribution in the western North Pacific Ocean.     

Separation and preconcentration of mercury in water samples by ionic liquid supported cloud point extraction and fluorimetric determination

We have developed a cloud point extraction procedure based on room temperature ionic liquid for the preconcentration and determination of mercury in water samples. Mercury ion was quantitatively extracted with tetraethyleneglycol-bis(3- methylimidazolium) diiodide in the form of its complex with 5,10,15,20-tetra-(4-phenoxyphenyl)porphyrin. The complex was back extracted from the room temperature ionic liquid phase into an aqueous media prior to its analysis by spectrofluorimetry. An overall preconcentration factor of 45 was accomplished upon preconcentration of a 20?mL sample. The limit of detection obtained under the optimal conditions is 0.08?μg mL^?1, and the relative standard deviation for 10 replicate assays (at 0.5?g mL^?1 of Hg) was 2.4%. The method was successfully applied to the determination of mercury in tap, river and mineral water samples.

Gas-stirred solvent extraction with propylene carbonate for separation and direct polarographic determination of thallium (III)

Gas-stirred propylene carbonate (PC) extraction can be performed by bubbling nitrogen without loss of volume. This extraction technique has proved to be highly useful for the separation and subsequent direct polarographic estimation of Tl(III) in the recovered PC phase. Tl(III) can be determined by differential-pulse polarography over the concentration range of 0.4 10 g ml^–1 without any interferences due to most metal ions such as Pb(II), Bi(III), Cu(II), Sb(III) and As(III). This proposed technique would be possible to use as a simple extraction step prior to the final estimation by instrumental method of analysis such as atomic absorption spectrometry or spectrophtometry.     

Determination of trace amounts of molybdenum in water samples by inductively coupled plasma atomic emission spectrometry after cobalt-dithiocarbamate coprecipitation

Summary A method for the determination of trace amounts of molybdenum in fresh water and seawater samples by sequential ICP-AES with microsampling technique after cobalt-dithiocarbamate coprecipitation was developed. The precipitate was dissolved in 100 l of diluted nitric acid (1:2), and the solution obtained was then introduced into an ICP via a concentric nebulizer. By use of 1.7 ml sample, a preconcentration factor of 17 was achieved. Different factors including integration time, sample volume, pumping rate as well as coprecipitation conditions such as pH of the solution, amounts of reagents, standing time for the precipitate and matrix effects were examined and optimized in detail. Under selected conditions the detection limit of the method for Mo is 0.52 g/l using 1.7 ml sample. The procedure was applied to the analysis of water samples (artificial water and open ocean seawater reference material) with quantitative recovery. The analytical results were in good agreement with the certified value. The method is sensitive, simple, accurate and effective, also in the presence of interfering salts and can be applied to small sample volumes.On leave from the Department of Chemistry, Wuhan University, Wuhan, 430072 China     

Simultaneous sample preconcentration and matrix removal using field-flow fractionation coupled to inductively coupled plasma mass spectrometry

An on-channel sample preconcentration-matrix removal arrangement, based on coupling field-flow fractionation (FFF) to inductively coupled plasma mass spectrometry (ICP-MS), has been constructed for on-line sample pretreatment ICP-MS trace element determination. A commercial FFF system is modified to incorporate an on-channel preconcentration procedure allowing injection of up to 50 ml of sample, which could be preconcentrated by 50–1400 fold. A high molecular weight complexing agent added to the sample forms strong complexes with the measured trace analytes but not with the sample matrix. When the sample-complexing agent mixture is introduced to the FFF unit, the uncomplexed matrix element is removed by permeation through a membrane that separates the FFF sample compartment. The trace analytes remain in the FFF channel, because their high molecular weight complexes do not permeate through the membrane. Preconcentration and matrix elimination occur simultaneously. The matrix-free, preconcentrated sample is introduced directly to the ICP-MS nebulizer. The method was tested using 10-ml sample aliquots that contain As, Cd, Cu, Mo, Pb, Re, Sn, Te, Tl, Y, Zn and Zr analytes and 5000 mg l⁻¹ Ca or Na matrices and ethylene imine polymer complexing agent. Copper and Re isotopic ratio values in reference standards also were determined after preconcentration and matrix element removal.     

LEAFS determination and concentration of metals in Great Lakes ecosystem

A Laser-Excited Atomic Fluorescence Spectrometric (LEAFS) method for Tl determination has been extended to investigate the direct determination (without preconcentration nor acid digestion) of total Pb, for which the method validation was successfully achieved by using a standard reference material as well as many spike recoveries of digested and undigested unfiltered water samples. The method was applied to study total and dissolved Pb in many water columns collected from different stations in Lake Ontario. Dissolved Pb was found to be about twice as much as dissolved Tl, and total Pb about seven times higher than total Tl. Seventy five percent of Pb is in particulate form versus 11% for Tl. Also, a simple cold dissolution procedure using HNO₃ and HF (not a hot acid digestion) is proposed to liquefy sediments in a form suitable for LEAFS analysis and was used to analyze a sediment core, where pore water samples were also collected. The interaction dynamics of Tl within the natural environment of a water/pore water/sediment system from Lake Erie was assessed. The calculations of fluxes suggest a strong similarity between Tl and Cd geochemical transport. The paper also presents for the first time a genuine sediment pore water profile of Tl concentration, which ranged from sub- to 40 ng/l and which was directly determined by LEAFS.     

Application of iminodiacetate chelating resin muromac A-1 in on-line preconcentration and inductively coupled plasma optical emission spectroscopy determination of trace elements in natural waters

On-line system incorporating a microcolumn of Muromac A-1 resin was used for the developing of method for preconcentration of trace elements followed by inductively coupled plasma (ICP) atomic emission spectrometry determination. A chelating type ion exchange resin has been characterized regarding the sorption and subsequent elution of 24 elements, aiming to their preconcentration from water samples of different origins. The effect of column conditioning, pH and flow rate during the preconcentration step, and the nature of the acid medium employed for desorption of the retained elements were investigated. A sample (pH 5) is pumped through the column at 3 ml min⁻¹ and sequentially eluted directly to the ICP with 3 M HNO₃/HCl mixtures. In order to remove residual matrix elements from the column after sample loading a short buffer wash was found to be necessary. The effectiveness of the matrix separation process was illustrated. The procedure was validated by analyzing several simple matrices, Standard River water sample as well as artificial seawater. Proposed method can be applied for simultaneous determination of In, Tl, Ti, Y, Cd, Co, Cu and Ni in seawater and for multielement trace analysis of river water. Recovery at 1 μg l⁻¹ level for the determination of investigated 24 elements in pure water ranged from 93.1 to 96% except for Pd (82.2%) and Pb (88.1%). For the same concentration level for seawater analysis recovery was between 81.9 and 95.6% except for Hg (38.2%).     

Preconcentration of trace lead via formation of the bis(2,2-bipyridyl) complex and its adsorption on oxidized multiwalled carbon nanotubes

A solid phase extraction method is presented for the preconcentration of trace lead ions on oxidized multiwalled carbon nanotubes (ox-MWCNTs). In the first step, the cationic Pb(II) complex of 2,2-bipyridyl is formed which, in a second step, is adsorbed on ox-MWCNTs mainly due to electrostatic and van der Waals interactions. The Pb(II) ions were then eluted with dilute nitric acid and quantified by FAAS. The effects of pH value, mass of sorbent, concentration of 2,2-bipyridyl, stirring time, of type, concentration and volume of eluent, of eluent flow rate and sample volume were examined. Most other ions do not affect the recovery of Pb(II). The limits of detection are 240 and 60 ng L^?1 for sample volumes of 100 and 400 mL, respectively. The recovery and relative standard deviation are >95 % and 2.4 %, respectively. Other figures of merit include a preconcentration factor of 160 and a maximum adsorption capacity of 165 mg g^?1. The method was successfully applied to the determination of Pb(II) in spiked tap water samples. The accuracy of the method was verified by correctly analyzing a certified reference material (NCS ZC85006; lead in tomatoes).

Trace analysis of rare earth elements and other impurities in high purity scandium by inductively coupled plasma mass spectrometry after liquid-liquid extraction of the matrix

Bis(2-ethyl hexyl)-orthophosphoric acid in toluene has been used to extract scandium selectively from an aqueous phase containing nearly thirty elements at various concentrations. The trace elements (Li, Mg, Al, Mn, Co, Ni, Cu, Zn, Ga, Sr, Y, Cd, In, Sb, Ba, REE, Hf, Pt, Tl, Pb, Bi and u) have been determined quantitatively in the aqueous phase using inductively coupled plasma mass spectrometry (ICP-MS). The recoveries have been quantitative for most of the analytes studied and ICP-MS has been found suitable for the determination of trace quantities of these elements in the aqueous extract. The procedure has been applied to the quantitative ultra-trace analysis of rare earth elements (REE) and other trace impurities in high purity scandium metal (4N) using ICP-MS and ID-ICP-MS techniques.Presented in part at the 2nd Regensburger Symposium Massenspektrometrische Verfahren der Elementspurenanalyse, 6.-8.10.93, Regensburg, Germany     

Comparison and evaluation of cloud point extraction and low-temperature directed crystallization as preconcentration tools for the determination of trace elements in environmental samples

A comparative study between cloud point extraction (CPE) and low-temperature directed crystallization (LTDC) is presented. Trace elements (Cd, Pb, Cr, Cu, Zn, Ni and Fe) were preconcentrated by both methods from model and natural water samples and the results were evaluated with respect to extraction efficiency, accuracy, precision, sample throughput and interferences. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used for the final measurements. The results indicate that these extraction and preconcentration procedures ensure the required accuracy and precision for the reliable identification and quantification of trace elements in natural waters. Drawbacks of each method identified can further assist the analyst towards a better application of each method depending on the target species, the detector employed and the application intended (routine analysis, trace analysis, speciation analysis, etc.).     

Nachweis und Bestimmung von Spuren toxikologisch wichtiger Metallionen mit Hilfe der Ringofenmethode

Zusammenfassung Es wird eine Methode zum Nachweis und zur Bestimmung von Metallen aus hochverdünnten Lösungen (Konzentrationsbereich 10^–4 bis 10^–7 Mol/l) beschrieben, bei welcher die Metallspuren zur Anreicherung gefÄllt, filtriert und mit Hilfe der Ringofenmethode auf Papierfilter übertragen werden.Das besonders für toxikologische Untersuchungen bestimmte spurenanalytische Verfahren ist sowohl für den qualitativen Nachweis von Cu, Cd, Sb, Pb, Bi, Hg, Fe, Zn, Mn, Cr und Tl geeignet (Nachweisgrenze in 5 ml Probelösung von 0,1–0,8 g), wie auch für die halbquantitative Bestimmung von Cu, Cd, Sb, Pb, Bi, Hg, Fe, Zn und Tl nach der Methode der Ringofentüpfelcolorimetrie.Die halbquantitativen Bestimmungen lassen sich noch mit insgesamt 4–8 g des entsprechenden Metalls in 10 ml Probelösung ohne Schwierigkeiten durchführen. Die Genauigkeit der Methoden entspricht den Anforderungen bei spurenanalytischen Untersuchungen.

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Summary A method for the identification and determination of metals from highly dilute solutions (concentrations of 10^–4–10^–7 Moles/l) is described; the traces of the metals are precipitated, filtrated and transferred to filter-paper by means of the ringoven method.This trace analytical procedure is especially determined for qualitative and semiquantitative toxicological investigations. Cu, Cd, Sb, Pb, Bi, Hg, Fe, Zn, Mn, Cr and Tl can be identified (identification limits between 0,1–0,8 g in 5 ml of test solution).The semi-quantitative determination of Cu, Cd, Sb, Pb, Bi, Hg, Fe, Zn, and Tl can likewise be carried out. 4–8 g only of the respective metal in 10 ml of test solution are needed. The reproducibility of the various determinations is satisfactory for trace analytical investigations.

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Herrn Prof. Dr. Ing. Fritz Feigl zum 75. Geburtstag herzlichst gewidmet.