Determination of trace amounts of gold in acid-attacked environmental samples by atomic absorption spectrometry with electrothermal atomization after preconcentration

A method for determination of trace amounts of gold in environmental samples (rocks, soils, sediments, and waters) by atomic absorption spectrometry with electrothermal atomization (ETAAS) after preconcentration using a chelating sorbent Spheron Thiol 1000 is described. The method accurately determines gold between 0.001 and several tens of grams per ton in samples having complex variations in mineralogy. Pulverized samples are roasted at 650°C to oxidize any sulfide and/or carbonaceous material. Samples are then subjected to a series of acid treatments to eliminate any silica matrix and to dissolve the sample. The Spheron Thiol 1000 is added to the sample solution, and then with sorbed gold is filtered out, washed, and ignited at 550°C. The residue is dissolved in aqua regia, evaporated, dissolved in distilled water, transferred to a volumetric flask, and analyzed by ETAAS.The limits of detection of gold, based on the 3 definition, were 0.5 ng g^–1 for 10-g samples (rocks, sediments, soils) and 0.05 ng mL^–1 for 1-L water samples. Precision of determination expressed by the relative standard deviation varied from 2.9% to 16.4%. The accuracy of the method is verified by analysis of certified reference materials. The obtained analytical results are in good agreement with attested values. The developed method was applied for gold determination in environmental samples affected by the acidification (acid mine drainage which is mainly a product of pyrite oxidation) from an open quartzite mine in the obov region situated NE of the city of Banská tiavnica (Slovakia).     

Determination of platinum and palladium in environmental samples by graphite furnace atomic absorption spectrometry after separation on dithizone sorbent

A graphite furnace atomic absorption method of platinum and palladium determination after their separation from environmental samples has been presented. The samples were digested by aqua regia and the analyte elements were separated on the dithizone sorbent. The procedure of sorbent preparation was described and their properties were established. Two various procedures of elution by thiourea and concentrated nitric acid were described and discussed. The low limit of detection was established as 1 ng g⁻¹ for platinum and 0.2 ng g⁻¹ for palladium.There was also investigated the behaviour of platinum and palladium introduced into the soil in various chemical forms.     

Determination of palladium and platinum by electrothermal atomic absorption spectrometry after deposition on a graphite tube

The inner wall of a pyrolytically coated graphite tube served as the surface for adsorptive accumulation and/or for electrodeposition of palladium and platinum. A flow system for this preconcentration was constructed. For the electrodeposition a three-electrode arrangement was used. The flow rate for deposition, the medium and deposition potentials were optimized. After the deposition step, the graphite tube was placed into the graphite furnace and an atomization programme was applied. The procedure was applied for the determination of Pd and Pt in airborne particulates.     

Flame atomic absorption spectrometry determination of trace amount of gold after separation and preconcentration onto ion-exchange polyethylenimine coated on Al2O3

The object of this work is to develop a simple and selective method for efficient extraction of Au(III) ions in aqueous solution using a new solid-phase extraction sorbent. Polyethylenimine (PEI) ion-exchange polymer was coated on alumina in the presence of NaNO₃. The method is based on sorption of Au³⁺ ions on 50 mg PEI/Al₂O₃. A solution of 0.5 M thiourea, then 1.0 M HCl effectively eluted the gold ion and then aspirated into flame atomic absorption spectroscopy (FAAS). The influence of flow rate of sample solution and eluent, the pH effect, eluent type and sorption capacity was investigated. The effects of various diverse ions for preconcentration and separation of the gold ion were investigated. Relative standard deviation of 4.0 μg mL⁻¹ of gold was 1.46% (n = 10). The detection limit was 26.2 ng L⁻¹ in original solution. The method has been applied successfully for the recovery of trace amount of Au(III) ions from water samples.     

析相微萃取-石墨炉原子吸收法测定地质样品中痕量金

以MIBK为络合剂和提取剂,乙醇为助溶剂,建立了析相微萃取-石墨炉原子吸收法测定地质样品中痕量金的分析方法。详细探讨了金的不同析相微萃取体系的特性及析相规律,优化了金-MIBK体系的最佳析相微萃取条件及石墨炉升温程序。所建立的方法线性范围为0.006~1.0μg/L,检出限为0.0013μg/L,相对标准偏差为1.5%(n=11),用于国家地质标准参考物质(GBW07289)的测定,分析结果与推荐值吻合。     

Ion-exchange method for separation and concentration of platinum and palladium for analysis of environmental samples by inductively coupled plasma atomic emission spectrometry

An ion-exchange procedure is proposed for determination of Pt and Pd in environmental samples, using a Dowex 1-X10 anion-exchange resin. Pt and Pd were separated from the matrix elements in the sample by selective retention on the column as anionic chloro complexes and subsequent elution by circulated thiourea at 60 °C. The eluent, containing Pt and Pd was analyzed by inductively coupled plasma (ICP) atomic emission spectrometry (AES). Average recoveries of 98% and detection limit of 15 ng/g for both metals were achieved. Analysis of Pt and Pd concentrations in road dust, sampled from several sites in Germany was performed. The comparison of the obtained data with the concentrations of Pt and Pd in the same samples, determined by ICP-MS showed a very good agreement.     

Determination of copper in water samples by atomic absorption spectrometry after cloud point extraction

Cloud point extraction employing the new reagent 6-[2′-(6′-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid as complexing agent and Triton X-114 as the surfactant is proposed for copper determination. A sample volume of 10 mL was used. Dilution of the surfactant-rich phase with acidified methanol was performed after phase separation, and the copper contents were measured by flame atomic absorption spectrometry. Variables affecting the system were optimized using factorial design and Doehlert matrix. Signals were measured as peak height using an instrument software. Using the experimental conditions defined in the optimization, the method allowed copper determination with a detection limit of 1.5 μg L⁻¹. The calculated enrichment factor is 14. The effects of foreign ions are reported. The accuracy of the procedure was tested by analyzing certified reference material. The method was successfully applied to copper determination in natural and drinking water samples.     

Determination of palladium in various samples by atomic absorption spectrometry after preconcentration with dimethylglyoxime on silica gel

A preconcentration method based on the adsorption of palladium-dimethylglyoxime (DMG) complex on silica gel for the determination of palladium at trace levels by atomic absorption spectrometry (AAS) has been developed. The retained palladium as Pd(DMG)₂ complex was eluted with 1 mol l⁻¹ HCl in acetone. The effect of some analytical parameters such as pH, amount of reagent and the sample volume on the recovery of palladium was examined in synthetic solutions containing street dust matrix. The influence of some matrix ions on the recovery of palladium was investigated by using the developed method when the elements were present both individually and together. The results showed that 2500 μg ml⁻¹ Na⁺, K⁺, Mg²⁺, Al³⁺ and Fe³⁺; 5000 μg ml⁻¹ Ca²⁺ ; 500 μg ml⁻¹ Pb²⁺; 125 μg ml⁻¹ Zn²⁺; 50 μg ml⁻¹ Cu²⁺ and 25 μg ml⁻¹ Ni²⁺ did not interfere with the palladium signal. At the optimum conditions determined experimentally, the recovery for palladium was found to be 95.3±1.2% at the 95% confidence level. The relative standard deviation and limit of detection (3s/b) of the method were found to be 1.7% and 1.2 μg l⁻¹, respectively. In order to determine the adsorption behaviour of silica gel, the adsorption isotherm of palladium was studied and the binding equilibrium constant and adsorption capacity were calculated to be 0.38 l mg⁻¹ and 4.06 mg g⁻¹, respectively. The determination of palladium in various samples was performed by using both flame AAS and graphite furnace AAS. The proposed method was successfully applied for the determination of palladium in the street dust, anode slime, rock and catalytic converter samples.     

Determination of platinum in alumina-supported automotive catalyst material by electrothermal atomic absorption spectrometry

Platinum (0.01–0.2%) is determined after dissolution in sulfuric and hydrochloric acids and addition of palladium and rhodium to compensate for interelement effects. At the 0.06% level, the relative standard deviation is 2%. The results agree within 4% with those obtained by chemical methods.     

Determination of lead, copper and manganese by graphite furnace atomic absorption spectrometry after separation/concentration using a water-soluble polymer

In this study, a water-soluble polymer, polyvinylpyrrolidinone (PVP) having chelating functionalities was used for the preconcentration and separation of traces of Pb, Cu, Ve and Mn prior to their determination by graphite furnace atomic absorption spectrometry. For this purpose, the sample and the PVP solutions were mixed and the metal bound polymer was precipitated by adding the mixture onto acetone. The precipitate was separated by decantation and dissolved with water. By increasing the ratio of the volumes of sample to water used in dissolving the precipitate, the analyte elements were concentrated as needed. The concentration of trace elements was determined using graphite furnace atomic absorption spectrometry. The analyte elements in matrix free aqueous solutions were quantitatively recovered. The validity of the proposed method was checked with a standard reference material (NIST SRM 1577b bovine liver) and spiked fruit juice, sea water and mineral water samples. The analytical results were found to be in good agreement with certified and added values. Detection limits (3δ) were 1.7, 3.6 and 4.1 μg l⁻¹ for Pb, Cu and Mn, respectively, using 10 μl of sample volume. The method is novel and can be characterized by rapidity, simplicity, quantitative recovery and high reproducibility.     

Determination of lead and nickel in Apple-Leaves and sea-water by electrothermal atomic absorption spectrometry after solid-phase extraction using Chromosorb-107 filled in a syringe

Lead and nickel were concentrated and separated after sorbing on Chromosorb-107 filled in a syringe prior to their determination by electrothermal atomic absorption spectrometry. To retain the analytes, the sample solution treated with or without ammonium pyrolidine dithiocarbamate (APDC) was drawn into the syringe filled with Chromosorb-107 and discharged back manually. Then the analyte elements were eluted by drawing and discharging the suitable eluent. The optimum experimental conditions for quantitative recoveries of analytes (amount of sorbent, pH of sample, concentration and kind of eluent, flow rates of sample and eluent and adding of the effect of complexing agent) were investigated. Nickel was quantitatively retained at pH6 irrespective of whether it was complexed with APDC while the quantitative sorption of lead was achieved at pH8 only if it was treated with APDC prior to passing through the sorbent. The lead and nickel retained on the sorbent were eluted drawing and discharging 4.5 M HNO(3), respectively. If the concentration of analyte elements in the sample were too low to be detected, then they were concentrated by increasing the ratio of sample value to eluent volume as needed. The lead and nickel in spiked sea-water samples and in certified reference Apple-Leaves (NIST SRM 1515) standards were quantitatively (95%) recovered with R.S.D. of around +/-2%.     

Determination of lead in aluminum and magnesium antacids using electrothermal atomic absorption spectrometry

This paper proposes a method for the determination of lead in aluminum and magnesium antacids employing electrothermal atomic absorption spectrometry (ET AAS). The pyrolysis and atomization temperatures established during the optimization step were 700 and 2200 °C, respectively, using phosphate as the chemical modifier. Under these conditions, a characteristic mass of 25 pg, and limits of detection and quantification of 0.40 and 1.35 μg L⁻¹, respectively were obtained. Some experiments demonstrated that the calibration can be performed employing the external calibration technique using aqueous standards. The precision expressed as relative standard deviation (RSD %) was 4.03% for an antacid sample with lead concentrations of 284.5 μg L⁻¹. The proposed method was applied for the determination of lead in five antacid samples acquired in Salvador City, Brazil. The lead content was varied from 87 to 943 μg g⁻¹. The samples were also analyzed after complete dissolution by inductively coupled plasma mass spectrometry (ICP-MS). No statistical difference was observed between the results obtained by both of the procedures performed.     

Determination of palladium and platinum by atomic absorption

Palladium and platinum are determined by atomic absorption after fire-assay concentration into a gold bead. The limit of determination is ~0.06 ppm in a 20-g sample. Serious depressive interelement interferences are removed by buffering the solutions with a mixture of cadmium and copper sulphates with cadmium and copper concentrations each at 0.5%. Substantial amounts of Ag, Al, Au, Bi, Ca, Co, Cr, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn, and the platinum metals do not interfere in the atomic-absorption determination.     

Determination of Cd by electrothermal atomic absorption spectrometry after electrodeposition on a graphite probe modified with palladium

Traces of Cd were determined by electrothermal atomic absorption spectrometry after electrochemical preconcentration on a commercial graphite ridge probe modified with Pd. The Pd electrochemically deposited on the probe surface served not only as the modifier but it also protected the graphite surface. Cd was electrodeposited at a controlled potential − 1.2 V (vs. saturated calomel electrode) using the Pd-modified graphite probe as a working electrode. The sensitivity of Cd determination remained unchanged for 300 electrodeposition and atomization cycles. The detection limit (3σ_blank) was improved with increasing time of electrolysis and was 1.2 ng l^− 1 for a 10 min electrolysis time in the presence of 0.1 mol l^− 1 NaNO₃. The procedure was applied for the determination of Cd in (1 + 1) diluted seawater and in (1 + 1) diluted urine samples using the standard addition method.     

Determination of nanogram amounts of cadmium in water by electrothermal atomic absorption spectrometry after flotation separation

A method is described for the flotation an determination of ng-levels of cadmium in water. Cadmium in a 1-l sample of water is coprecipitated with hydrated zirconium oxide at pH 9.1 ± 0.1. The precipitate is floated with the aid of a surfactant solution and small air bubbles, separated and dissolved in dilute hydrochloric acid. The cadmium content is determined by electrothermal atomic absorption spectrophotometry. The method is applied to the determination of ng l^?1 levels of cadmium in fresh water. The time required for preconcentration of cadmium from a 1-l sample is 20 min per sample, after 20 min stirring.     

Assessment of immobilized yeast for the separation and determination of platinum in environmental samples by flow-injection chemiluminescence and electrothermal atomic absorption spectrometry

The yeast Saccharomyces cerevisiae immobilized in calcium alginate beads was used for separation and subsequent determination of Pt in environmental samples by flow-injection chemiluminescence (FI-CL) and electrothermal atomic absorption spectrometry (ETAAS). The application of a yeast column resulted in an increase in the tolerable matrix ions concentration compared to direct measurements by both detection techniques. The developed FI-CL method of Pt determination based on the catalytic effect of Pt(IV) ions on luminol oxidation in alkaline medium is characterized by a low limit of detection (0.15 ng mL^?1), and good sensitivity and precision, and can be used for analysis of Pt in water samples. Determination of Pt in more complex environmental samples can be carried out by ETAAS (LOD?=?6 ng mL^?1) after introduction of a column clean-up step with 10 mM nitric acid. The accuracy of the method was confirmed by analyzing the certified reference material of platinum ore (SARM-7), spiked grass, and road dust samples.     

The determination of platinum and palladium in rocks and soils by electrothermal atomic absorption spectrometry of extracts of their iodo complexes

The method developed for determining platinum and palladium in rocks and soils is based on extraction of iodo complexes of these elements into methyl isobutyl ketone (MIBK), followed by electrothermal atomic absorption spectrometry of the extracts. The limit of detection is 10 ng g^?1 for platinum and 3 ng g^?1 for palladium. Analysis of the standard noble metal ore PTC-1 with recommended values of 12.7 μg g^?1 for palladium and 3.0 μg g^?1 for platinum gave precisions of 4.4% and 5.6%, respectively, and deviations of 5.0% and 1.2% from the recommended values. The method is applicable to the determination of both elements in a wide variety of rocks and soils.     

Determination of ultra trace amounts of bismuth in biological and water samples by electrothermal atomic absorption spectrometry (ET-AAS) after cloud point extraction

A new approach for a cloud point extraction electrothermal atomic absorption spectrometric method was used for determining bismuth. The aqueous analyte was acidified with sulfuric acid (pH 3.0-3.5). Triton X-114 was added as a surfactant and dithizone was used as a complexing agent.After phase separation at 50 °C based on the cloud point separation of the mixture, the surfactant-rich phase was diluted using tetrahydrofuran (THF). Twenty microliters of the enriched solution and 10 μl of 0.1% (w/v) Pd(NO₃)₂ as chemical modifier were dispersed into the graphite tube and the analyte determined by electrothermal atomic absorption spectrometry. After optimizing extraction conditions and instrumental parameters, a preconcentration factor of 196 was obtained for a sample of only 10 ml. The detection limit was 0.02 ng ml⁻¹ and the analytical curve was linear for the concentration range of 0.04-0.60 ng ml⁻¹. Relative standard deviations were <5%.The method was successfully applied for the extraction and determination of bismuth in tap water and biological samples (urine and hair).     

Evaluation of different permanent modifiers for the determination of arsenic in environmental samples by electrothermal atomic absorption spectrometry

Single noble metal permanent modifiers such as, Rh, Ir, and Ru, as well as mixed tungsten plus noble metal (W-Rh, W-Ru, W-Ir) permanent modifiers thermally deposited on the integrated platform of transversally heated graphite atomizer were employed for the determination of arsenic in sludges, soils, sediments, coals, ashes and waters by electrothermal atomic absorption spectrometry. Microwave digests of solid samples and water samples were employed for obtaining the analytical characteristics of the methods with different permanent modifiers. The performance of the modifiers for arsenic determination in the real samples depended strongly on the type of permanent modifier chosen. The single noble metal (Rh, Ir and Ru) permanent modifiers were suitable for the analyte determinations in simpler matrices such as waters (recoveries of certified values 95-105%), but the analyte recoveries of certified values in sludges, soils, sediments, coals, and ashes were always lower than 90%. On the other hand, for the determination of arsenic, using W-Rh, W-Ru, and W-Ir permanent modifiers presented recoveries of certified values within 95-105% for all the samples. Long-term stability curves obtained for the determination of arsenic in environmental samples with different permanent modifiers (Rh, Ir, Ru, W-Rh, W-Ir, W-Ru) showed that the improvement in the tube lifetime depends on the tungsten deposit onto the platform. The tungsten plus noble metal permanent modifier presents a tube lifetime of at least 35% longer when compared with single permanent modifier. The results for the determination of As employing different permanent modifiers in the samples were in agreement with the certified reference materials, since no statistical differences were found after applying the paired t-test at the 95% confidence level.     

Determination of cadmium by electrothermal atomic absorption spectrometry using electrochemical separation in a microcell

Electrodeposition on the graphite electrode under conditions of controlled current in a flow-through mode, followed by electrothermal atomic absorption spectrometry, is proposed for the determination of cadmium. After electrolysis in a microcell of 2.6 μl volume, deposited metal was dissolved in 40 μl 0.2 mol l⁻¹ HNO₃ and the whole volume was direct injected into the atomizer. Using this on-line arrangement and electrodeposition from 1.75 ml of sample solution detection limit of 25 ng l⁻¹ Cd was attained. The method was applied for the determination of cadmium in a real sample of seawater.