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.     

Automated on-line separation preconcentration system for palladium determination by graphite furnace atomic absorption spectrometry and its application to palladium determination in environmental and food samples

A flow injection (FI) system was used to develop an efficient on-line sorbent extraction preconcentration system for palladium by graphite furnace atomic absorption spectrometry (GFAAS). The investigated metal was preconcentrated on a microcolumn packed with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide immobilized on silica gel (DPTH-gel). The palladium is eluted with 40 μl of HCl 4 M and directly introduced into the graphite furnace. The detection limit for palladium under the optimum conditions was 0.4 ng ml⁻¹. This procedure was employed to determine palladium in different samples.     

The possibility of standardless analysis in graphite furnace atomic absorption spectrometry: determination of gold in geological samples

This paper investigates the possibility of standardless analysis for gold in geological samples using graphite furnace atomic absorption spectrometry. A simplex optimization method is employed to select the optimum experimental conditions for both the conventional and fast furnace programs. The atomization efficiency (ε_A = 100 × m_0(calc)/m_0(exp)) for gold appears to be temperature dependent and is found to be around at 100% at higher atomization temperature. The results show that the standardless determination of gold could be performed in geological samples with the use of palladium as the matrix modifier and the accuracy is better than 7%.     

Direct determination of silver in geological reference samples after aqua regia leach by graphite furnace atomic absorption spectrometry with matrix modification

Summary Silver was determined in 20 different geological samples by electrothermal AAS with and without (NH₄)₂HPO₄ matrix modifier after aqua regia leach. The results were compared with those obtained after total dissolution of samples.The ashing temperature can be 300 °C higher and the atomising temperature 100°C lower when matrix modifier is used. The sensitivity of the method for Ag was 25% better with modifier. The detection limit, calculated in relation to the original solid sample, was 0.01 g/g with modifier.The results were systematically lower with matrix modifier, the mean value of recovery being 91.2% with modifier and 97.2% without. The ranges of the recovery values were noticeably different: from 84.5 to 99.5 with matrix modifier and from 63.4 to 110.2 without. The matrix modifier tended to even out the differences in the effects of geological matrices.

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Direkte Silberbestimmung in geologischem Referenzmaterial mit Hilfe der Graphitofen-AAS mit Matrixmodifikation (nach Auslaugen mit Königwasser)

     

Dispersive liquid-liquid microextraction preconcentration of palladium in water samples and determination by graphite furnace atomic absorption spectrometry

A new method for the determination of palladium was developed by dispersive liquid-liquid microextraction preconcentration and graphite furnace atomic absorption spectrometry detection. In the proposed approach, diethyldithiocarbamate (DDTC) was used as a chelating agent, and carbon tetrachloride and ethanol were selected as extraction and dispersive solvent. Some factors influencing the extraction efficiency of palladium and its subsequent determination, including extraction and dispersive solvent type and volume, pH of sample solution, concentration of the chelating agent and extraction time, were studied and optimized. Under the optimum conditions, the enrichment factor of this method for palladium reached at 156. The detection limit for palladium was 2.4 ng L⁻¹ (3σ), and the relative standard deviation (R.S.D.) was 4.3% (n = 7, c = 1.0 ng mL⁻¹). The method was successfully applied to the determination of trace amount of palladium in water samples.     

Preconcentration of palladium in a flow-through electrochemical cell for determination by graphite furnace atomic absorption spectrometry

An electrochemical preconcentration at a controlled potential on the electrode in a flow-through mode followed by graphite furnace atomic absorption spectrometric (GFAAS) detection is proposed for determination of trace amounts of palladium. After electrolysis the polarization of the electrodes was changed and deposited metal was dissolved electrochemically in the presence of an appropriate stripping reagent. Conditions for the electrodeposition, such as pH of the solutions, a deposition potential, dissolution potential and a composition of stripping solution were optimised. The graphite electrode (GE) and glassy carbon electrode (GCE) were tested for the palladium reduction process. The detection limit of 0.05 ng ml⁻¹ Pd (1 pg) was obtained after palladium preconcentration on the GCE and dissolution with 0.2 mol l⁻¹ thiourea in 0.1 mol l⁻¹ HCl followed by GFAAS detection. The method was applied for the determination of palladium in spiked tap water and road dust samples.     

流动注射在线分离富集-电热原子吸收法测定地球化学样品中的痕量金、铂、钯

建立了流动注射在线同时分离富集，无火焰原子吸收法测定地球化学样品中金、铂、钯的分析方法。研究了联用技术并进行了吸附条件和解脱条件的优化实验。当采样频率为20样/h时，Au、Pt、Pd的富集倍数分别为43、37、41。Au、Pt、Pd的检出限(3σ)分别为5、16、9ng／L。将Au、Pt、Pd质量浓度分别为50、200、100ng／L的混合标准溶液平行测定7次，求得Au、Pt、Pd的相对标准偏差分别为3．6％、5．1％、4．7％。并对国家级标准样品进行了测定，其结果及精密度符合要求。     

Displacement-dispersive liquid-liquid microextraction coupled with graphite furnace atomic absorption spectrometry for the selective determination of trace silver in environmental and geological samples

A novel displacement-dispersive liquid-liquid microextraction method was developed for the selective determination of trace silver in complicated samples by graphite furnace atomic absorption spectrometry. This method involves two steps of dispersive liquid-liquid microextraction (DLLME). Firstly, copper ion reacted with diethyldithiocarbamate (DDTC) to form Cu-DDTC complex and extracted with DLLME procedure using carbon tetrachloride (extraction solvent) and methanol (dispersive solvent); then, the sedimented phase was dispersed into the sample solution containing silver ion with methanol and another DLLME procedure was carried out. Because the stability of Ag-DDTC is larger than that of Cu-DDTC, Ag⁺ can displace Cu²⁺ from the pre-extracted Cu-DDTC and thus the preconcentration of Ag⁺ was achieved. Potential interference from co-existing transition metal ions with lower DDTC complex stability was largely eliminated as they cannot displace Cu²⁺ from Cu-DDTC complex. The tolerance limits for the co-existing ions were increased by a long way compared with conventional DLLME. Under the optimal conditions, the limit of detection was 20 ng L⁻¹ (3σ) for silver with a sample volume of 5.0 mL, and an enhancement factor of 72 was achieved. The proposed method was successfully applied to determine of trace silver in some environmental and geological samples with satisfactory results.     

Analytical potential of non-resonance lines for the determination of palladium by graphite furnace atomic absorption spectrometry

Summary Palladium is determined by graphite furnaceatomic absorption spectrometry. 8 non-resonance lines were studied, 4 of which have not been previously reported. The peak shapes and parameters of non-resonance lines are somewhat different from those of the resonance lines. The sensitivity of non-resonance transitions is found to be strongly dependent on the atomization temperature, heating rate of the graphite furnace as well as flow rate and nature of the purge gas used. The peak area sensitivity of the 340.5 nm nonresonance line almost equals that of the 276.3 nm resonance line.

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Analytische Möglichkeiten der Nichtresonanz-Linien für die Palladiumbestimmung durch Graphitofen-AAS

Zusammenfassung 8 Nichtresonanz-Linien wurden untersucht, von denen über 4 zuvor noch nicht berichtet wurde. Die Peakform und Parameter dieser Linien zeigen gewisse Unterschiede gegenüber denjenigen von Resonanzlinien. Die Empfindlichkeit ist stark von der Atomisierungstemperatur, der Aufheizgeschwindigkeit sowie der Geschwindigkeit und Art des verwendeten Spülgases abhängig. Die Peakflächenempfindlichkeit der Nichtresonanz-Linie 340,5 nm ist derjenigen der Resonanz-Linie 276,3 nm fast gleich.

     

Mechanism of modification by palladium in graphite furnace atomic absorption spectrometry

The effects of palladium and mixtures containing palladium on the absorbance characteristics of lead, thallium, cadmium, selenium, manganese and cobalt are described. These data, together with results of scanning electron microscopy showing the distribution of palladium on the graphite surface, indicate that palladium has a physical mechanism of analyte modification. During furnace heating, the analyte dissolves in molten palladium and may combine with it chemically. However, the rate limiting step leading to atomization appears to be diffusion of the analyte from palladium. The addition of magnesium, molybdenum or powdered carbon increases the speed of diffusion by causing palladium to form smaller droplets, and hence produces sharper absorbance peaks. Palladium becomes less effective as the atomization temperature increases, because the rate of diffusion is higher. This accounts for palladium having only a small stabilizing effect on less volatile elements such as manganese and cobalt. The addition of ascorbic acid to palladium has no significant effect on its modifying properties in a dilute nitric acid matrix. Results of kinetic studies on the atomization of gold are consistent with analyte diffusion out of palladium as the rate-limiting step leading to atomization.     

Single granular activated carbon microextraction and graphite furnace atomic absorption spectrometry determination for trace amount of gold in aqueous and geological samples

A new and simple method was developed for preconcentration trace amount of gold in aqueous and mineral samples. The method was based on the sorption of gold on granular activated carbon (AC) in acidic medium (hydrochloric acid) and subsequently direct determination by graphite furnace atomic absorption spectrometry (GFAAS). A small particle of adsorbent was delivered to small volume of sample. After extraction, AC removed and analyzed directly by GFAAS. Several factors influencing the extraction efficiency, such as the hydrochloric acid concentration, sample volume and extraction time were studied as well as effect of potential interfering ions. The preconcentration factor 50 was obtained. The limit of detection (LOD) of gold in water and soil samples was 0.007 μg L^− 1 and 0.9 ng g^− 1, respectively. The proposed method was applied successfully to the determination of trace amount of gold in environmental and geological samples. In order to validate the developed method, two certified reference materials: Platinum Ore (SARM-7B) and Copper Ore Mill Heads (No. 330) were analyzed and the determined values obtained were in good agreement with the certified values and recovery was obtained in the range of 80-118%. The relative standard deviations (RSD) for the spiking levels of 0.5 μg L^− 1 in the real samples was 4%, (n = 15).     

Optimization of the determination of selenium in marine samples by atomic absorption spectrometry: Comparison of a flameless graphite furnace atomic absorption system with a hydride generation atomic absorption system

A comparison has been made between a graphite furnace system based on nickel as a matrix stabilizing metal and an automated hydride generation system with a heated quartz cell. The effect of nickel as a matrix modifier was studied in pure selenite solutions as well as in biological matrixes by different charring temperatures. The suppression effect of different acids on the response of the analyte is reported and discussed. The use of an electrically heated quartz tube as an alternative to the argon hydrogen flame method unproved the selenium determination by hydride generation atomic absorption. The effect of hydrochloric acid to secure quantitative formation of selenium (IV) and the interference of copper in the response measurements have been studied. Further a comparison has been made between three different digestion procedures when the hydride generation atomic absorption system was applied. The results of the graphite furnace atomic absorption and the hydride generation atomic absorption were found to be equally accurate, but the graphite furnace technique gave better reproducibility.     

Modified carbon nanotubes as a sorbent for solid-phase extraction of gold,and its determination by graphite furnace atomic absorption spectrometry

A simple, sensitive and accurate method was developed for solid-phase extraction and preconcentration of trace levels of gold in various samples. It is based on the adsorption of gold on modified oxidized multi-walled carbon nanotubes prior to its determination by graphite furnace atomic absorption spectrometry. The type and volume of eluent solution, sample pH value, flow rates of sample and eluent, sorption capacity and breakthrough volume were optimized. Under these conditions, the method showed linearity in the range of 0.2–6.0 ng L⁻¹ with coefficients of determination of >0.99 in the sample. The relative standard deviation for seven replicate determinations of gold (at a level of 0.6 ng L⁻¹) is ±3.8 %, the detection limit is 31 pg L⁻¹ (in the initial solution and at an S/N ratio of 3; for n = 8), and the enrichment factor is 200. The sorption capacity of the modified MWCNTs for gold(III) is 4.15 mg g⁻¹. The procedure was successfully applied to the determination of gold in (spiked) water samples, human hair, human urine and standard reference material with recoveries ranging from 97.0 to 104.2 %.

A sorbent based on modified carbon nanotubes was prepared and used to extract gold ion from various samples prior to its determination by graphite furnace atomic absorption spectrometry

     

Evaluation of ammonia as diluent for serum sample preparation and determination of selenium by graphite furnace atomic absorption spectrometry

A method for the determination of total selenium in serum samples by graphite furnace atomic absorption spectrometry was evaluated. The method involved direct introduction of 1:5 diluted serum samples (1% v/v NH₄OH+0.05% w/v Triton X-100^®) into transversely heated graphite tubes, and the use of 10 μg Pd+3 μg Mg(NO₃)₂ as chemical modifier. Optimization of the modifier mass and the atomization temperature was conducted by simultaneously varying such parameters and evaluating both the integrated absorbance and the peak height/peak area ratio. The latter allowed the selection of compromise conditions rendering good sensitivity and adequate analyte peak profiles. A characteristic mass of 49 pg and a detection limit (3s) of 6 μg 1⁻¹ Se, corresponding to 30 μg l⁻¹ Se in the serum sample, were obtained. The analyte addition technique was used for calibration. The accuracy was assessed by the determination of total selenium in Seronorm™ Trace Elements Serum Batch 116 (Nycomed Pharma AS). The method was applied for the determination of total selenium in ten serum samples taken from individuals with no known physical affection. The selenium concentration ranged between 79 and 147 μg l⁻¹, with a mean value of 114±22 μg l⁻¹.     

石墨炉原子吸收法测定3-苯基丙烯酸酯类化合物中微量钯

利用高灵敏的石墨炉原子吸收法,在V(HCl):V(HNO3):V(H2O)＝5:1:94混合酸介质中测定苯基丙烯酸酯类化合物中的钯量.已纯化样品钯量的平均值是6.76 μg/g,标准相对偏差是4.8%,平均回收率为99.3%;未纯化样品钯量的平均值是121.2 μg/g,平均相对偏差是5.4%.还讨论酸介质对测定钯吸光度的影响,通过比较找到了合适的酸介质组成.     

An efficient combined procedure for the extreme trace analysis of gold, platinum, palladium and rhodium with the aid of graphite furnace atomic absorption spectrometry and total-reflection X-ray fluorescence analysis

Summary The determination of Au, Pt, Pd and Rh at ng- and pg-levels in manganese crust, natural water and geological and biological standards is based upon extraction of these elements with Se via a coprecipitation technique, elaborated as a micro-technique. All steps of the combined procedure are controlled by radiotracer (¹⁹⁵Au) and yields vary between 90 and 100%. Zeeman graphite furnace atomic absorption spectrometry and total reflection X-ray spectrometry are employed as determination steps. Sources of systematic errors are discussed.

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Leistungsfähiges Kombinationsverfahren zur Ultraspurenanalyse von Au, Pt, Pd und Rh mit Hilfe der GF-AAS und der Totalreflexions-Röntgenfluorescenzanalyse

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Dedicated to Prof. Dr. F. Huber on the occasion of his 60th birthday     

Determination of indium by graphite furnace atomic absorption spectrometry after coprecipitation with chitosan.

A sensitive and simple method for the determination of trace amounts of indium in water samples by graphite furnace atomic absorption spectrometry (GFAAS) after coprecipitation with chitosan was investigated. Indium was quantitatively preconcentrated from water samples by coprecipitation with chitosan at pH 7.0-9.0. The coprecipitant was easily dissolved with acetic acid, and indium in the resulting solution was determined by GFAAS. The addition of lanthanum as a chemical modifier was more effective for the atomic absorbance of indium. The detection limit (S/N > or = 3) for indium was 0.04 microg dm(-3), and the relative standard deviations (n = 5) were 3.5-4.5% at 1.0 microg/100 cm3. The results obtained in this study indicate that the proposed method can be successfully applied to the determination of trace indium in water samples.