AAS determination of trace elements in high-purity gold after matrix separation by solvent extraction

Summary A method is described for the determination of 20 trace elements in gold of a qualification of about 4–5 N. The matrix is separated by solvent extraction into methylethylketone/chloroform and the trace elements are determined in the aqueous phase by AAS (flame or graphite furnace). The procedure is optimized as to minimize the number of contamination sources.     

Candoluminescence-a new flame technique for trace analysis-I Development of a method for determination of bismuth

Early work on candoluminescence is reviewed and the phenomenon is investigated experimentally for the elements Bi, Mn, Sb and the lanthanides. It is demonstrated that it is feasible to determine bismuth (5-1000mug) by measuring its candoluminescent intensity at 399 nm, using a calcium hydroxide-calcium sulphate matrix and a hydrogen-helium-air flame.     

Reductive coprecipitation and extraction as separation methods for the determination of gold in copper concentrates by AAS and ICP-AES

Summary Simple methods for the determination of gold in copper concentrates are presented. Two separation procedures for gold are proposed. The first preconcentration procedure is based on the reductive coprecipitation of Au using part of the matrix copper as collector. The second implies selective quantitative extraction of Au using the extraction system 0.2 mol/l HCl/IBMK. Flame AAS or ICP-AES are used as instrumental methods and permit the determination of 0.1–50 g/g gold with a relative standard deviation of 3–12%.     

Radiochemical precipitation studies for separation of iodine from tellurium and other trace impurities

Precipitation of radiotellurium, containing trace radioimpurities, has been carried out from sulfate media at different pH-values. The highest precipitation yield was achieved at the region of pH ~4–6. Quantitative uptake by the formed precipitate was noticed for (i) ⁵⁴Mn, ^110mAg and ¹²⁵Sb over all the pH-range of study (pH 1.7–9.2), (ii) for ⁶⁵Zn and ⁶⁰Co in the regions of pH ~6–8 and pH 6–8.8, respectively, and (iii) for ¹³⁴Cs in the region of pH 1.7–2.8, while its percent uptake fluctuated around 60.5 % in the region of pH 4.4–6.4. Further precipitation studies have been conducted for a mixture of ¹²⁵I and radiotellurium from sulfate, nitrate and chloride media at pH-values of 6.0 and 7.5. The highest ¹²⁵I recovery yield in the obtained supernatant was 95.0 ± 1.3 %, which was achieved with sulfate medium at pH 6.0 with percent uptake values of 5.0 ± 1.3, 98.9 ± 0.9 and 62.0 ± 4.6 % of ¹²⁵I, ^123mTe and ¹³⁴Cs, respectively, and quantitative uptake of ⁵⁴Mn, ^110mAg, ¹²⁵Sb, ⁶⁰Co and ⁶⁵Zn by the precipitated tellurium. Thereafter, the supernatant was further acidified with H₂SO₄ and boiled, after adding H₂O₂, for 3 h. >99 % of ¹²⁵I was distilled off from the acidified supernatant. The distilled of ¹²⁵I was received in 0.1 M NaOH + 1 % Na₂S₂O₃ solution, with a radionuclidic purity of >99.99 %, radiochemical purity of >99.8 % as I^? and pH ~13.     

Neutron activation as a routine method for the determination of trace elements in water

By freeze-drying the following elements can be determined in natural water except sea water: Au, Ba, Br, Ca, Ce, Co, Cr, Eu, Fe, K, La, Mo, Na, Sb, Sc, Se, U, Zn. Some problems may arise with respect to As and Hg. Cu, Cd and Ni can only be determined if present in high concentrations. Separation by adsorption on charcoal in presence of complexing agents gives yields between 75 and 100% for the following elements in sea water: Ag, Au, Cd, Ce, Co, Cr, Eu, Fe, Hg, La, Mo, Sc, Se, U, Zn (As 67%, Sb 56%). Activation or use of labelled ions and study of exchange give information about mobility of trace elements in suspended matter.     

Sample introduction assisted by compressed air in flame furnace AAS: a simple and sensitive method for the determination of traces of toxic elements

The power of detection of flame AAS for the toxic elements Cd, Hg, Pb and Tl can be improved by 1–2 orders of magnitude by using flame furnace AAS. In flame-furnace AAS, liquid samples are introduced directly into a nickel tube located in the flame, in the simplest case through a ceramic thermospray capillary. Transportation of the samples is achieved by using compressed air only. Comparatively low detection limits are achieved by both beam injection flame furnace (BIFF-AAS) and thermospray flame furnace AAS (TS-FF-AAS). For TS-FF-AAS, a pressure of less than 20 kPa (<80 in. water) is required. The TS-FF-AAS technique is very simple, robust and cheap. The detection limits were 0.2–0.4 g L^–1 (Cd), 40–100 g L^–1 (Hg), 5–9 g L^–1 (Pb) and 4–14 g L^–1 (Tl), respectively, depending on the method, flow rate and sample volume used. Pb and Cd were found at concentrations of 0.1–2 and 0.005–0.3 g g^–1, respectively, in samples of various spices.Dedicated to the memory of Wilhelm Fresenius.     

A direct solid sampling electrothermal atomic absorption spectrometric method for determination of trace elements in zirconium dioxide

A direct solid sampling electrothermal atomic absorption spectrometric method for determination of Cd, Co, Cr, Cu, Fe, Li, Mn, Ni and Zn in zirconium dioxide has been developed. Using optimised experimental conditions, very effective in-situ analyte/matrix separation was achieved without any chemical modification. After the measurement, the matrix residue could easily be tipped out from the platform. In the determination of Cr, before sampling, the platform bottom was covered with carbon powder. Quantification was performed using calibration curves measured with aqueous standard solutions pipetted onto the matrix residue from a previous sample run. Sample amounts between 0.5 and 40 mg were applied for each analysis cycle. The accuracy was determined by comparison of the results with those obtained by radiochemical neutron activation analysis and by electrothermal atomic absorption spectrometry using liquid sampling of digests and slurry sampling. For the nine elements assayed, the limits of detection achievable by this method are between 0.06 ng g^–1 (Cd) and 2.3 ng g^–1 (Fe).Dedicated to the memory of Wilhelm Fresenius     

Determination of trace elements in Rheum moorcroftianum by AAS

Micro and macro elements such as Zn, Cu, Mn, Fe, Co, Na, K, Ca and Li were detected from Rheum moorcroftianum Royle, a plant used in folk medicines. Altitudinal and seasonal variation of these trace elements in cultivated and wild roots and leaves of R. moorcroftianum were quantified by atomic absorption spectroscopy. The highest concentrations of Zn, Cu, Mn, Fe, Co, Na, K, Ca and Li were found to be 376.0?±?0.9, 83.0?±?4.6, 322.0?±?6.0, 920.0?±?1.9, 72.0?±?1.5, 402.0?±?7.8, 10,235.0?±?7.0, 12,336.0?±?2.6 and 59.9?±?0.3 mg?kg(-1), respectively, in all the samples analysed.     

Reductive coprecipitation as a separation method for the determination of gold,palladium, platinum,rhodium, silver,selenium and tellurium in geological samples by graphite furnace atomic absorption spectrometry

A method for the separation of Au, Pd, Pt, Rh, Ag, Te and Se from geological samples at trace levels is presented. The elements are separated from the matrix after dissolution by reductive coprecipitation using mercury as a collector and tin(II) chloride as a reductant. The efficiency of coprecipitation is studied by varying the acidity of the solutions and the amount of collector. The analyte elements are determined by graphite furnace atomic absorption spectrometry. In the determination of volatile elements (Te, Au and Ag), matrix modification with iridium is used. Selenium is determined with a mixed matrix modifier containing ascorbic acid and iridium. The method is tested by analysing geochemical reference samples.     

The accurate determination of bismuth in lead concentrates and other non-ferrous materials by AAS after separation and preconcentration of the bismuth with mercaptoacetic acid

A method for determining 0.0001% and upwards of bismuth in lead, zinc or copper concentrates, metals or alloys and other smelter residues is described. Bismuth is separated from lead, iron and gangue materials with mercaptoacetic acid after reduction of the iron with hydrazine. Large quantities of tin can be removed during the dissolution. An additional separation is made for materials high in copper and/or sulphate. The separated and concentrated bismuth is determined by atomic-absorption spectrometry using the Bi line at 223.1 nm. The proposed method also allows the simultaneous separation and determination of silver.     

Hydraulic high-pressure nebulization sample introduction for direct analysis or on-line matrix separation and trace preconcentration in flame AAS

Summary Only by replacement of the pneumatic nebulization by the new hydraulic high-pressure nebulization (HHPN) in flame AAS 2 to 10 times higher power of detection (depending on the element) can be achieved for the direct trace determination in a saturated tungstate solution. HHP-nebulization leads in general to higher sensitivity and additionally to lower matrix interferences. The HHPN-sample introduction system offers also facilities for a quick on-line matrix separation/trace preconcentration. Detection limits of 0.1 to 1 g/g were achieved for a tungsten matrix (depending on the element).     

The development of a method for the determination of trace elements in fuel alcohol by electrothermal vaporization–inductively coupled plasma mass spectrometry using external calibration

A method for the determination of Ag, As, Cd, Cu, Co, Fe, Mn, Ni, Pb, Sn and Tl in fuel alcohol by electrothermal vaporization inductively coupled plasma mass spectrometry is proposed. The determinations were carried out by external calibration against ethanolic solutions, without a chemical modifier, employing the following pyrolysis and vaporization temperatures: 400 °C and 2300 °C for the more volatile analytes and 1000 °C and 2500 °C for the less volatile analytes. The determination of As, Cd, Pb, Sn and Tl was additionally carried out using Pd as modifier at 800 °C pyrolysis and 2400 °C vaporization temperatures. The temperatures were optimized through pyrolysis and vaporization curves. Seven common fuel ethanol, one fuel ethanol with additive and one anhydrous fuel ethanol sample have been analyzed. The measured concentrations were at the μg L⁻¹ level or lower. Since there is no certified reference material for fuel ethanol, the accuracy of the method was checked by the recovery test, with recoveries from 75% to 124%. The limits of detection (LODs), in μg L⁻¹, and the relative standard deviations for 5 replicates were, for the elements in the conditions without modifier: Ag: 0.015 and 9.1%, Co: 0.002 and 10%, Cu: 0.22 and 6.6%, Fe: 0.72 and 4.3%, Mn: 0.025 and 12%, Ni: 0.026 and 9.3%, and for the elements with Pd: As: 0.02 and 2.9%, Cd: 0.07 and 25%, Pb: 0.02 and 3.1%, Sn: 0.010 and 6.0%, Tl: 0.0008 and 2.5%. Electrothermal vaporization avoids the loading of the plasma with organics, allowing the analysis of fuel ethanol by ICP-MS with good accuracy and reasonable precision.     

Direct analysis of solids for trace elements by combined electrothermal furnace/quartz T-tube/flame atomic absorption spectrometry

The analysis of solid samples by a combined graphite-furnace/air-acetylene flame technique based on generally available atomic absorption instrumentation is described. Samples are injected into the furnace and atomized via a slotted T-tube in the flame. Non-specific absorption is greatly reduced compared to that obtained in graphite-furnace atomic absorption spectrometry (a.a.s.). Sensitivity is reduced by 10–200 times compared to the direct graphite-furnace method, so that large sample sizes (up to 0.2 g) can be used; this minimizes problems caused by sample inhomogeneity. The elements considered are cadmium, lead, copper, arsenic, cobalt, mercury, antimony and selenium. Volatile elements such as mercury and arsenic can be determined without the need for a char step. Simple calibration procedures are possible in some cases and the precision is usually better than 10%. Background reduction capabilities are compared with those of conventional graphite-furnace a.a.s., the isothermal-furnace and the hollow graphite T-tube techniques. Analytical capabilities and results are presented for the direct determination of trace elements in numerous biological and some geological samples.     

The use of electrothermal vaporization ICP-OES for the determination of trace elements in human hair using slurry sampling and PTFE as modifier

A procedure for the determination of trace elements in human hair has been proposed by electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) with slurry sampling. Slurry was prepared by immersing human hair with conc. HNO₃ and then adding a polytetrafluoroethylene (PTFE) slurry, which was used as a chemical modifier for the improvement of vaporization characteristic of analyte. The slurry was homogenized with an ultrasonic vibrator before the measurement. The vaporization behaviour of the analytes in slurry and solution and the main influence factors for the determination were studied with the addition of PTFE systematically. Detection limits for this method varied from 0.033?µg?g^?1 (Cu) to 3.21?µg?g^?1 (Zn) with the relative standard deviations (RSDs) of 2.8–7.1%. The proposed method was successfully applied for the determination of trace elements (Cu, Mn, Cr, Fe, Zn, Cd and Pb) in human hair with minimum chemical pretreatment and aqueous calibration. The accuracy was checked by comparing the results of this method with those using pneumatic nebulization (PN) ICP-OES after a conventional acid decomposition of the same sample. In addition, the standard reference material of human hair (GBW 07601) was analysed with good agreement between the results from the proposed method and the certified values.     

Preconcentration of trace elements in potable liquids by means of a liquid membrane emulsion for flame atomic absorption determination

Summary A liquid membrane emulsion was developed for the simultaneous extraction and preconcentration of traces of Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn in potable liquids. After preconcentration, the eight elements were determined by flame atomic absorption spectrometry (FAAS). The results of analyses of potable water, beer and soft drinks, each from five or six different sources are listed. Data from the preconcentration method were compared with corresponding data obtained from the direct determination of the elements by graphite furnace atomic absorption spectrometry (GFAAS). Differences in results for trace elements between the liquid membrane emulsion-FAAS method and the GFAAS method were in the ranges of ±10% (water), ±9% (beer) and ±14% (soft drinks) for most of the trace elements. The satisfactory agreement meant that analyses of such liquids for trace elements can be carried out accurately with less expensive and widely available FAAS equipment.     

Flame AAS/flame AES for trace determination in fresh and used lubricating oils with sample introduction by hydraulic high-pressure nebulization

In hydraulic high-pressure nebulization (HHPN) an aerosol is produced by means of an HPLC-pump and a special nebulization nozzle, applying a pressure of about 200 bar. This spray technique has been employed for sample introduction of mineral oil samples in flame atomic absorption/flame emission spectrometry. The determination of the trace elements Al, Cr, Cu, Fe, K, Na, Ni, Pb, Si and V has been investigated. Viscosity hardly acts upon the sensitivity of the determination, thereby avoiding a time consuming dilution of oil samples. By means of two interconnecting sampling valves a calibration method based on the standard addition technique can be performed which is both simple and easy to carry out. In samples of used oils, results for Cu and Pb equalled those of XRF-analysis. Regarding Fe traces, data obtained from AAS and XRF measurement correlate. In comparison with sample uptake by pneumatic nebulization, which is restricted to diluted oil samples, detection limits decrease by a factor of 2 to 4, indicating the dilution required in pneumatic nebulization.     

Emission-spectrometric determination of trace rare earth elements in europium oxide

Summary A dc arc excitation method in a controlled atmosphere was applied in the presence of CsCl-graphite (19) buffer for the quantitative determination of traces of rare earth elements in europium oxide. The intensities of the cyanogen band spectra and the background could be reduced by the use of argon-oxygen (41) mixed gas atmosphere and it was possible to obtain higher sensitivity than in the excitation in air. Addition of CsCl-graphite buffer causes an increase of the evaporation rate of the sample and of the number of atoms in the arc plasma, and the atoms and ions of rare earths distribute uniformly along the axis of the discharge gap. The buffer enhances the sensitivity and reproducibility and permits the determination of microquantities of 10 impurity elements within limits of detection from 3 to 11 ppm in high-purity europium oxide. The coefficients of variation are less than 13%.

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Emissionsspektrometrische Bestimmung von Spuren Seltener Erden in Europiumoxid

Zusammenfassung Die Anregung erfolgt im Gleichstrombogen in kontrollierter AtmosphÄre (Argon/Sauerstoff, 41) in Gegenwart eines CsCl-Graphit (19)-Puffers. Durch die Verwendung von Argon/Sauerstoff konnte die IntensitÄt des Untergrundes und der Cyanbanden erheblich reduziert und eine grö\ere Empfindlichkeit erreicht werden als bei der Anregung in Luft. Durch den Puffer wird die Verdampfungsgeschwindigkeit erhöht, die Anzahl der Atome im Bogenplasma vergrö\ert und eine gleichmÄ\ige Verteilung der Atome und Ionen lÄngs der Bogenachse erzielt. Empfindlichkeit und Reproduzierbarkeit werden verbessert. Spurenverunreinigungen von 10 Elementen können in hochreinem Europiumoxid bestimmt werden. Die Nachweisgrenzen liegen zwischen 3 und 11 ppm; der Variationskoeffizient ist < 13%.

     

Flame AAS/flame AES for trace determination in fresh and used lubricating oils with sample introduction by hydraulic high-pressure nebulization

In hydraulic high-pressure nebulization (HHPN) an aerosol is produced by means of an HPLC-pump and a special nebulization nozzle, applying a pressure of about 200 bar. This spray technique has been employed for sample introduction of mineral oil samples in flame atomic absorption/flame emission spectrometry. The determination of the trace elements Al, Cr, Cu, Fe, K, Na, Ni, Pb, Si and V has been investigated. Viscosity hardly acts upon the sensitivity of the determination, thereby avoiding a time consuming dilution of oil samples. By means of two interconnecting sampling valves a calibration method based on the standard addition technique can be performed which is both simple and easy to carry out. In samples of used oils, results for Cu and Pb equalled those of XRF-analysis. Regarding Fe traces, data obtained from AAS and XRF measurement correlate. In comparison with sample uptake by pneumatic nebulization, which is restricted to diluted oil samples, detection limits decrease by a factor of 2 to 4, indicating the dilution required in pneumatic nebulization.     

Group separation of trace rare-earth elements by countercurrent chromatography for their determination in high-purity calcium chloride

A method has been developed for the separation of the entire group of rare-earth elements from high-purity calcium chloride by countercurrent chromatography, and subsequent determination of the elements by ICP-MS. A solution of diphenyl[dibutylcarbamoylmethyl]phosphine oxide in chloroform (0.5 mol L(-1)) has been chosen as reagent for the extraction and preconcentration of trace rare-earth elements from aqueous 5% CaCl2 solution, 3 mol L(-1) in HNO3 and 0.1 mol L(-1) in HClO4. The analytes are back-extracted into a small volume of water and the aqueous eluate is subjected to ICP-MS measurements. The performance characteristics of the procedure developed have been checked by use of the standard addition technique and a real CaCl2 sample (Merck product) has been analyzed. The results obtained demonstrate the applicability of countercurrent chromatography to the determination of ultratrace elements.