Determination of aluminium in AlCl3 and Al2O3 modified silica catalyst supports

X-ray fluorescence spectrometry (XRF) was applied to determine aluminium in AlCl₃- and Al₂O₃-modified silica catalyst supports that were prepared by gas-solid reactions in an atomic layer epitaxy (ALE) process using aluminium chloride or aluminium chloride and water as adsorbates and silica as support. INAA and AAS were used as reference methods to determine the aluminium content of the supports. The calibration of XRF results was done by plotting the Al/Si intensity ratios against the aluminium content as determined by atomic absorption spectrometry (AAS) and verified by instrumental neutron activation analysis (INAA). Correlation factors for the calibration graphs were 0.984 for AlCl₃/SiO₂ and 0.995 for Al₂O₃/ SiO₂ samples in the aluminium content range 0–2.6 g Al per 100 g of sample. Received: 19 October 1998 / Accepted: 14 December 1998     

Determination of aluminium in AlCl3 and Al2O3 modified silica catalyst supports

X-ray fluorescence spectrometry (XRF) was applied to determine aluminium in AlCl₃- and Al₂O₃-modified silica catalyst supports that were prepared by gas-solid reactions in an atomic layer epitaxy (ALE) process using aluminium chloride or aluminium chloride and water as adsorbates and silica as support. INAA and AAS were used as reference methods to determine the aluminium content of the supports. The calibration of XRF results was done by plotting the Al/Si intensity ratios against the aluminium content as determined by atomic absorption spectrometry (AAS) and verified by instrumental neutron activation analysis (INAA). Correlation factors for the calibration graphs were 0.984 for AlCl₃/SiO₂ and 0.995 for Al₂O₃/ SiO₂ samples in the aluminium content range 0–2.6 g Al per 100 g of sample. Received: 19 October 1998 / Accepted: 14 December 1998     

Determination of trace metals in aluminium oxide by electrothermal atomic absorption spectrometry with direct injection of aqueous suspensions

Trace amounts (10^-5–10^-6% $\text{w}\text{w}$) of Ca, Cr, Cu, Fe, Na and Pb in aluminium oxide can be determined by graphite-furnace a.a.s. with injection of stirred sample suspensions into the tube. Calibration is possible either with Al₂O₃ standards for peak height and peak area measurements, or with standard solutions containing no aluminium for peak area measurements (except for copper). The analytical signals do not depend on the quantity of applied sample (0.02–1 mg Al₂O₃). Relative standard deviations are 2–6%.     

An evaluation of solid-state luminescence of chelates in trace metal analysis : The aluminium-oxine system

The potential of solid-state fluorescence analysis applied to metal-chelate systems is evaluated, with aluminium oxinate as a model. The coprecipitation of aluminium oxinate in excess of oxine. and measurement of the luminescence of the separated solid (λ_ex , 385 nm : λ_ex , 524 nm) allows the determination of 0.1 μg Al/sample (1 ng ml^?1 if 100-ml volumes available). Factors influencing the detection limit are discussed, and the interferences of several metals are determined. The requirements of a good reagent for general use are outlined.     

Adsorptive stripping voltammetric determination of cobalt at ppb levels in high-purity aluminium

Summary A sensitive procedure for the determination of cobalt in high-purity aluminium using DPCSV through adsorptive accumulation of Co(DMG)₂ on HMDE in triethanolamine + NH₄OH buffer is described. Analysis of NBS SRM C-1257 and a reactor grade aluminium sample is reported. Prior to the determination, cobalt was separated from Al and Ni on AG-1 X8 resin in 9 mol/l HCl. The results have been cross-validated by INAA.     

ETAAS determination of aluminium and copper in dialysis concentrates after microcolumn chelating ion-exchange preconcentration

A procedure was developed for the preconcentration and determination of aluminium and copper in dialysis concentrates at the ng cm^–3 level. The preconcentration was achieved on microcolumns filled with Chelex-100 resin adjusted to a pH of 4.0. Five repetitive cycles of the sample through the column ensured a sufficient contact time for quantitative retention of aluminium and copper ions. The retained ions were eluted with HNO₃ (0.5 mol dm^–3). Aluminium and copper were determined in the eluate by Zeeman ETAAS using the standard addition technique. The procedure was performed under clean room conditions (class 10,000), The reliability of the results was evaluated by recovery tests, using dialysis concentrates spiked with aluminium and copper. The recoveries obtained ranged from 86 to 106% for aluminium and from 92 to 97% for copper. Using the recommended procedure, the LOD of aluminium and copper in dialysis concentrates (preconcentration factor 2) was found to be 0.5 ng cm^–3 and 0.2 ng cm^–3, respectively. Received: 19 December 1997 / Revised: 10 March 1998 / Accepted: 28 March 1998     

ETAAS determination of aluminium and copper in dialysis concentrates after microcolumn chelating ion-exchange preconcentration

A procedure was developed for the preconcentration and determination of aluminium and copper in dialysis concentrates at the ng cm^–3 level. The preconcentration was achieved on microcolumns filled with Chelex-100 resin adjusted to a pH of 4.0. Five repetitive cycles of the sample through the column ensured a sufficient contact time for quantitative retention of aluminium and copper ions. The retained ions were eluted with HNO₃ (0.5 mol dm^–3). Aluminium and copper were determined in the eluate by Zeeman ETAAS using the standard addition technique. The procedure was performed under clean room conditions (class 10,000), The reliability of the results was evaluated by recovery tests, using dialysis concentrates spiked with aluminium and copper. The recoveries obtained ranged from 86 to 106% for aluminium and from 92 to 97% for copper. Using the recommended procedure, the LOD of aluminium and copper in dialysis concentrates (preconcentration factor 2) was found to be 0.5 ng cm^–3 and 0.2 ng cm^–3, respectively. Received: 19 December 1997 / Revised: 10 March 1998 / Accepted: 28 March 1998     

Speciation of aluminium fluoride complexes and Al in soils from the vicinity of an aluminium smelter plant by hyphenated High Performance Ion Chromatography Flame Atomic Absorption Spectrometry technique

The paper presents a new tool for the determination of inorganic speciation forms of aluminium: AlF_n^{(3 − n)+}, and Al³⁺ by means of the HPIC-FAAS. The proposed method has been successfully used for speciation analysis (qualitative and quantitative) of inorganic aluminium forms AlF_n^{(3 − n)+} in soil samples. In order to isolate the most environmentally available fraction, 5 g of the sample was collected and extracted in deionised water (water soluble fraction) for 1 h using a magnetic stirrer. The determinations in a hyphenated technique system were performed for a number of prepared water extracts. Concentration determinations of particular aluminium forms were performed based on model studies and real samples. The separation of Al species with nominal charge of + 1, + 2, and + 3 required a run time of less than 4 min during a single analysis. Based on the analysis of water extracts of soil, it was obtained that aluminium forms elute in the following order: 1PA (first signal) — AlF₂⁺ and/or AlF₄⁻; 2PA (second signal) — AlF²⁺ and/or AlF₃⁰; 3PA (third signal) — Al³⁺. In order to confirm the occurrence of these forms a simulation using the Mineql program was conducted. The details of speciation analysis of aluminium fluoride forms by means of an HPIC-FAAS instrument equipped are presented. Interpretation of the speciation analysis of the water soluble fraction of soil samples is proposed, based on the separation during chromatographic run and calculated data by Mineql.     

Complexometric determination of aluminium in iron ore,sinter, concentrates and agglomerates

A method for the complexometric determination of aluminium in iron ore, sinter, concentrates and agglomerates encountered in international trade is described. The sample is fused in a zirconium crucible with a mixed flux of sodium carbonate and sodium peroxide. The fused mass is completely soluble in hydrochloric acid. The R₂O₃ oxides are then precipitated with ammonia and redissolved in hydrochloric acid. Elements such as iron, titanium and zirconium are separated from aluminium by solvent extraction with cupferron and chloroform. After removal of traces of organic matter from the aqueous phase, the solution is treated with an excess of EDTA, which is then back-titrated with zinc solution (Xylenol Orange as indicator). Addition of ammonium fluoride then releases EDTA equivalent to the aluminium and this is titrated with zinc solution. The method is rapid. The precision and accuracy are excellent, and the results comparable with those obtained by the referee method.     

Simultaneous determination of aluminium,aluminium fluoride complexes and iron in groundwater samples by new HPLC–UVVIS method

The paper presents the application of the new HPLC–UVVIS method used in speciation analysis of aluminium form Al³⁺, aluminium complexes with fluorides and iron in groundwater samples. Based on the obtained results of groundwater samples analysis, the separation of iron in the retention time ≈ 3.7, was obtained. The conditions of the occurrence of particular aluminium forms based on the speciation analysis and modeling in the Mineql program were presented and confirmed. The influence of pH and ligand concentration on forming complexes was shown. The preliminary study of aluminium complexes with sulfates based on model solutions did not allow for the separation of the above complexes in presented analytical system. The paper presents the possible types of transformation of aluminium hydroxy forms and aluminium sulfate complexes by the reaction of the sample with mobile phase. An indirect method for the determination of aluminium in the form of aluminium sulfate was proposed. The new method was successfully applied in the determination of the following aluminium forms: Al³⁺, AlF₂⁺, AlF₃⁰, AlF₄^?, AlF²⁺ and Fe³⁺.     

Calibration of sputtering yields for AES depth profiling of oxide layers on aluminium by means of carrier-gas heat extraction analysis

Summary For the purpose of obtaining suitable reference materials for technical coatings on aluminium, the feasibility of calibration of oxide layers by means of heat extraction was studied. Oxide layers were prepared on aluminium sheets by immersion in water of 50 or 80 ° C and annealing at 500 or 600 °C in argon atmosphere. The layer thickness was calculated from the oxygen content of the sample as measured by carrier-gas heat extraction analysis.The total sputtering yield of aluminium oxide layers was obtained via the correlation of AES depth profiling with heat extraction analysis results. This was demonstrated for high purity (99.9%) and technical purity (98.5%) aluminium with its original roughness from the rolling process, on which 20 to 1,000 nm thick oxide layers had been grown.The sputtering yields for the oxide layers prepared were found to be 3.9±0.8 atoms/ion, i.e., about four times higher than that for -Al₂O₃. Calibration of depth profiling on such technical quality oxide layers on aluminium was found to be feasible with a relative precision of 10 to 20%.

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Kalibrierung der Ionenzerstäubung zur AES-Tiefenprofilanalyse von Oxidschichten auf Aluminium durch Trägergas-Heißextraktion

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On leave from the Institute of Photographic Chemistry, Academia Sinica, Beijing, People's Republic of China     

Speciation of trace amounts of aluminium in percolating water of forest soil by online coupling HPLC-ICP-MS

Procedures were developed for the speciation of trace amounts of aluminium present in percolating water of forest soil by online coupling of different chromatographic separation methods to an ICP-MS detection system. Inorganic and organic aluminium species were fractionated on a cation exchange column IONPAC CG12 (10-32). Phytotoxic polymeric aluminium hydroxides, as e.g. Al₁₃ (AlO₄Al₁₂(OH)₂₄(H₂O)₁₂ ⁷⁺), were determined using pyrocatechol violet (PCV) as a species dependant complexing reagent prior to the cation exchange step. Size fractionation of the organic aluminium species was obtained by size exclusion chromatography using the columns Superdex-75-HR 10/30 and Superdex-Peptide-HR 10/30. Validation of the speciation procedures proved that online coupling HPLC to the element selective and sensitive ICP-MS detection system leads to low detection limits of 0.3–0.6 μg/L and high precision and reproducibility (1.2–3.5%) of the speciation procedures. Speciation data determined for aluminium in a percolating water of the Zierenberg catchment are given.     

Determination of bismuth in geological materials by automated hydride generation and electrothermal atomic absorption spectrometry

The rapid and precise determination of bismuth (>5 μg kg^?1 in geological materials is described. The sample is decomposed with a HClO₄/HNO₃/HF mixture; interferences are eliminated by addition of aluminium chloride, ascorbic acid and thiourea. Bismuth hydride is introduced into a quartz cell atomizer.     

Speciation of trace amounts of aluminium in percolating water of forest soil by online coupling HPLC-ICP-MS

Procedures were developed for the speciation of trace amounts of aluminium present in percolating water of forest soil by online coupling of different chromatographic separation methods to an ICP-MS detection system. Inorganic and organic aluminium species were fractionated on a cation exchange column IONPAC CG12 (10-32). Phytotoxic polymeric aluminium hydroxides, as e.g. Al₁₃ (AlO₄Al₁₂(OH)₂₄(H₂O)₁₂ ⁷⁺), were determined using pyrocatechol violet (PCV) as a species dependant complexing reagent prior to the cation exchange step. Size fractionation of the organic aluminium species was obtained by size exclusion chromatography using the columns Superdex-75-HR 10/30 and Superdex-Peptide-HR 10/30. Validation of the speciation procedures proved that online coupling HPLC to the element selective and sensitive ICP-MS detection system leads to low detection limits of 0.3–0.6 μg/L and high precision and reproducibility (1.2–3.5%) of the speciation procedures. Speciation data determined for aluminium in a percolating water of the Zierenberg catchment are given. Received: 20 November 1998 / Revised: 28 January 1999 / Accepted: 3 February 1999     

Differential thermal analysis of the Al+20% (Fe-50%B) system

In the present study, aluminium and mechanically alloyed (36 h) Fe/B (50 wt%) are mixed. Al+20 (wt%) Fe/B mixture has been studied by differential thermal analysis to determine the aluminium quantity that is supposed to melt and afterwards does not solidify as it reacts with Fe/B powder. The different areas between endothermic reaction (melting peak) and exothermic reaction (solidification peak) allow in knowing the quantity of aluminium that reacts with Fe/B and the amount of intermetallic phases formed at high temperature. In order to follow the process, compacts were sintered at different temperatures (700, 800, 900, 1000 and 1200 °C), in N₂/10H₂/0.1CH₄ atmosphere. Microstructure was evaluated by image analysis and the results obtained by both techniques are compared.     

Comparative Study of the Acidity of Sulphated Zirconia Supported on Alumina Prepared by Sol-Gel and Impregnation Methods

Sulphated and unsulphated alumina-zirconia with atomic ratio Zr/Al = 0.5 were prepared by sol-gel and impregnation methods. The solid prepared by the sol-gel method exhibits the higher specific surface area. The Kelvin probe shows that the value of unsulphated sample is around 400 mV. This value grows up to 1100 mV for sample prepared by impregnation of aerogel alumina by sulphated propoxide zirconium and up to 1450 mV for sulphated alumina-zirconia aerogel catalyst. The modification of the work function is probably due to the charge transfer from the zirconium and aluminium to an oxygen species, responsible for the increase of Lewis acidity. XPS results show that the aluminium and zirconium exist in oxide form as Al₂O₃ and ZrO₂. The sulphur is present as sulphate species in the solids bonded to the Al—Zr—O framework. Furthermore, the oxygen species exist in different types created by the introduction of sulphur in the bulk of solids.Compared to the impregnated catalyst the sol-gel sulphated alumina zirconia exhibits higher activity in the isopropanol dehydration reaction in the temperature range 423 K–523 K.     

The determination of beryllium in geological and industrial materials by atomic-absorption spectrometry after cation-exchange separation

A method is described for the determination of beryllium in geological and industrial samples. After dissolution of the sample in mineral acids, beryllium is separated from the matrix elements by chloroform extraction of its acetylacetonate from a solution of pH 7 containing ascorbic acid and EDTA. Beryllium is separated from the organic extract and from co-extracted aluminium by means of a column of the strongly acidic cation-exchanger Dowex 50; beryllium is adsorbed from a medium consisting of 60 % (v/v) tetrahydrofuran, 30 % (v/v) chloroform and 10 % (v/v) methanol containing hydrochloric acid, aluminium is removed with 0.4 M oxalic acid and after elution with 6 M hydrochloric acid, beryllium is determined by atomic-absorption spectrometry with a nitrous oxide-acetylene flame. The method was used to determine p.p.m. and sub-p.p.m. quantities of beryllium in geochemical reference materials, U₃O₃ and yellow cake samples, and manganese nodules.     

Determination of AlN and Al2O3 in steels by electrolytic separation and wavelength dispersive X-ray fluorescence spectrometry

The determination of non-metallic aluminium inclusions in steel samples, mainly consisting of AlN and Al₂O₃, can be performed with the aid of their X-ray fluorescence K_β-line. The enrichment of these inclusions with an electrolytic isolation is described and shown to enable the analysis of samples with even very low aluminium content. The absolute detection limit of the combined electrolysis and X-ray fluorescence spectrometric detection using the Al-K_β line was found to be 3 μg Al in the residue that is below 0.001 mass-% in the steel sample under the given conditions. Due to low spectral resolution a deconvolution of the obtained data is required, but then a detection limit of 1.8 mass-% Al₂O₃ and 0.4 mass-% AlN in the binary mixture can be achieved. Sixteen samples of two low-alloyed steel qualities with a total amount of insoluble aluminium in the range of 0.003 to 0.013 mass-% have been analyzed with the procedure developed. Received: 11 February 2000 / Revised: 11 April 2000 / Accepted: 16 April 2000     

Structural studies of sialon ceramics by high-resolution solid-state NMR

High-resolution solide-state ²⁷Al NMR with magic-angle spinning (MASNMR) readily monitors the quantity and coordination (four- and six-fold) of aluminium in two ceramic materials of the SiAlON system. Sialon X-phase, of approximate composition Si₃Al₆O₁₂N₂, contains aluminium-centred octahedra and tetrahedra in the ratio ca. 1.9:1.0, while another sample containing a mixture of sialon polytypoids shows AlO₆ octahedra and a large quantity of what is most probably nitrogen-coordinated tetrahedral aluminium. In addition, ²⁹Si MASNMR detects two different kinds of silicon in the latter sample in a 2:1 ratio. These observations are interpreted satisfactorily in terms of the crystal structures of the compounds and provide further examples of the potential of MASNMR in the investigation of complex ceramic systems.     

Potentiometric microdetermination of aluminium in organic compounds after combustion in a modified oxygen flask

The microdetermination of aluminium in organic compounds by oxygen flask combustion, a simultaneous fusioncombustion procedure was developed, in which the sample in a mixture with KHSO₄ is burnt in a modified oxygen flask under suitable conditions so that the alumina formed is immediately converted into the corresponding water-soluble sulfate. 2.4 ml of 6M HCl are used as absorption solution, in which the combustion residue is completely dissolved by boiling. The solution is then transferred to a titration cell, neutralized with NaOH in the presence of methyl red, and the Al(III) is finally determined in a buffered 40% (V/V) dioxane solution by potentiometric titration with 0.1 M NaF. The results obtained were accurate within ±0.13%; the recoveries of Al are in the range of 99.00 to 99.90%; the standard deviation amounts to 0.06%. The potentiometric titration of Al(III) with fluoride as well as the conditions of the oxygen flask combustion of organic aluminium compounds are discussed.