Analysis of Toxic Aluminium Species in Natural Waters

Aluminium is known to be toxic to a wide range of aquatic organisms under certain conditions. Monomeric hydroxy ions have been found to be primarily responsible for aluminium aquatic toxicity.A survey of aluminium toxicity and a brief discussion of speciation schemes are presented. The fast reaction of Al³⁺ with pyrocatechol violet (PCV) followed by spectrophotometric analysis is a frequently used method for aluminium speciation. By using a flow system, one obtains fairly exact and reproducible control of the reaction time, and as a result it provides a direct method of analysis for free aluminium (including inorganic monomeric aluminium).The PCV-method has been adapted for the determination of aluminium in carbonate-rich natural waters using an improved buffering system. Thus it is possible to monitor aluminium concentrations in lake water as well as in pore water of the sediments of eutrophicated hardwater lakes that has been treated with aluminium salts as a restoration measure.     

Aluminium in the human brain

Abstract  

An inevitable consequence of humans living in the Aluminium Age is the presence of aluminium in the brain. This non-essential, neurotoxic metal gains entry to the brain throughout all stages of human development, from the foetus through to old age. Human exposure to myriad forms of this ubiquitous and omnipresent metal makes its presence in the brain inevitable, while the structure and physiology of the brain makes it particularly susceptible to the accumulation of aluminium with age. In spite of aluminium’s complete lack of biological essentiality, it actually participates avidly in brain biochemistry and substitutes for essential metals in critical biochemical processes. The degree to which such substitutions are disruptive and are manifested as biological effects will depend upon the biological availability of aluminium in any particular physical or chemical compartment, and will under all circumstances be exerting an energy load on the brain. In short, the brain must expend energy in its ‘unconscious’ response to an exposure to biologically available aluminium. There are many examples where ‘biological effect’ has resulted in aluminium-induced neurotoxicity and most potently in conditions that have resulted in an aluminium-associated encephalopathy. However, since aluminium is non-essential and not required by the brain, its biological availability will only rarely achieve such levels of acuity, and it is more pertinent to consider and investigate the brain’s response to much lower though sustained levels of biologically reactive aluminium. This is the level of exposure that defines the putative role of aluminium in chronic neurodegenerative disease and, though thoroughly investigated in numerous animal models, the chronic toxicity of aluminium has yet to be addressed experimentally in humans. A feasible test of the ‘aluminium hypothesis’, whereby aluminium in the human brain is implicated in chronic neurodegenerative disease, would be to reduce the brain’s aluminium load to the lowest possible level by non-invasive means. The simplest way that this aim can be fulfilled in a significant and relevant population is by facilitating the urinary excretion of aluminium through the regular drinking of a silicic acid-rich mineral water over an extended time period. This will lower the body and brain burden of aluminium, and by doing so will test whether brain aluminium contributes significantly to chronic neurodegenerative diseases such as Alzheimer’s and Parkinson’s.     

Isolation of Cyclic Aluminium Polysulfides by Stepwise Sulfurization

Despite the notable progress in aluminium chalcogenides, their sulfur congeners have rarely been isolated under mild conditions owing to limited synthetic precursors and methods. Herein, facile isolation of diverse molecular aluminium sulfides is achievable, by the reaction of N-heterocyclic carbene-stabilized terphenyl dihydridoaluminium ( 1 ) with various thiation reagents. Different to the known dihydridoaluminium 1^Tipp , 1 features balanced stability and reactivity at the Al center. It is this balance that enables the first monomeric aluminium hydride hydrogensulfide 2 , the six-membered cyclic aluminium polysulfide 4 and the five-membered cyclic aluminium polysulfide 6 to be isolated, by reaction with various equivalents of elemental sulfur. Moreover, a rare aluminium heterocyclic sulfide with Al−S−P five-membered ring ( 7 ) was obtained in a controlled manner. All new compounds were fully characterized by multinuclear NMR spectroscopy and elemental analysis. Their structures were confirmed by single-crystal X-ray diffraction studies.     

Influence of aluminium on the oxidation of titanium between 550 and 750 °C

In order to study the influence of aluminium on the oxidation resistance of titanium at high temperature, a range of binary alloys containing 1.65, 3, 5 and 10 wt.% of aluminium was prepared. Their oxidation kinetics were studied at temperatures between 500 and 750 °C using either continuous thermogravimetry or daily weighing for periods of up to several thousand hours. The results obtained for oxidation in air confirm the beneficial role of aluminium which has been observed previously for oxidation in oxygen. With regard to morphology and structure, aluminium modifies the internal structure of the oxide layers and their growth laws. A general dispersion of aluminium in rutile is observed, although a concentration of this phase is noted near the external interface; there is also a reduction in the amount of oxygen dissolved in the metal substrate which is related to the aluminium content in the alloy. Moreover, the presence of aluminium also modifies the adhesion of the oxide layers to the substrate.     

Corrosion mechanism of pure aluminium in aqueous alkaline solution

The corrosion of pure aluminium in alkaline solution has been explored using an open circuit potential transient, potentiodynamic polarization experiment and a.c. impedance spectroscopy. The steady-state value of the open circuit potential (E _ocp ^ss ) of pure aluminium in alkaline solution was observed to decrease with increasing rotation rate of the specimen, which is ascribed to the enhanced anodic reaction. The extent of anodic polarization for the aluminium dissolution reaction on pure aluminium at E _ocp ^ss was found to be greater than that of cathodic polarization for the water reduction reaction. This indicates that the rate of corrosion of pure aluminium is mainly determined by the anodic reaction in alkaline solution. Based upon the experimental results, a corrosion mechanism for pure aluminium has been proposed in the presence of the native surface oxide film in alkaline solution, involving consecutive oxide film formation and dissolution, and simultaneous water reduction.     

Determination of ochratoxin A in foods: state-of-the-art and analytical challenges

The work presented describes the application of different analytical approaches for study of aluminium mobility in rock, soil, and sediment samples affected by mining activity (secondary quartzites with sulfidic deposits). For this purpose we used a combination of the single extractions, the optimized BCR three-step sequential extraction procedure (SEP), and reactive aluminium determination after chelating ion-exchange on Ostsorb (Iontosorb) Salicyl by a batch technique with flame atomic absorption spectrometry quantification. The single extraction agents H₂O, KCl, NH₄Cl, and BaCl₂ were found to be the best for the quantitative estimation of the aluminium mobility in rocks, soils, and sediments caused by acidification of the environment. This fact was confirmed by reactive aluminium determination in the same samples. The vast majority of the aluminium content of samples after application of the optimized BCR three-step SEP is in the residues. The available fraction of aluminium extracted by dilute CH₃COOH in the first step of this procedure correlates with the reactive aluminium content. The amounts of aluminium released in the second and the third steps and the sums from steps 1–3 of this procedure are closely associated with the aluminium content values obtained by the single dilute HCl leach. The accuracy of results obtained was verified with only informative values for individual fractions of the BCR three-step SEP because of the absence of suitable certified or standard reference materials. The amounts of the reactive aluminium determined in samples was in the range 12–82% of total soluble Al in the filtered H₂O extracts. It was confirmed that the acidified polluted samples contain the most of reactive Al content, which is responsible for its toxicity.     

Reinforcing aluminium with cerium oxide: A new and effective technique to prevent corrosion in marine environments

Cerium oxide (CeO₂) is one of the potential choices to be explored for the protection of aluminium from corrosion. However, usage of cerium ions for surface modification of aluminium would not yield any potential effect in aggressive marine environments. Metal matrix composites of aluminium can have all the merits of aluminium such as density, strength, ductility and cost. In the present study, corrosion of aluminium in saline environment was significantly suppressed by means of reinforcing the aluminium with cerium oxide. The presence of cerium oxide in the matrix did not facilitate the formation of Al₂O₃ which would cause potential reshift after few days due to the onset of pitting. The present results strongly lay emphasis on the potential scope of use of CeO₂ for protection of aluminium in marine environments.     

Phosphorescence detection in flowing systems: selective determination of aluminium by flow-injection liquid room-temperature phosphorimetry

The concept of the micelle stabilized liquid room-temperature phosphorescence (MS-LRTP) was applied to the determination of a metal (aluminium) in a flowing system. A three-line flow-injection manifold was developed and various parameters were optimized. A linear calibration graph was obtained for 0–4 μg ml^?1 aluminium. The limit of detection was 50 ng ml^?1 and the relative standard deviations for 0.1 and 1.0 μg ml^?1 aluminium were 2.7 and 1.3% respectively. The proposed procedure is fairly selective. More than 20 common ions studied did not interfere with the determination of aluminium or could be masked by appropriate reagents. The flow-injection method proposed was applied without any preliminary separation to the determination of aluminium in simulated synthetic samples in water and in clinical samples of particular importance in the control of aluminium toxicity in renal failure patients.     

Atomic absorption spectrometric determination of aluminium in whole blood

Two methods are described for atomic absorption spectrometric determinations of aluminium m heparinized and haemolyzed samples of undiluted whole human blood. In the direct method 2μl of blood are pipetted into a graphite cup atomizer; after a drying and two ashing steps aluminium is determined by atomization at 2500°C. In the second method, 15μl of blood are decomposed by nitric acid in polytetrafluoroethylene tubes; 2-μl portions of the solution are then analyzed with the graphite tube atomizer. The direct method was applied to the determination of aluminium in whole blood from 48 Norwegian workers occupationally unexposed to the element; the concentrations of aluminium ranged from 0.05—0.59 p.p.m. (mean value, 0.20 p.p.m.). For 0.35 p.p.m. aluminium, the relative standard deviation of both methods was 8%. The detection limit of the direct method is 0.05 p.p.m. aluminium.     

Determination of aluminium in plutonium metal by differential linear sweep oscillographic polarography

A procedure has been developed for the polarographic determination of aluminium in plutonium. The plutonium is separated by anion-exchange in a nitrate medium, and the aluminium is determined in the eluate by use of Superchrome Garnet Y. The aluminium concentration range in the polarographed solutions is 0.020–0.800 μg/ml. The average recovery of aluminium was 99.3 %, relative standard deviation 7.2%. Of 20 common impurities found in plutonium métal, only molybdenum and titanium cause significant interference; both can be removed by ion-exchange.     

Structural study of VOx doped aluminium fluoride and aluminium oxide catalysts

The structural properties of vanadium doped aluminium oxyfluorides and aluminium oxides, prepared by a modified sol-gel synthesis route, were thoroughly investigated. The influence of the preparation technique and the calcination temperature on the coordination of vanadium, aluminium and fluorine was analysed by different spectroscopic methods such as Raman, MAS NMR and ESR spectroscopy. In all samples calcined at low temperatures (350 °C), vanadium coexists in two oxidation states V^IV and V^V, with V^IV as dominating species in the vanadium doped aluminium oxyfluorides. In the fluoride containing solids aluminium as well as vanadium are coordinated by fluorine and oxygen. Thermal annealing of 800 °C leads to an extensive reorganisation of the original matrices and to the oxidation of V^IV to V^V in both systems.     

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⁺.     

Dosage acidimétrique de l'ion aluminium

Acid titration of aluminium salts consists of two stages.1. Titration of the free acid. Complex ions are formed of aluminium with oxalatē of hydrofluorideions. 'I'he precipitation of aluminium hydroxide is retaided. Consequently the neutralisatiom of the free acid by the base is quite clear.2. Simultaneous titration of the acid and the aluminium ions. The solution with NaOH is neutralised until all the aluminium hydroxide is just precipitated. To avoid errors due to the formation of adsorption compounds, an excess of base is added and back-titrated with hydrochloric acid at the boiling point.These two titrations permit the determination of XXX acid and the aluminium content of the solution to approximately 0,3%.The influence of disturbing ions is studied.     

Spectrophotometric determination of aluminium with stilbazo

The use of stilbazo as a spectrophotometric reagent for aluminium has been investigated. The reagent forms a stable coloured complex with aluminium showing an absorption maximum at 500 mμ. The system obeys Beer's law from 0.1–0.8 p.p.m. aluminium. The molar extinction coefficient and the stoichiometric composition of the coloured complex have been determined.     

Aluminium speciation: Clinical and environmental aspects

The speciation of aluminium in serum and in water is discussed. Ultramicrofiltration and HPLC techniques have been used to show that > 90% of the aluminium in serum is non-ultrafiltrable and bound to the protein transferrin. Regarding the toxicity and speciation of aluminium in natural waters the literature is plagued by disparities. The present lack of designed protocols and reference waters for the determination of the toxic aluminium species is thought to play a key role in producing these disagreements.     

Simultaneous determination of lead, nickel, tin and copper in aluminium-base alloys using slurry sampling by electrical discharge and multielement ETAAS

The simultaneous multielement determination of Pb, Sn, Ni and Cu in aluminium alloys by electrothermal atomic absorption spectrometry (ETAAS) was performed by a quick method using slurry sampling. The metallic colloidal slurries were obtained by an electrical discharge operated in liquid medium. In this work, the effects of aluminium were evaluated and the results show that it causes a strong retention of Pb, Ni and Cu at low pyrolysis temperatures which is overcome by employing high pyrolysis temperatures. Aluminium also significantly improves the thermal stabilisation of Pb and Sn, it being possible to reach pyrolysis temperatures of 1100 and 1300 °C, respectively. Such stabilisation indicates that the performance of aluminium as a matrix modifier for Pb is better than that obtained using phosphate and magnesium nitrate without substantial changes of the figures of merit. The effects of aluminium on the atomisation characteristics of the elements and those coming from the simultaneous multielement determination on the figures of merit of the elements are also discussed. In this work, a calibration procedure involving a matrix matching method with aqueous aluminium standards is proposed as a simple and efficient way to solve the inconveniences originated by the aluminium matrix. The proposed method was applied to the simultaneous multielement determination of several aluminium-base alloy standards giving results well within the recommended values.     

Electron microscope investigations on the morphology of aluminium hydroxides

Summary The results are given of an investigation by means of the electron microscope and electron diffraction of the morphology of amorphous aluminium hydroxide and boehmite. The ageing process of amorphous aluminium hydroxide prepared from aluminium nitrate, ammonium alum and amalgamated aluminium was studied.

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Zusammenfassung Untersuchungen im Elektronenmikroskop und mit Elektronenbeugung über die Morphologie vom amorphen Aluminiumhydroxyd und B?hmit werden beschrieben. Die Alterung von amorphem Aluminiumhydroxyd, hergestellt aus Aluminiumnitrat, Ammoniumalaun und amalgamiertem Aluminium wurde untersucht.

     

The determination of aluminium by the ammonium benzoate method : An investigation into factors affecting the separation and estimation of aluminium and beryllium

An investigation has been made into the separation of aluminium from beryllium by the ammonium benzoate method. It has been shown (a) that over a wide range of concentrations aluminium can be determined with a maximum error of 2 %, (b) that the beryllium can be estimated after the removal of the aluminium with an error of not more than 2 % if the proportion of alumina, to beryllia is not more than 1 : 1. If the proportion of alumina to beryllia is greater than 1 : 1 considerable inaccuracy in the beryllium determination will result due to the co-precipitation of the beryllium with the aluminium benzoate; (c) that a double precipitation is required to obtain a satisfactory separation of aluminium and beryllium, (d) that although KoLTOFF el al. reported partial precipitation of beryllium with ammonium benzoate, this does not occur if tlie PH is carefully controlled between 3.5–4.0, and (e) it has been confirmed that ammonium benzoate precipitates aluminium quantitatively at PH 3.5ú4.0 wlilst beryllium does not commence to precipitate until about PH 6.5.     

Human diseases related to aluminium overload

Abstract  

In this paper attention is devoted to the role of aluminium in osteodistrophy and dialysis dementia. In fact, these diseases, in spite of the actions that have drastically reduced their occurrence, have so far constituted a cause of great medical concern. As a preliminary point, some aspects concerning the solution chemistry of aluminium are considered, then the medical problems are described and finally the chelation therapy of aluminium overload, giving some insight on the chelators recently proposed.     

Determination of aluminium and manganese in human scalp hair by electrothermal atomic absorption spectrometry using slurry sampling

Methods for the determination of aluminium and manganese in human scalp hair samples by electrothermal atomic absorption spectrometry using the slurry sampling technique were developed. Palladium and magnesium nitrate were used as chemical modifiers. Hair samples were pulverized using a zirconia vibrational mill ball, and were prepared as aqueous slurries. Determinations can be performed in the linear ranges of 1.9–150 μg l⁻¹ Al³⁺ and 0.03–10.0 μg l⁻¹ Mn²⁺. Limits of detection of 0.9 mg kg⁻¹ and 27.6 μg kg⁻¹ were obtained for aluminium and manganese, respectively. The analytical recoveries were between 99.6 and 101.8% for aluminium and in the 98.3–101.3% range for manganese. The repeatability of the methods (n=11), slurry preparation procedure and ETAAS measurement, was 16.0 and 7.9% for aluminium and manganese, respectively. The methods were finally applied to the aluminium and manganese determination in 25 scalp hair samples from healthy adults. The levels for aluminium were between 8.21 and 74.08 mg kg⁻¹, while concentrations between 0.03 and 1.20 mg kg⁻¹ were found for manganese.