Determination of aluminium and chromium in slurried baby food samples by electrothermal atomic absorption spectrometry

Electrothermal atomic absorption spectrometry was used to determine aluminium and chromium in different types of baby foods. Samples without previous treatment were introduced into the atomizer as suspensions, which were prepared in a medium containing 0.1% (w/v) Triton X-100 (for chromium) or 10% (v/v) ethanol (for aluminium), 5% (v/v) concentrated hydrogen peroxide, and 0.5% (v/v) concentrated nitric acid. The slurries were homogenized with a potter and introduced directly into the furnace. The presence of nitric acid allowed a substantial amount of analyte to be extracted to the liquid phase. No matrix effect was observed and aqueous standard solutions were used for calibration. The detection limits were 4 and 50 pg for chromium and aluminium, respectively; characteristic masses were 3.8 pg for chromium and 18 pg for aluminium. Reliability of the procedures was checked by statistically comparing the results with those obtained with a previous microwave oven mineralization stage and by analyis of several certified reference materials. Values for the aluminium content ranged between 0.4 and 3.0 microg/g, and for chromium between 0.003 and 0.06 microg/g.     

Titrimetric, coulometric and spectrophotometric determination of manganese following perchloric acid oxidation in the presence of pyrophosphate

Manganese is oxidized quantitatively to a violet, tervalent pyrophosphate in a boiling mixture of equal parts of perchloric acid and phosphoric add. This Mn(III) can be titrated potentiometrically or coulometrically with iron(II); it can also be measured spectrophotometrically. If the titrimetric method is carried out with titanium (III) or chromium(II), iron can also be titrated immediately after the manganese. The methods were applied to a new reference sample, ISU 600 Manganiferous Iron Ore, and to manganese ore, spiegeleisen, ferromanganese, and rail steel. Manganese(II) oxalate dihydrate has been reinvestigated as a primary standard and is highly recommended.     

A new method for the direct precipitation of aluminium in the presence of iron

It is shown that aluminium can be precipitated as benzoate from solutions containing up to 1 gram of iron in the presence of thioglycollic acid, which reduces the iron and forms a soluble complex with ferrous iron. Very large amounts of such salts as ammonium chloride, sulphate and perchlorate, and sodium chloride do not interfere, nor do other divalent metals. Molybdates and tungstates are without effect, but chromium, vanadium and titanium interfere. This limits the direct application of the method in metallurgical analysis, but in many cases this speedy and complete separation will have many uses.     

Determination of chromium in ores, rocks and related materials, iron, steel and non-ferrous alloys by atomic-absorption spectrophotometry after separation by tribenzylamine-chloroform extraction

A method for determining trace and moderate amounts of chromium in ores, concentrates, rocks, soils and clays is described. After fusion of the sample with sodium peroxide, the melt is dissolved in dilute sulphuric acid. The chromium(III) produced by the hydrogen peroxide formed is co-precipitated with hydrous ferric oxide. The precipitate is dissolved in 0.7M sulphuric acid and chromium oxidized to chromium(VI) with ceric ammonium sulphate. The chromium(VI) is extracted as an ion-association complex into chloroform containing tribenzylamine and stripped with ammoniacal hydrogen peroxide. This solution is acidified with perchloric acid and chromium determined by atomic-absorption spectrophotometry in an air-acetylene flame, at 357.9 nm. Barium and strontium do not interfere. The procedure is also applicable to iron and steel, and nickel-copper, aluminium and zirconium alloys. Up to 5 mg of manganese and 10 mg each of molybdenum and vanadium will not interfere. In the absence of vanadium, up to 10 mg of tungsten will not interfere. In the presence of 1 mg of vanadium, up to 1 mg of tungsten will not interfere.     

The determination of tervalent chromium and iron in chromic acid

Chromic acid is analysed for tervalent chromium by separation of Cr(III) from Cr(VI) by precipitation as the hydrous oxide, with Zn(OH)(2) as a carrier. The hydrous oxide is collected by centrifugation and dissolved in perchloric acid, then Cr(III) is complexed with 1,2-diaminocyclohexanetetra-acetic acid and measured spectrophotometrically at 540 mmicro. Repetitive analysis of a sample of chromic acid showed 93 ppm of Cr(III) (s = 13, n = 9). Iron in chromic acid is also separated as the hydrous oxide, then dissolved in HCl, reduced to Fe(II) with hydroxylamine hydrochloride, complexed with bathophenanthroline disulphonic acid and measured spectrophotometrically at 533 mmicro. Repetitive analyses of a sample of chromic acid showed 2-6 ppm of iron (s = 0.35, n = 8).     

On the detection of aluminium by means of aluminon

The well-known reaction of aluminium with aluminon has been modified in such a way as to make it specific for this element. This has been accomplished by adding sulphurous acid beforehand and ethanol and hydrochloric acid afterwards. Thc first reagent prevents the interference of chromium, indium, gallium, and titranium; the second those of beryllium, scandium, zirconium and small amounts of ferric iron.     

Determination of aluminium and chromium in serum by atomic absorption spectrometry

Summary The optimal conditions for the determination of aluminium and chromium in blood serum are proposed. Several sample pretreatment procedures for the purpose are compared. The best results are obtained by sample dilution with nitric acid (0.1 mol/l) and addition of Mg(NO₃)₂ as modifier with a magnesium concentration of 0.2 mg/ml. This procedure has been used for studying the intestinal intake of aluminium by patients after oral administration of aluminium compounds.     

Solid-state mechanochemical synthesis of cobalt(III), iron(III), and chromium(III) bisdicarbollyl complexes

Thallous dicarbollide reacts with cobalt(II), iron(III) and chromium(III) chlorides without a solvent under conditions of mechanical activation to form the corresponding carborane complexes of tervalent metals. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1715–1717, October, 1993.     

Rapid chelatometric estimation of chromium, iron and aluminium in chromium + iron and chromium + aluminium mixtures

Summary A study of the kinetics of the reaction of chromium(III) with EDTA [1,2] had shown that the rate of reaction, usually slow, can be accelerated in the presence of hydrogen carbonate, sulphite, nitrite and organic solvents like alcohols, ketone, dioxane, etc., or suppressed in the presence of oxalate, acetate, etc. Based on this principle, a rapid titrimetric method using EDTA was developed for the estimation of chromium(III), iron and aluminium in chromium(III) + iron and chromium(III) + aluminium mixtures. The method has been extended for the estimation of iron and chromium(III) in stainless steel. Results are satisfactory.

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Zusammenfassung Die Reaktion von Chrom(III) mit äDTA kann durch Hydrogencarbonat Sulfit, Nitrit sowie organische Lösungsmittel beschleunigt oder durch Oxalat, Acetat u. a. unterdrückt werden. Aufgrund dieser Erscheinung wurde ein chelatometrisches Verfahren zur Bestimmung von Chrom(III), Eisen und Aluminium in Gemischen von Cr + Fe oder Cr + Al ausgearbeitet, das auch auf die Bestimmung von Eisen und Chrom in rostfreiem Stahl angewendet wurde. Es wurden befriedigende Ergebnisse erhalten.

     

The application of differential pulse polarography to the determination of a pharmacologically active benzhydrylpiperazine derivative and its major electroactive metabolites in the plasma and urine of animals.

A method for the determination of 1–500 p.p.m. of acid-soluble aluminium and 2–500 p.p.m. of acid-insoluble aluminium in low-alloy and stainless steels by flameless atomic absorption with a HGA 74 graphite furnace is described. A typical value of the relative standard deviation for acid-soluble aluminium at concentrations larger than 10 p.p.m. was 5 %. The steel sample was dissolved in hydrochloric and nitric acid and filtered. Ammonium sulphate was added to the filtered sample in order to overcome interferences caused by hydrochloric acid. No concentration steps were used. Acid-soluble aluminium was determined within 20 min. The influence of iron, chromium, nickel, molybdenum, hydrochloric acid, nitric acid and ammonium sulphate respectively was investigated.     

Metallochlorophosphates-Perspective Binders for Heat Resistive Compositions

Abstract

New ways of synthesizing aluminium, magnesium and chromium phosphate binders with phosphorous metal ratio of 1:l were discovered. It was found that the viscous solution of met-allochlorophosphate binders and powdered chlorophosphate aluminium, magnesium and chromium can be used as a component for heat resistive materials. Viscous binders increase the mechanical strength, while powdered chlorophosphates ensure safe storage, usage and transportation. Investigation of formation conditions, constituent, pnysico-chemical properties and thermal treatment of liquid binders and precipitated from it aluminium, chromium and magnesium chlorophosphate showed the presence of MHPO₄ · nH₂O where M-Al, Cr and MgH₂PO₄Cl·nH₂O where n = 2–6. It was found that similar compounds are formed by the reaction of metallic chloride with phosphoric acid and metallic hydrooxide, the mixture of phosphoric and hydrochloric acids having M:P:Cl = 1:1:1.1–1.8 ratio. The latter method is more technological. It was stated that the viscosity, density and stability of liquid chlorophosphate binders depend on the nature of cations: viscosity increases, while density decreases from Cr-Mg-Al, precrystallization period increases from 1 to 3 days for magnesium up to 3–5 months for aluminium, and a year for chromium. As a result of thermal treatment metallic orthophosphate without water of crystallization is produced. Highly effective heat resistive materials with compressive strength of 70–106 MPa, refrectoriness 1300–1800°C oped. ?1800°C and hardening temperature of 150–350°C are developed.     

Atomization efficiencies in halocarbon-loaded acetylene-air flames—II. Formation of dihalides and combined effects on vaporization and gas phase atomization processes

Halocarbon vapours (CCl₄ and in some cases CF₂Cl₂) were introduced into an acetylene-air flame at increasing rates while nebulizing individual solutions of alkaline earth elements, iron, manganese, chromium, molybdenum, tin and also magnesium in the presence of aluminium matrix. Following the theory developed by Sugden and Bulewicz dealing with the signal depression caused by the presence of halocarbons, the formation of dichloride species for the alkaline earth metals and also for iron, manganese and chromium could be elucidated. From the anomalous shapes of the Sugden-Bulewicz plots, incomplete solute vaporization is inferred for magnesium in the presence of aluminium. For the latter binary system, an almost complete evaporation of magnesium could be attained at 1.2% volume concentration of CCl₄ vapour in the flame.     

One-step synthesis of oxazolinoazetidinones from penicillin sulfoxides: potential intermediates for 1-oxacephem synthesis

Reaction of penicillin sulfoxides with a tervalent phosphorous compound in the presence of a catalytic amount of squaric acid gave oxazolinoazetidinones, potential intermediates for synthesis of 1-oxacephems, in good yields.2β-Chloromethyl- and 6α-methoxypenicillin sulfoxides also undergo this reaction. The reaction contrasts with the well-known Cooper reaction which usually gives thiazolinoazetidinones.     

Slurry-electrothermal atomic absorption spectrometric determination of aluminium and chromium in vegetables using hydrogen peroxide as a matrix modifier

Fast heating programmes for determining aluminium and chromium in vegetables using electrothermal atomic absorption spectrometry with slurry sampling are developed using wall atomization. The build-up of carbonaceous residues inside the atomizer is avoided by adding 4% hydrogen peroxide and 1% nitric acid to the slurries instead of using an air-ashing stage. In accordance with fast-programme methodology, the conventional drying and charring steps are replaced by a modified drying stage. simplifying the heating programmes. For suspensions containing 0.1% m/V of ground vegetables, the relative standard deviation (RSD) is about +/-5% for aluminium. For chromium determination, the use of 0.5-1% m/V suspensions leads to RSDs close to +/-4%. Calibration is carried out using aqueous standards. The aluminium and chromium contents of a number of vegetable samples obtained by using the slurry approach agree with those obtained by means of a conventional procedure based on the total dissolution of the samples. The reliability of the procedures is also confirmed by analysing two certified reference materials.     

The determination of chromium in water samples by neutron activation analysis after preconcentration on activated carbon

A method is presented for the determination of chromium in sea-and fresh water. Chromium is concentrated on activated carbon from neutral solution after a previous reduction of chromate with sodium sulfite at pH 1.5. The final determination of the total chromium content is performed by instrumental neutron activation analysis. By preconcentration on activated carbon a differentiation between tervalent and hexavalent chromium is possible. A separate determination of both species is not yet feasible due to the high carbon blank and to the necessity of measuring the adsorption percentage on carbon. The lower limit of determination, which depends on the value of the carbon blank, is 0.05 μg Cr·1⁻¹ with a precision of 20%.     

Studies on a vapour-phase process for the manufacture of chlorofluoroethanes

Fluorination of hexachloroethane or of tetrachloroethylene + chlorine by hydrogen fluoride at ca. 400°C in the presence of an aluminium fluoride catalyst gives the unsymmetrical isomers of dichlorotetrafluoroethane and of trichlorotrifluoroethane as the major products. Under similar conditions but using a catalyst of aluminium fluoride containing small amounts of iron, chromium and nickel, symmetrical trichlorotrifluoroethane is the major product. Analogous fluorinations of various intermediates over these catalyst systems have been studied and detailed information about the reaction pathways obtained. Under suitable conditions, s-trichlorotrifluoroethane or s-dichlorotetrafluoroethane can be prepared in a high state of purity.     

A radioanalytical study of the chromate conversion coating formed on aluminium

Phosphate/chromate and accelerated chromate coatings were produced on commercially available aluminium. The Cr, P and Fe components of the conversion coatings were determined by radioactive tracer technique. The tracer technique was combined with ion-exchange and film-sectioning methods to determine the chromium (III)/total chromium ratio in the accelerated chromate coating. It was found that during the acidic dissolution of the conversion coating the chromium (III)/total chromium ratio may suffer changes. The filmforming components in the metal/bath interface are supersaturated and deposited onto the aluminium. The identified components of the accelerated chromate coatings are Cr/OH/₃, Cr/OH/CrO₄ and Cr₄[Fe/CN/₆]₃ and the chromium (III)/total chromium ratio was found to be cca. 2/3.     

Extractive spectrophotometry of the molybdenum (III) 1,10-phenanthroline thiocyanate and 2,2'-bipyridyl thiocyanate complexes

New extraction spectrophotometric methods for the determination of small amounts of molybdenum have been developed, using thiocyanate and 1,10-phenanthroline or 2,2'-bipyridyl as reagents in the presence of chlorostannous acid. Extracts of the ternary complexes of tervalent molybdenum in 1,2-dichloroethane obey Beer's law in the range 1-10 mug/ml at 525 nm. A 10-fold excess of iron and vanadium and 100-fold excess of tungsten, phosphorus and silicate do not interfere.     

Voltammetric Determination of Aluminium in Haemodialysis Concentrates Using the Adsorption of the Al(III)-1,2-Dihydroxyantraquinone-3-sulphonic Acid Complex in Presence of Calcium

Abstract

This paper describes a method for the quantitative determination of aluminium in haemodialysis concentrates, based on the adsorption on a static mercury drop electrode of the Al-1,2 dihydroxyantraquinone-3-sulphonic acid complex. The signal was notably increased in presence of calcium. The electrolysis was carried out at -0.900 V. After 60 sec the aluminium contents were measured by differential pulse voltammetry. In these conditions aluminium can be determined in the range 0.65–38 ng/ml with a detection limit (3[sgrave]) of 0.20 ng/ml. The relative standard deviation was in all instances less than 2.1%.     

Thermometrische Schnellanalyse von Martin- und Hochofenschlacken sowie anderen Silicaten

Summary A novel method has been developed for the rapid analysis of silicates. Each component is determined from the temperature variation of the solution resulting from the addition to the test solution of a selectively reacting reagent. By suitable construction of the instrument the concentration of the component to be determined can be read directly in per cent. The determination of a component takes usually 4 to 8 minutes.In the test solution a temperature change proportional to the concentration of the component to be determined has been produced by the following reagents: sulphuric acid for barium, ammonium peroxodisulphate for iron, hydrogen peroxide for titanium, hydrofluoric acid for silicic acid, potassium permanganate for sulphur, ammonium molybdate and hydrogen peroxide for phosphate, potassium permanganate for manganese, potassium oxalate for calcium, diammonium hydrogenphosphate for magnesium, ascorbic acid for chromium. The above components can be determined without any separations. Only in the case of aluminium a separation of silicic acid from aluminium by dehydrating with perchloric acid in necessary. Thereafter the aluminium can be determined with hydrofluoric acid.The precision of the determinations is practically identical with the precision of the usual plant methods.