Determination of vanadium and molybdenum by atomic-absorption spectrophotometry

A method is described for the determination by atomic-absorption spectrophotometry of vanadium and molybdenum, up to the milligram level, in samples of yellow cake, uranium-bearing minerals and geochemical standards. After attack with acids these two elements are separated from each other and from matrix elements by means of anion-exchange in 6M hydrochloric acid on the strongly basic anion-exchange resin Dowex 1, X8 (chloride form). Vanadium is unadsorbed and passes into the effluent while molybdenum is adsorbed on the resin. For the elution of molybdenum a mixed aqueous-organic solvent system consisting of methanol and 6M hydrochloric acid (9: 1 v/v) is used. After evaporation of the 6M hydrochloric acid effluent and of the mixed aqueous-organic eluate vanadium and molybdenum are determined by atomic-absorption spectrophotometry. The method was tested by analysing numerous samples with contents ranging from a few ppm to milligram amounts of vanadium and molybdenum. For comparison, the concentrations of these two elements were determined in a large number of samples by spectrophotometric and titrimetric procedures. In all cases very good agreement of results was obtained.     

Determination of mercury by atomic-absorption spectrophotometry

A flameless atomic-absorption system has been developed for the determination of low concentrations of mercury in gaseous, solid and liquid samples of organic and inorganic materials.     

Determination of copper and molybdenum in the hard dental tissues of rats by atomic-absorption spectrophotometry

The measurement of uptake of copper and molybdenum from the diet into rat's teeth required the use of an accurate but rapid method of analysis. The simultaneous extraction of copper and molybdenum with APDC from the sample, combined with atomic absorption, proved to be both accurate and reliable. Interference from other elements present in the sample was easily overcome by the use of standards with a matrix equivalent to that of the teeth.     

Determination of cadmium by atomic-fluorescence and atomic-absorption spectrophotometry

The adaptation of a conventional atomic-absorption/flameemission spectrophotometer to the measurement of atomic-fluorescence in an air-acetylene flame is described. The determination of cadmium on the same instrument by both atomic-fluorescence and absorption shows that, even with a rather simple and inefficient means of exciting and measuring fluorescence, results can be obtained which indicate that the fluorescence technique is considerably more sensitive than atomic-absorbance and is equally free from inter-element interference.     

Determination of metals in phospholipids by atomic-absorption spectrophotometry

A procedure is described for the determination of sodium, potassium, calcium, magnesium and manganese in phospholipids by atomic-absorption spectrophotometry. The method uses a solution of phospholipid in isopentyl acetate; phosphate interference is controlled by the addition of aqueous lanthanum chloride solution homogenized with ethanol. Standards are prepared in a similar solvent mixture. A comparison between the described method and that of standard additions show it to be free of phospholipid matrix effects.     

Determination of lead in propellant samples by atomic-absorption spectrophotometry

A procedure is described for the determination of lead in different types of propellant samples by atomic-absorption spectrophotometry. The method is simple, rapid and avoids the use of strong acids and prior sample digestion. Complete lead extraction is achieved with 10% acetic acid. The results obtained by the proposed method are compared with those obtained by the gravimetric chromate method. The variation of the efficiency of lead extraction with sample type is discussed.     

Determination of vanadium in ore samples by atomic-absorption spectrophotometry

An atomic-absorption method is described for the determination of vanadium in ores. With a nitrous oxide-acetylene flame and 200 ppm of Al(3+) added to the sample, a sensitivity of 0.2 ppm for 1% absorption can be obtained. Iron above 0.015M interferes but can be extracted into isopropyl ether from 8M hydrochloric acid; the hydrochloric add itself then interferes and must be removed by evaporation.     

Determination of chromium in low-alloy steels by atomic-absorption spectrophotometry

Iron causes severe depression of the signal in determination of chromium by atomic-absorption spectrophotometry in an air-acetylene flame. This effect can be eliminated by addition of hydroxylamine hydrochloride and use of a fuel-rich flame. Addition of iron to the standard solutions is not necessary for up to 300 ppm of iron in the test solution.     

Determination of arsenic in high-purity copper by flameless atomic-absorption spectrophotometry

Arsenic is separated from an ammoniacal solution containing 1 g or less of copper(II) by co-precipitation with ferric hydroxide. The precipitate is dissolved in nitric acid, the solution almost neutralized with ammonia, made up to volume and the As determined by flameless atomic-absorption spectrophotometry. Less than 0.5 ppm can be determined.     

Determination of trace quantities of selenium by indirect atomic-absorption spectrophotometry

The selenium(IV)-iodide interaction in acid medium, leading to the liberation of iodine, has been utilized for the indirect determination of selenium by atomic-absorption spectrophotometry (AAS). The iodine is extracted into benzene and subsequently reductively stripped into an aqueous solution of ascorbic acid. After extraction of the resulting iodide as tris(1,10-phenanthroline)cadmium(II) iodide into nitrobenzene, the cadmium content of the organic extract is determined by AAS. Beer's law is applicable up to 0.75 ppm of selenium. The few interferences are readily overcome. The chemical yield in the system is about 80% overall.     

Determination of molybdenum in ores, iron and steel by atomic-absorption spectrophotometry after separation by alpha-benzoinoxime extraction or further xanthate extraction

A simple and moderately rapid method for determining 0.001% or more of molybdenum in ores, iron and steel is described. After sample decomposition, molybdenum is separated from the matrix elements, except tungsten, by chloroform extraction of its alpha-benzoinoxime complex from a 1.75 M hydrochloric-0.13 M tartaric acid medium. Depending on the amount of tungsten present, molybdenum, if necessary, is back-extracted into concentrated ammonia solution and subsequently separated from coextracted tungsten by chloroform extraction of its xanthate complex from a 1.5M hydrochloric-0.13M tartaric acid medium. It is ultimately determined by atomic-absorption spectrophotometry, at 313.3 nm, in a 15% v/v hydrochloric acid medium containing 1,000 microg/ml of aluminium as the chloride, after evaporation of either extract to dryness with nitric, perchloric and sulphuric acids and dissolution of the salts in dilute ammonia solution.     

Analytical application of emulsions Determination of lead in gasoline by atomic-absorption spectrophotometry

A simple rapid method of determining lead in gasoline by AAS with use of stable emulsions has been developed. The emulsions were stabilized with propan-2-ol or a mixture of ethanol and a surface-active agent. The results obtained showed good reproducibility and accuracy and the method is suitable for routine analysis.     

Determination of niobium in rocks, ores and alloys by atomic-absorption spectrophotometry

Niobium, in concentrations as low as 0.02% Nb(2)O(5), is determined in a variety of materials without separation or enrichment. Chemical and ionization interferences are controlled, and sensitivity is increased, by maintaining the iron, aluminium, hydrofluoric acid and potassium content within certain broad concentration limits. There is close agreement with the results of analyses by emission spectrographic, electron microprobe and X-ray fluorescence methods.     

Determination of tin and triorganotin compounds in sea-water by graphite-furnace atomic-absorption spectrophotometry

An analytical method based on graphite-furnace atomic-absorption spectrophotometry employing a suitable signal-enhancing medium for determination of inorganic tin and two of its trisubstituted organic derivatives in sea-water has been established. This method allows determination of triphenyltin and tributyltin compounds down to 2 x 10(-12) and 2.8 x 10(-12)M respectively by means of enrichment by collection on graphitized carbon black (enrichment factor up to 8 x 10(4)) and a separation on a small silica-gel column. Inorganic tin, which is not adsorbed on the graphitized carbon black, is isolated from the matrix by liquid-liquid extraction of its pyrrolidinedithiocarbamate complex into dichloromethane. The method gives good recovery (95%) and precision ( less, similar5%) at the ng/l. level.     

Determination of lead in tooth-pastes by electrothermal atomic-absorption spectrophotometry with platform atomization

Electrothermal atomic-absorption spectrometry is used for the determination of lead in tooth-pastes, by means of the graphite platform/matrix-modification technique. The method is easy to apply, has limited interferences and is more precise than conventional flame AAS. The working concentration range is up to 100 mug/1. The method is characterized by a detection limit of 0.08 mug/1. and a precision of +/-1.9 % for the sample solutions. For the tooth-pastes, the detection limit is between 1.1 and 5.4 ng/g and the precision in the range 1.8-10%.     

Determination of copper in ammonium fluoride solutions by extraction and atomic-absorption spectrophotometry

Extraction with sodium diethyldithiocarbamate, followed by mineralization and atomic-absorption spectroscopy is used to determine down to 10(-7)% Cu in 40% ammonium fluoride solution used in the manufacture of semiconductors.     

Indirect determination of iodate by atomic-absorption spectrophotometry

An indirect method for determination of trace iodate in certain high-purity chemicals by atomic-absorption spectrophotometry (AAS) is described. Iodate forms a stable ion-association complex [Hg(dipy)(2)](IO(3))(2) in neutral medium, which can be extracted into methyl isobutyl ketone with 99% efficiency. The extract can be analysed for mercury (and hence indirectly for iodate) by flameless AAS. The limit of detection for iodate by this method is 7.5 ng. Apparent recoveries of 92-112% have been obtained for spikes of 0.25-0.70 mug of iodate.     

Indirect determination of organic compounds by atomic-absorption spectrophotometry

A review of the published methods for analysis of organic compounds by atomic-absorption spectrophotometry is given. Most of the applications are based on precipitation of metal compounds or solvent extraction of metal chelates or ion-association complexes. Although many of the methods offer great sensitivity, simplicity, and speed of analysis, few have been widely accepted by analysts, but some have proved to be satisfactory in field trials.