Direct flame atomic-absorption determination of minor elements in argillites

The possibility of direct atomic-absorption determination of minor elements in argillites without preliminary concentration and separation is studied. The possibility is examined of producing an analytical flame zone in which free analyte atoms can be produced by use of chemical additives, such as potassium thiocyanate for molybdenum, and potassium thiocyanate plus dodecylamine hydrochloride for vanadium.     

Masking of iron with fluoride in the extractive atomic-absorption spectrometric determination of chromium in steel

Chromium in steel is determined by oxidation to dichromate, extraction into methyl isobutyl ketone from 1-3 M hydrochloric acid, and atomic-absorption measurements on the extract. The interference of iron in the atomic absorption is eliminated by using fluoride to keep the iron(III) in the aqueous phase in the extraction step.     

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.     

Use of complexing ligands in the determination of antimony and tin by atomic-absorption spectrometry

The atomic-absorption spectrophotometric determination of antimony is best achieved in the presence of either an ammonium fluoride, hydrochloric acid, nitric acid mixture, or one of the following complexing agents: tartaric acid, citric acid, oxalic acid, 2-mercaptopropanoic acid. The interference of the 29 metals tested is least in the ammonium fluoride-hydrochloric acid-nitric acid mixture and is similar in tartaric acid, citric acid and 2-mercaptopropanoic acid media. However, the interference is pronounced in oxalic acid. Tin can be determined if any of the complexing agents or 6M hydrochloric acid is present.     

Electrothermal atomic-absorption determination of vanadium

Factors such as sample nature, matrix and heating programme have been found to influence both the sensitivity and precision of the determination of vanadium by electrothermal AAS. The reciprocal sensitivity, detection limit and precision (RSD) are 55 pg, 86 pg and 4%, respectively for aqueous solutions and 88 pg, 80 pg and 4% for organic solutions. Only tungsten and nitric acid have been found to interfere appreciably. Moderately concentrated sodium chloride solutions (6%) can be analysed for vanadium (0.05 mug/ml) without background correction, as can the acid digests of phosphate rocks and crude petroleum samples.     

Electrothermal atomic-absorption spectrophotometric determination of molybdenum

The sensitivity for determining Mo by ETA-AA is dependent on the heating programme employed when the peak-height method is used, but not when the peak area is used for evaluation of the AA signals. The linear range is greater at lower heating rate. Molybdenum can be directly determined in up to 8% NaCl solution without chemical pretreatment or background correction by making use of the high ashing temperature allowed, at which the matrix NaCl can be totally removed. The minimum recovery is 94.5%. Amounts of alkaline earth metals greater than 4000 times the amount of Mo give scatter signals, but these are time-resolved from the Mo signal. Any small effect on the peak height or area can be compensated for by background correction. The interference of tungsten is significant even at low concentrations (2-5 mug/ml) owing to the formation of stable compounds. Mo is determined in brines and acid digests of phosphate rocks after preconcentration and separation with the APDC-MIBK system, by ETA-AA of the organic extracts with or without mineralization.     

Interferences in the atomic-absorption: determination of silicon

The following substances have been investigated with regard to their interfering effect in the determination of silicon by AAS: HCl, HNO(3), H(2)SO(4), Na(+), K(+), Cs(+), A1(3+), Ni(2+), Mn(2+), Fe(3+), V(5+), Mg(2+), Cu(2+), Zn(2+) and Ti(4+). Some ternary systems with aluminium have been studied to examine the additive effects. Most of the interferents enhance the silicon absorption; only nickel and the acids exert depressive effects; the interference of copper and zinc is negligible.     

Use of a liquid ion-exchanger in the solvent extraction and atomic-absorption determination of trace copper in waters

Copper in the 10-100 ppM range has been determined by a solvent extraction and atomic-absorption procedure involving the use of the liquid ion-exchanger Amberlite LA 2 in thiocyanate form. The procedure is rapid and gives results of good precision, and uses stable reagents and standard instrumentation.     

Determination of chromium in steel by atomic-absorption spectrometry with an air-acetylene flame

A new atomic-absorption procedure is described for the determination of chromium, at levels up to 1%, in steel. The method involves the use of the air-acetylene flame and incorporates 8-hydroxyquinoline as a releasing agent to suppress metallic interferences. Chemical operations have been reduced to a minimum in order to provide a simple, rapid and accurate procedure.     

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.     

Rapid determination of antimony in steel by flameless atomic-absorption

A method for the determination of 1-30 ppm or more of Sb in steel by using flameless atomic absorption has been developed. The sample was dissolved in aqua regia and 10 mul were pipetted into the Massmann-type furnace. It was shown that interferences from HCl, HNO(3), Ni and Fe could be eliminated if oxygen was excluded and the heating rate was sufficiently high. Chromium was added to the samples and standards to compensate for its influence. Cu, Co, Mn, Ti and Sn did not interfere. An intercomparison with other laboratories showed that this method gives the same result as extraction with TOPO in MIBK. The time for a complete analysis including dissolution was 15 min.     

Indirect determination of cyanide in water by atomic-absorption spectrophotometry

An indirect method for determination of trace cyanide in water by atomic-absorption spectrophotometry is described. Cyanide forms a stable complex anion with Pd in alkaline solution. This complex anion can form an ion-association complex with tetra-alkylammonium ions which can be extracted into n-butyl alcohol with an efficiency higher than 90%. The extract can be analysed directly for palladium (and hence indirectly for cyanide) by flame atomic-absorption spectrophotometry. The detection limit for cyanide by this method is 0.1 mug ml in the n-butyl alcohol extract. Beer's law is obeyed for 0.13-9 mug of CN(-) per ml of n-butyl alcohol. Several foreign ions do not interfere.     

Determination of subnanogram amounts of chromium in different matrices by flameless atomic-absorption spectroscopy

A carbon rod flameless atomizer is used for the determination of Cr in water, sea-water, sugar, glycine and blood. The reported analytical curves show that the quantitative determination of Cr in these matrices is feasible in the ppM-ppm range. The influence of the most common anionic and cationic interferents is reported.     

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.     

Arsenic determination with graphite-cloth ribbon in graphite-furnace atomic-absorption spectrometry

The determination of arsenic by atomic-absorption spectrometry with use of a graphite-cloth ribbon placed inside various types of graphite tubes was investigated. It was found that the graphite-cloth ribbon greatly enhances the sensitivity for arsenic and reduces the interferences from various heavy metals, especially when it is placed inside a pyrolytic graphite tube and a nitric acid matrix is used. This is attributed to condensation of arsenic on the ribbon, owing to a temperature lag during the drying and ashing cycles, and to the formation of interlamellar compounds of arsenic with graphite.     

Flame and flameless atomic-absorption determination of tellurium in geological materials

The sample is digested with a solution of hydrobromic acid and bromine and the excess of bromine is expelled. After dilution of the solution to approximately 3 M in hydrobromic acid, ascorbic acid is added to reduce iron(III) before extraction of tellurium into methyl isobutyl ketone (MIBK). An oxidizing air-acetylene flame is used to determine tellurium in the 0.1–20 ppm range. For samples containing 4–200 ppb of tellurium, a carbon-rod atomizer is used after the MIBK extract has been washed with 0.5 M hydrobromic acid to remove the residual iron. The flame procedure is useful for rapid preliminary monitoring, and the flameless procedure can determine tellurium at very low concentrations.     

Indirect determination of trace phenol in water by atomic-absorption spectrophotometry

An indirect method for determination of trace phenol in water by atomic-absorption spectrophotometry (AAS) is described. The phenol is brominated in acidic solution with KBrO(3)-KBr solution at room temperature. The excess of bromine is reacted with KI and the I(2) produced is extracted into cyclohexane and then reduced back to I(-) with ascorbic acid. The I(-) is then complexed with Cd(2+) in sulphuric acid medium and the complex extracted into MIBK. The extract is analysed by flame AAS for Cd (and hence indirectly for phenol). The linear concentration range for determination of phenol is 6 x 10(-7)-0.9 x 10(-5)M in aqueous solution. Several foreign ions and organic substances do not interfere.     

Equilibrium effects in the determination of tantalum by atomic-absorption spectroscopy

The effect of solution variables on the efficiency of tantalum atom formation in hot flames is considered in terms of competing equilibria.