Determination Of Cobalt In Alloys Research Articles

Derivative Spectrophotometric Determination of Cobalt in Alloys and Biological Samples after Preconcentration with the Ion Pair of Disodium 1-Nitroso-2-naphthol-3,6-disulfonate and Tetradecyldimethylbenzylammonium Chloride on Microcrystalline Naphthalene or Column Method

Cobalt was quantitatively retained by disodium 1-nitroso-2-naphthol-3,6-disulfonate (nitroso-R salt) and tetradecyldimethylbenzylammonium chloride (TDBA+Cl-) on microcrystalline naphthalene in the pH range 3.6 - 8.2 from large volumes of aqueous solutions of various alloys and biological samples. After filtration, a solid mass consisting of the cobalt complex and naphthalene was dissolved with 5 ml of dimethylformamide (DMF), and the metal was determined by third-derivative spectrophotometry. The cobalt complex could alternatively be quantitatively adsorbed on tetradecyldimethylbenzylammonium-naphthalene adsorbent packed in a column and determined similarly. The detection limit was 30 ppb (signal to noise ratio = 2) and the calibration curve was linear for 0.1 - 11 ppm in dimethylformamide solution with a correlation coefficient of 0.9996 by measuring the distance, d3A/d λ3, between λ1 (612 nm) and λ2 (579 nm). Eight replicated determinations of 2 ppm of cobalt in dimethylformamide solution gave a mean intensity (peak to peak signal between λ1 and λ2) of 0.436 with a relative standard deviation of ±0.91%. The sensitivity of the method was 0.215 (d3A/dnm3) ml/µg, which was found from the slope of the calibration curve. Various parameters, such as the effect of the pH, the volume of the aqueous phase and the interference of a number of metal ions on the determination of cobalt has been studied in detail to optimize the conditions for the determination cobalt in various alloys and biological samples.

Spectrophotometric determination of cobalt in iron-, cobalt- and nickel-base alloys

A spectrophotometric method has been developed for the accurate determination of cobalt at milligram level, based on oxidation of the cobalt(II)—EDTA complex with gold(III) chloride at pH 4.0–6.5 and 100° and measurement of the absorbance of the resultant violet cobalt(III)—EDTA complex at 535 nm. The precision is not affected by the presence of several metal ions; including coloured ones such as Cu(II), Ni(II) and Fe(III). However, chromium(III) interferes since it also forms a violet complex with EDTA, but can be removed by separation with pyridine. Practical application of the method is illustrated by the determination of cobalt in alloys based on iron, cobalt and nickel. Over the cobalt range 8–52% the error ranges from 0.1 to 0.3%.

Direct spectrophotometric method for the determination of cobalt with indane 1,2,3-trionetrioxime in aqueous medium

A simple, sensitive and selective Spectrophotometric method has been developed for the determination of cobalt using indane 1,2,3-trionetrioxime (ITT): The method is based on the colour reaction between ITT and cobalt(II) in sodium acetate-acetic acid buffer (pH 4.5–7.5) medium. The calibration graph for measurement at 320 nm is linear in the range 1.18–23.60μg of cobalt per 25 ml, with molar absorptivity of 5.32×1041mol−1 cm−1. The effect of interfering ions has been studied and the method was applied to the determination of cobalt in alloys, with good results.

Spectrophotometric determination of cobalt with cyclohexane-1, 2-dione bis(2-pyridylhydrazone)

A method for the spectrophotometric determination of cobalt with cyclohexane-1,2-dione bis(2-pyridylhydrazone) is described. The pink complex is formed at an initial pH of 4–5 in a medium containing 12%V/V dimethylformamide, and the absorbance is measured at 525 nm at a final perchloric acid concentration of ca. 0.5 M. The molar absorbtivity is 13700 l mol–1 cm–1. The method has been applied to the determination of cobalt in alloys and minerals.

Dosage potentiométrique du cobalt après séparation sur résines échangeuses d'ions: Applications à l'analyse des aciers et alliages

The main methods for the determination of cobalt in alloys and steels are briefly reviewed. An electrochemical method based on the oxidation of cobalt-ammine complexes by hexacyanoferrate(III) is applied. The various factors which could affect the measurements are examined, particularly pH and interferences. Iron, vanadium, manganese, molybdenum, tungsten, etc. are separated on a cationic resin in a hydrofluoric acid medium. Cobalt is further separated from manganese and chromium on an anionic resin from which it is eluted with hydrochloric acid. A procedure suitable for application to alloys and steels containing 4–80% cobalt is described.