Spectrophotometric determination of gallium(III) with carminic acid and hexadecylpyridinium chloride

A Spectrophotometric method is proposed for determining dipyridamole in pure form and in pharmaceutical preparations. Chromotrope 2B was used as a charge-transfer complex forming agent with absorption maximum 40 nm red shifted relative to the chromotrope 2B itself. The variables affecting the formation of the C.T. complex were studied and optimized. Linear calibration graphs were obtained up to 60 g ml^–1 at room temperature. The method was found to be accurate, precise and can be successfully used for authentic and pharmaceutical preparations in the working range up to 600 g.A conductimetric method using phosphotungstic acid as ion-associate forming agent is proposed. The relative average error is 1–2%. Water-ethanol (12) mixture was used as solvent. Excellent recoveries and low standard deviations were obtained. Working ranges are 40–260 mg and 35–110 mg for pure dipyridamole and tablets, respectively.On leave from Department of Chemistry, Faculty of Science, Allepo University, Allepo, Syria     

Spectrophotometric determination of beryllium with calcichrome

A method is established for the spectrophotometric determination of small amounts of beryllium as a 1:1 complex with Calcichrome in slightly acidic solution. Beer's law is obeyed over the range 0.05-0.6 ppm Be in the final solution and the apparent molar absorptivity is 9.7 x 10(3) l.mole(-1). cm(-1) at 625 nm. Up to about 15 mug of beryllium in the final solution can be sensitively and selectively determined with a relative error of less than 2% in the presence of EDTA as masking agent.     

Spectrophotometric determination of beryllium

Summary A spectrophotometric method for determination of beryllium ing quantities is described which is based on color reaction between beryllium and rufigallol having maximum absorption at 530 nm. Comparing various solvents, the suitable medium found is DMSO-H₂O (3 2). Interference of Al, Zr, Th, Hf and many other cations have been removed by solvent extraction of their oxinates with chloroform.

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Zusammenfassung Eine spektrophotometrische Bestimmungsmethode für Mikrogrammmengen Be wurde beschrieben, die auf der Farbreaktion mit Rufigallol mit einem Absorptionsmaximum bei 530 nm beruht. Als geeignetes Medium erwies sich Dimethylsulfoxid in Wasser (3 2). Störende Kationen wie Al, Zr, Th, Hf und viele andere werden in Form ihrer Oxinate mit Chloroform extrahiert.

     

Spectrophotometric determination of beryllium with chromotropic acid azo dyes of the pyridine series

Summary Beryllium forms coloured complexes with azo dyes of the pyridine series e. g. 2-(pyridyl-2-azo)-chromotropic acid (A), 2-(pyridyl-3-azo)-chromotropic acid (B) and 2-(2-carboxy pyridyl-3-azo)-chromotropic acid (C). The latter two reagents react with aluminium also, but beryllium can be estimated in the presence of large excess of aluminium only with A.At pH 6.5, the colour systems formed show maximum absorptions at 580 nm with A and at 590 nm with B and C and obey Beer's law with optimum ranges of beryllium from 0.5 to 2.0 ppm with A, from 0.2 to 0.8 ppm with B and 0.3 to 2.0 ppm with C. The metal forms a 1:3 complex with A, a 12 complex with B and a 32 complex with C, with instability constants of the order of 10^–13, 10^–9 and 10^–17, respectively.

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Zusammenfassung Im Hinblick auf die spektrophotometrische Berylliumbestimmung wurden drei verschiedene Farbkomplexe untersucht, die Be mit Azofarbstoffen der Pyridinreihe bildet, nämlich mit 2-(Pyridyl-2-azo)-chromotropsäure (A), 2-(Pyridyl-3-azo)-chromotropsäure (B) und 2-(2-Carboxy-pyridyl-3-azo)-chromotropsäure (C). B und C reagieren auch mit Aluminium, jedoch kann Beryllium neben großen Mengen Al mit Reagens A bestimmt werden. Bei pH 6,5 liegen die Absorptionsmaxima bei 580 nm (A) bzw. 590 nm (B, C). Das Beersche Gesetz wird von 0,5 bis 2,0 ppm (A) bzw. 0,2–0,8 ppm (B) bzw. 0,3–2,0 ppm (C) befolgt. Die Zusammensetzung des Komplexes (Be: Reagens) beträgt 13, 12 bzw. 32; die Instabilitätskonstanten sind in der Größenordnung 10^–13, 10^–9 bzw. 10^–17 (für A, B, C).

     

Spectrophotometric determination of boron in cobalt and nickel coatings by means of carminic acid

A method is proposed for the determination of boron in cobalt and nickel coatings deposited from borane-type baths. The deposit is dissolved in hydrochloric acid in the presence of platinum chloride as catalyst, potassium chloride and mannitol are added, and the solution is evaporated to dryness. Boron is then distilled as methyl borate into sodium hydroxide solution, the distillate is evaporated to dryness, and the boron is determined spectrophotometrically with carminic acid. The mannoitol prevents volatilization of boron during the evaporation. Evaporating the hydrochloric acid solution to dryness eliminates excess of acid and water, both of which cause incomplete recovery of boron in the distillation. The potassium, cobalt, and nickel chlorides left after the evaporation dissolve in the hot methanol during the distillation and do not interfere.     

Spectrophotometric determination of beryllium in bronzes with Chrome Azurol S

Summary Spectrophotometric Determination of Beryllium in Bronzes with Chrome Azttrol S Some remarks on the spectrophotometric determination of beryllium in bronzes using Chrome Azurol S (CAS) are given. The determination was performed at pH=6.5 and 10.0 using hexamethylene-tetramine and ammoniacal buffers, respectively. It was demonstrated that the determination of Be with CAS at pH=10.0 is slightly less sensitive, but it has two advantages which are important in obtaining reliable results. First, is the shorter time to reach the equilibrium between Be and CAS, and second, is lower pH sensitivity so that a better precision of the results at pH=10.0 overcompensate the slightly lower sensitivity at this pH in comparison with that at pH=6.5.     

Spectrophotometric determination of beryllium in air and dust

The requirements of beryllium monitoring are discussed. Emphasis is placed on developing an Analytical procedure which is rapid, simple to operate, of adequate sensitivity and of reasonable accuracy. For air analysis, beryllium bearing dust is collected on a membrane filter, the beryllium is obtained in solution and determined spectrophotometrically, using aurine tricarboxylic acid (aluminon) as reagent Interference due to other metals is avoided by the addition of suitable complexing agents. A sensitivity of 0 1 μg Be can be achieved     

Spectrophotometric determination of nitrite based on its catalytic effect on the oxidation of carminic acid by bromate

A highly sensitive and selective method is described for the determination of trace amounts of nitrite based on its effect on the oxidation of carminic acid with bromate. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 490 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1.8×10⁻¹ mol l⁻¹ H₂SO₄, 3.8×10⁻³ mol l⁻¹ KBrO₃, and 1.2×10⁻⁴ mol l⁻¹ carminic acid at 30°C. By using the recommended procedure, the calibration graph was linear from 0.2 to 14 ng ml⁻¹ of nitrite; the detection limit was 0.04 ng ml⁻¹; the R.S.D. for six replicate determinations of 6 ng ml⁻¹ was 1.7%. The method is mostly free from interference, especially from large amounts of nitrate and ammonium ions. The proposed method was applied to the determination of nitrite in rain and river water.     

Spectrophotometric determination of osmium based on its catalytic effect on the oxidation of carminic acid by hydrogen peroxide

A highly sensitive spectrophotometric method is described for the determination of trace amounts of osmium(VIII), based on its catalytic effect on the oxidation of carminic acid by hydrogen peroxide. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of carminic acid at 540 nm after 3 min of mixing the reagents. The optimum reaction conditions were 1x10(-4) mol l(-1) carminic acid, 0.013 mol l(-1) hydrogen peroxide and pH 10 at 25 degrees C. By using the recommended procedure, the calibration graph was linear from 0.1 to 1.5 ng ml(-1) of osmium; the detection limit was 0.02 ng ml(-1); the RSD for five replicate determinations of 0.2-1.4 ng ml(-1) was in the range of 1.8-4.7%. The influence of several foreign ions on osmium determination were studied and the effect of interfering ions were removed by extracting osmium into isobuthyl methyl ketone and back extracting into sodium hydroxide solution.     

Spectrophotometric determination of trace amounts of beryllium in silicate materials

Although photometric determination of beryllium is generally quite satisfactory in trace analysis, application to geochemical samples is restricted because of the numerous interfering ions. Introduction of an extraction procedure eliminates the interference of Al and Fe, which occur in high concentrations in most silicate rocks, and enables beryllium to be determined with Eriochrome Cyanine R. Use of the method for analysis of six international geochemical reference samples containing between 1 and 30 ppm beryllium has given satisfactory results (relative standard deviation from 1.6 to 7.8%).     

Spectrophotometric molybdenum determination with thiolactic acid

A quick, selective method for molybdenum(VI) is based on the formation of a yellow thiolactic acid complex. The complex is formed at pH 1.0-1.6, and the absorbance is measured at 365 nm.     

Spectrophotometric determination of beryllium and zirconium using chromotrope-2C

Summary Disodium salt of o-carboxyphenylazo chromotropic acid (chromotrope 2C) has been used for the colorimetric determination of microamounts of beryllium and zirconium. The red-violet complexes show maximum absorption at 580 nm and the colour systems obey Beer's law from 0.025 to 0.375 ppm of beryllium and 2 to 12 ppm of zirconium. The optimum concentration ranges are from 0.125 to 0.375 ppm for beryllium and from 4 to 12 ppm for zirconium, where the percent relative errors per 1% absolute photometric error are, respectively, 3.014 and 3.22. The sensitivity of the reactions per cm² are 0.00067 g Be and 0.027 g Zr. The complexes, with the metal to reagent ratio of 11, have instability constants as 2.836 · 10^–6 for beryllium and 6.026 · 10^–6 for zirconium.     

Spectrophotometric determination of cerium with sulphanilic acid

In the presence of other rare earths, cerium(IV) can be determined spectrophotometrically by its reaction with sulphanilic acid with which it produces a red colour. Solutions containing 28-210 ppm of cerium absorb at 495 mmicro according to Beer's law. Other rare earths, except neodymium, and many common ions do not interfere. Strong oxidising agents and neodymium in greater than fifty times the concentration of cerium interfere with this method. The precision depends on the control of pH and time. Cerium alloys have been analysed by this method and the results are compared with those obtained by another spectrophotometric method.     

Spectrophotometric determination of bismuth with diethylenetriaminepenta-acetic acid

Diethylenetriaminepenta-acetic acid is used for spectrophotometric determination of bismuth (at 270 nm) in 1.6 M perchloric acid. The system obeys Beer's law in the range 1–40 μg/ml. The method has been tested for the determination of bismuth in pure lead and polymetallic ores.     

Spectrophotometric determination of cobalt with gluconic acid

Summary A new spectrophotometric method is proposed for determining cobalt using gluconic acid as a chromogenic reagent. The parameters fundamentally affecting the absorbance of the complex are studied and obeyance of Beer's law between 5.33 and 53.3 g of Co²⁺/ml has been found. Measurements have to be carried out at 330 nm. The complex is formed in the molar ratio 11.

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Spektralphotometrische Bestimmung von Kobalt mit Hilfe von Gluconsäure

Zusammenfassung Die vorgeschlagene Methode verwendet Gluconsäure als farbbildendes Reagens. Untersucht wird der Einfluß verschiedener Parameter auf die Absorption des Kobalt(II)-Gluconsäure-Komplexes. Das Beersche Gesetz gilt im Bereich von 5,33–53,3 g Co²⁺/ml. Die Messung der Absorption erfolgt bei 330 nm. Das Molverhältnis des Komplexes beträgt 11.

     

Spectrophotometric determination of cobalt with nitrosochromotropic acid

A sensitive spectrophotometric method for the determination of trace amounts of cobalt based on the complex formation with nitrosochromotropic acid in ammoniacal medium is described. After its extraction as thiocyanate complex into isobutylmethyl ketone, cobalt is stripped into nitrosochromotropic acid in ammonia buffer. The method has been applied to the determination of cobalt in mild steel, ferrous alloys and multivitamin preparations.     

Spectrophotometric determination of yttrium with molybdophosphoric acid

A simple sensitive spectrophotometric determination of yttrium, based on the reaction of molybdophosphoric acid with yttrium at pH 4.8, is described. The resulting complex is reduced and the absorbance measured at 695 nm. The method is applicable in the presence of several-fold excesses of lanthanum, cerium, and phosphate.