Water-soluble polymers for spectrophotometric and flow injection determination of cobalt with nitroso-R-salt

The water-soluble polymers poly(ethylenimine), quaternized poly(ethylenimine), and poly-4-vinyl-(N-benzyltrimethyl) ammonium chloride were found to be able to change the kinetics of the reaction of cobalt with nitroso-R-salt and the optical density of the cobalt complex formed. The optimum pH range for the complex formation was a wide range from 1 to 10 and at pH 2 the reaction developed instantly. The calibration graph was linear in the range 0.005-2 mug ml(-1). The effective molar absorptivity coefficient of the complex was equal to (2.8+/-0.08)10(3). A spectrophotometric determination method for cobalt with nitroso-R-salt in the presence of water-soluble polymers (before and after membrane preconcentration) and a colorimetric flow injection method were developed. For the flow injection-based spectrophotometric determination, the calibration graph was linear in the concentration range of 0-4.0 mug ml(-1) cobalt with a regression coefficient of 0.9992. The relative standard deviation (R.S.D.) for the determination of 1.0 mug ml(-1) cobalt was 0.9% (ten replicate injections), and at all concentration measured, the R.S.D. of the data was below 5.0%. The proposed FI procedure was applied to river water samples after membrane preconcentration of cobalt. The limit of detection was 4 ng ml(-1).     

Photometric, colorimetric, and acid-base characteristics of nitroso-R-salt

Optical and colorimetric characteristics of 1-nitroso-2-naphthol-3,6-disulfonic acid (nitroso-R-salt) are studied in aqueous solutions at pH 4–10. Equations of calibration plots are obtained as the colorimetric functions of the concentration, and the molar coefficients of the colorimetric functions are calculated. The dissociation constants of nitroso-R-salt are determined by colorimetry at an ionic strength of 0.1–0.5, reduced to zero ionic strength, and compared with the literature data. Advantages of colorimetry over spectrophotometry in the determination of the dissociation constants of colored reagents are demonstrated.     

Spectrophotometric simultaneous determination of cobalt, copper and nickel using nitroso-R-salt in alloys by partial least squares

Partial least squares modeling as a powerful multivariate statistical tool applied to spectrophotometric simultaneous determination of cobalt, copper, and nickel in aqueous solutions. The concentration range for cobalt, copper and nickel were 0.4-2.6, 0.6-3.4, 0.5-5.5 ppm, respectively. The experimental calibration set was composed with 36 sample solutions using a mixture design for three component mixtures. The absorption spectra were recorded from 470 to 600 nm. The effect of pH on the sensitivity and selectivity was studied according to net analyte signal (NAS). The values of root mean square difference (RMSD) for cobalt, copper and nickel using partial least squares (PLS) were 0.0192, 0.0263 and 0.0446 ppm, respectively. The effects of various cations and anions were investigated. The method was used to determination of cobalt, copper and nickel in two sample alloys based on copper, nickel and cobalt (known as cunico) and based on cobalt, nickel and iron (known as conife).     

Photometric titrations—V A selective, chelometric determination of cobalt

Cobalt can be titrated with good selectivity by converting it with hydrogen peroxide in alkaline medium to the cobalt^III EDTA complex and back-titrating photometrically in acid medium the excess EDTA with bismuth solution, using pyrocatechol violet as indicator. No interference is observed with alkalies, alkaline earths, Ni, Cu, Cd, Zn, Pb, Al, U, and W. Bi, Zr, In, Ga and other ions forming very stable EDTA complexes are co-titrated. Mo, Fe, Ag and Hg interfere and should be separated. The interference of Mn can be excluded by addition of ascorbic acid. Th can be masked with sulphate. Cr^III is co-titrated, but by applying a difference method operating with two aliquots, both Cr and Co can be determined. Complexing anions interfere, as does chloride, which causes a turbidity with bismuth.     

Photometric determination of niobium with azo-dyestuffs

The azo-dyestuffs, which contain the analytically functional O,O'-dioxyazo group and are widely employed as photometric reagents for niobium, are reviewed. Two new groups of reagents are described : mono-azo-dyestuns based on R-salt and 2,7-bisazo dyestuffs based on chromotropic acid. The reaction with niobium is sensitive (epsilon = 20,000 to 40,000), selective and takes place in strongly acidic solution (0.5-6M hydrochloric or nitric acid). It is possible to extract with butanol the diphenylguanidine salt of the corresponding niobium complex and to measure the absorbance of the extract.     

Photometric determination of selenium with ferrocene

A sensitive spectrophotometric method for the determination of selenium has been developed. The method depends on a redox reaction between selenious acid in 8M hydrochloric acid and a chloroform solution of ferrocene. One mole of selenious acid produces 4 moles of ferricenium ions, which are then oxidized by bromine water. The resulting iron(III) is reduced to iron(II) and determined with 1,10-phenanthroline. The relative standard deviation for 20 mug of selenium was 1.1%. The apparent molar absorptivity of the final solution, referred to selenious acid, is 4.23 x 10(4) 1. mole(-1). cm(-1) at 512 nm. This method has been used to determine selenium in copper metal.     

Photometric determination of malathion with molybdenum

A photometric method for the determination of malathion is described. Malathion dissolved in carbon tetrachloride is hydrolysed at room temperature with sodium ethoxide to dimethyl dithiophosphate (DMDTP) and fumarate. The DMDTP is converted into a molybdenum-DMDTP complex and determined spectrometrically.     

Photometric determination of cobalt by means of photochemically generated anti-2-furaldehyde 2-pyridylhydrazone

The photochemical syn-anti isomerization of 2-furaldehyde 2-pyridylhydrazone (FAPH) in ethanolic solutions has been investigated. A study of the infrared, visible and ultraviolet, and n.m.r. spectra of the two isomers was made. The syn-anti ratio at the photostationary state was determined. syn-FAPH scarcely reacts with metal ions but the anti-FAPH formed by irradiation gives sensitive reactions with several metal ions to form stable chelates. A photometric method for the determination of cobalt (0.025-1.0 microg/ml ) in aqueous ethanolic medium (50% v/v ) at pH 9.7 is described. A detection limit of 0.007 microg/ml and relative standard deviation of 0.5% were found. By consideration of the syn-anti ratio at the photostationary state, the stoichiometry of the chelate was determined. An application of this technique to determination of cobalt in environmental fume samples is also described.     

Photometric determination of gallium with rhodamine b

Gallium is extractable as rhodamine B chlorogallate with benzene from 6M hydrochloric acid, and can be determined absorptiometrically or fluorimetrically in the extract. The interference of iron(III) is avoided by first separating gallium by extraction with isopropyl ether from hydrochloric acid solution containing titanous chloride. Traces of gallium can be determined in the presence of aluminium, indium, zinc, antimony, thallium, tungsten and other elements.     

Photometric determination of tellurium with bismuthiol II

A method for the photometric determination of tellurium based on the extraction of the yellow-coloured complex of tellurium with bismuthiol II is presented. The described method permits the determination of as little as 0.01 % of tellurium in ores directly without preliminary separation. After the isolation of the element by reduction with tin^II chloride even smaller amounts can be determined.     

Photometric determination of boron with oxazine derivatives

Eight oxazine derivatives were examined for their ability to form extractable complexes with boron fluoride. Brilliant cresyl blue, Capri blue and Nile blue form such complexes and can be used as sensitive photometric reagents for boron. Capri blue can even be more sensitive to boron than methylene blue.     

Photometric determination of palladium with dimethylsulphonazo III

A sensitive and selective photometric determination of palladium(II) with dimethylsulphonazo III has been worked out. The effect of many other ions has been investigated.     

Photometric determination of calcium with antipyrylazo III

Antipyrylazo III or diantipyrylazo (3,6-bis(4-antipyrylazo)-4,5-dihydroxy-2, 7-napthalenedisulfonic acid) forms at PH 12.7 a complex Ca₂HL with calcium. The logarithmic overall stability constant, 10g β₂₁₁, is 23.99 ±0.03 (0.1 MNaClO₄,25°C).The effective molar absorptivity is 21,500 ±100 l mole^-1 cm^-1 at 605 nm. The complex can be used for a selective photometric determination of calcium(0.25–3.50μmole) if tri-and tetravalent ions are removed by extraction with cupferron (into chloroform) and transition divalent ions are masked with sodium cyanide. Only strontium (0.5 μmole) and EDTA (0.1 μmole) interfere seriously.     

Photometric determination of nitrite

A new sensitive colour reaction for nitrite determination is presented. The method is based on the reaction of nitrite with p-aminobenzoic acid to form a diazonium ion, which is coupled with 8-hydroxyquinoline, in alkaline medium, to form a reddish-orange water-soluble azo dye. Diazotization and coupling are very fast and control of temperature is unnecessary. Moreover, the colour is stable and its intensity is in direct proportion to nitrite concentration over a wide range.     

Photometric determination of collagen

The interaction of collagen with 2,3,5,6-tetrachloro-p-benzoquinone (chloranil) in a solution containing water and hydrophilic organic solvents was studied. Optimum conditions of this interaction were found. The applicability of chloranil as a reagent for the photometric determination of collagen in a substance and pharmaceutical dosage forms was demonstrated.     

Photometric determination of nitrite

A sensitive colored reaction for nitrite determination is developed. It involves the reaction of the titled ion with p-aminobenzoic acid to form a diazonium ion, which is then coupled with α-naphthol in alkaline medium to form a pinkish red soluble azo dye absorbing maximum at 519 nm. The described method is capable of determining 0.1–1.3 ppm of nitrite with a relative standard deviation of 0.3–1.7% depending on the concentration level, molar absorptivity of 3.5 × 10⁴ liter mol⁻¹ cm⁻¹, and Sandell sensitivity index of 0.0013 μg cm⁻². Diazotization and coupling are very fast and control of temperature is unnecessary. Moreover, the colored azo dye is stable and its intensity is in direct proportion with nitrite concentration over a wide range.     

Photometric determination of tungsten in rocks with trihydroxyfluorones

The interaction of tungsten(VI) with a series of 2,3,7-trihydroxyfluorones in the presence of cationic and non-ionic surfacants has been studied. Optimal conditions for the formation of the complexes and their spectrophotometric determination have been found. Possible mechanisms for the effect of the surfactants are suggested. The method developed has been applied to determination of trace tungsten in rocks and silts.     

Photometric determination of palladium with chrome azurol S

Summary Chrome Azurol S permits a simple colorimetric determination of palladium with a sensitivity of 0.4g/cm² (practical) or 0.04g/cm² (Sandell), respectively. Conditions and interferences are described in detail.

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Zusammenfassung Palladium läßt sich mit Hilfe von Chromazurol S auf einfache Weise kolorimetrisch bestimmen. Die praktische Empfindlichkeit der Methode beträgt 0,4g/cm² bzw. 0,04g/cm² nachSandell. Die Arbeitsbedingungen und die durch Fremdionen verursachten Störungen werden angegeben.

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Résumé Le chromazurol S permet un dosage colorimétrique simple du palladium, avec une sensibilité de 0,4g/cm² (en pratique) ou 0,04g/cm² (Sandell) respectivement. On décrit en détail les conditions opératoires et les interférences.

     

Photometric determination of aluminium with alizarin fluorine blue

In order to decide whether Alizarin Fluorine Blue (alizarin complexan, 3-amino-methylalizarin-N,N-diacetic acid) is a suitable reagent for the spectrophotometric determination of aluminium, values of the stability constants for some reactions of this reagent with aluminium(III) and iron(III) have been determined spectrophotometrically in a medium containing 20 % dioxan and 80 % water at ionic strength 0.1. The values of the constants that were determined are log K(Al)(AlHL) = 14.3, log K(2Al)(Al2L) = 25.3 and log K(Fe)(FeHL) = 19.6. These results were employed in the design of a method for the spectrophotometric determination of aluminium in the presence of iron and titanium. The Sandell sensitivity is 0.01 mug/cm(2) and the coefficient of variation for 34 determinations was 0.9 %.     

Photometric determination of berberine bisulfate

The optimum conditions for the formation of a complex of berberine bisulfate with eosin have been determined. A procedure has been developed for the photometric determination of berberine bisulfate.Vitebsk Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 236–238, March–April, 1989.