Use of nitrosochromotropic acid as a metal indicator

Summary Nitrosochromotropic acid and copper give a purple coloured complex in the pH range 5.8–6.5, which is less stable than Cu(II)-EDTA complex. When milligramme quantities of copper solution containing few drops of nitrosochromotropic acid were titrated with EDTA the colour changes to light green or colourless. Copper can be titrated from 15–30° C, but at higher temperature low results are obtained due to dissociation of copper complex. Alkaline earths do not interfere in the titration of copper, but zinc, cadmium, nickel, cobalt, aluminium and iron(III) interfere. The interference of aluminium and iron(III) is masked by sodium fluoride. Microtitration can be carried out using nitrosochromotropic acid screened with xylene cyanol FF as metal indicator.     

Synthesis and Spectrophotometric Studies of 2-(2-Imidazolylazo)-5- Dicthylamino Phenol

Inasearchfornewsensitiveandselectiveorganicreagents,athoroughstudyofslomeofthequinolylazo,pridylazocompoundshasbeenreported.'-'Buttriazolylazoandimidazolylazocompoundshavenotbeenstudied.Inanearliespaper,'wehavereportedthesynthesisandspectrophotometricstudiesof2-(l,3,4-triazolylazo)-5-diethy\phenoland2-(5-carboxy-l,3,4-triazolylazo)phenol.Inthispaper,2-(2imidazolylazo)-5-diethylaminophenol(IZAPN)wasprepared,theconditionsofitsreactionwithcobaltwerestudied.Itwasfoundthatthereagenthadhighsensiti…     

Synthesis and Spectrophotometric Studies of 2-(1, 3, 4 -Triazolylazo) -5-Diethylamino Phenol and 2-(5-Carboxy-1, 3, 4-Triazolylazo) -5- Diethylamino Phenol

Inasearchfornewsensitiveandselectiveorganicreagents,athoroughstudyofsomeofthequinolylazo,pyridylazocompoundshasbeenreported'-'.Buttriazolylazocompoundshavenotbeenstudied.Inthispapef,2-(l,3,4-triazolylazo)-5-diethyIaminophenol(TZAPN)and2-(5-carboxy-l,3,4-triazoiylazo)-diethyIaminophenoI(CTZAPN)wereprepared,theconditionsofthisreactionwithcobaltwerestudied.Itwasfoundthatthereagentshadhighsensitivityandselectivityinthedeterminationofmicrogramamountsofcobaltundertheconditionsestablished.Thest…     

Spectrophotometric determination of cobalt(II) with 2-(3′-sulfobenzoyl)pyridine benzoylhydrazone

A simple method has been described for the Spectrophotometric determination of cobalt(II) with 2-(3′-sulfobenzoyl)pyridine benzoylhydrazone (SBPBH). In aqueous solution, cobalt(II) reacts with SBPBH to form a yellow complex, which is not destroyed even by the addition of 3.8 M perchloric acid. The absorption maximum of the complex in 1.5 M perchloric acid medium was found to be 400 nm; the molar absorptivity was 2.17 × 10⁴ liters mol⁻¹ cm⁻¹. The proposed method is fairly selective and has been applied to the determination of cobalt in standard alloy steel samples.     

High enrichment method for the determination of ultra-trace levels of cobalt by liquid—liquid extraction using water/oil/water emulsions as liquid surfactant membranes

A high preconcentration method for the determination of cobalt by graphie furnace atomic absorption spectrometry using liquid surfactant membranes was developed. Droplets of dilute hydrochloric acid in kerosene containing 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester emulsion coated with sorbitan monooleate are dispersed in an aqueous sample solution. Cobalt(II) diffuses through the liquid membrane to form the complex with the ester and the analyte ion is extracted successively into the inner acidic aqueous phase. A 550-fold enrichment of cobalt(II) and a detection limit of 10 pg ml^?1 are achieved.     

Spectrophotometric Determination of Cobalt in Vitamin Preparations,Steel and Iron Using 2-Hydroxy- 1-Naphthaldehyde Guanylhydrazone

Abstract

A new spectrophotometric determination of cobalt with 2-hydroxy-1-naphthaldehyde guanylhydrazone in acid medium is described. The method is developed on the basis of a yellow cobalt (III) complex (molar absorptivity 1.32×10^?4 L.mol^?1.cm^?1 at 416 nm, stoichiometry 2:1). The method was applied to the determination of cobalt in vitamin preparations, steel and high-purity iron.     

新显色剂2-(2-噻唑偶氮)-5-二乙氨基苯甲酸分光光度法测定微量钴

近年来,杂环偶氮苯甲酸类显色剂取得了较快的发展。由于氨基取代结构对试剂性能有较大的影响^[1],因此本文合成了新显色剂2-(2-噻唑偶氮)-5-二乙氨基苯甲酸,(TAEB)并研究了它与钴的显色反应。     

高效毛细管电泳法测定镍盐中的钴含量

用２－亚硝基－１－萘酚－５－磺酸与Ｎｉ、Ｃｏ络合,在波长５３０ｎｍ和其他优化测定条件下,用高效毛细管电泳法定量测定市售镍盐中微量钴,为测定镍 微量钴提供了一种快速,简便的新方法。     

Study of 2-(2-quinolinylazo)-5-dimethylaminobenzoic acid as a new chromogenic reagent for the spectrophotometric determination of cobalt

2-(2-Quinolinylazo)-5-dimethylaminobenzoic acid (QADMAB) is proposed as a new sensitive and selective chromogenic reagent for spectrophotometric determination of cobalt. The QADMAB reacts with cobalt in the presence of cetyl trimethylammonium bromide (CTMAB) medium to form a violet complex of molar ratio 1:2 (cobalt to QADMAB) in the pH range 3.2-5.2. The molar absorptivity of the complex is 1.28x10(5) L mol(-1) cm(-1) at 625 nm. Beer's law is obeyed in range 0.01-0.32 micro g mL(-1). The relative standard deviation for eleven replicate samples of 0.2 micro g mL(-1) is 0.76%. This method was applied to the determination of cobalt in biological samples, Vitamin B(12), alloys and water with good results.     

meso-四-(3-N-甲基吡啶)卟啉与钴反应的分光光度研究

水溶性卟啉衍生物作为光度试剂在分析化学中已得到广泛的应用。在测定某些过渡金属元素时具有极高的灵敏度(ε值为2-5×10⁵)^[1]。meso-四-(3-N-甲基吡啶)卟啉[T(3-MPy)P]与铜^[2]、锌^[3]、铅^[4]的反应都已进行研究。本文对T(3-MPy)P与钴的反应进行了初步的研究。T(3-MPy)P的结构如右图。     

Spectrophotometric determination of cyanocobalamin (as cobalt)

A spectrophotometric method for the determination of cyanocobalamin (as cobalt) in pharmaceutical preparations has been developed. The sample is first decomposed with sulfuric acid and potassium perchlorate. The liberated cobalt is then determined using 2,2′-dipyridyl-2-pyridylhydrazone as reagent in solutions containing 20% sulfuric acid. The presence of other metal cations does not interfere with the determination of cobalt. The method has been applied to the determination of cobalt in pure cyanocobalamin and in two pharmaceutical preparations.     

5-(5-氟-2-吡啶偶氮)-2,4-二氨基甲苯与钴显色反应的研究及应用

研究了新合成试剂5-(5-氟-2-吡啶偶氮)-2,4-二氨基甲苯(5-F-PADAT)与钴(Ⅱ)的显色反应。实验表明,在pH4.7~9.0范围内,钴与试剂形成紫红色配合物,其最大吸收波长位于506 nm。该配合物在无机酸作用下,可转化为另一具有较高吸收特性的质子化型体,最大吸收波长红移到565 nm,适宜的酸浓度范围分别为:0.24~3.6 mol/L HClO4、0.16~3.84 mol/L H2SO4、0.48~2.4 mol/L HCl、0.64~3.84 mol/L H3PO4。配合物表观摩尔吸光系数ε565=9.1×104L.mol-1.cm-1,钴(Ⅱ)质量浓度在0~0.5μg/mL内符合比尔定律。所拟方法已应用于维生素B12针剂中微量钴的测定。     

Trace determination of cobalt ion by using malic acid-malonic acid double substrate oscillating chemical system

A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated. The method is based on adding malic acid into classical Belousov-Zhabotinskii （B-Z） oscillating chemical system to form a double substrate one. The results showed that when the concentration of cobalt ion was in the range of 5.27× 10^-8 to 5.37 × 10^-12 mol L^-1, the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration. The sensitivity and precision of the developed method were quite satisfactory. The limit of detection was down to 5.20 × 10^-13 mol L^-1 which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far. Some factors influencing the determination were also examined. The method has been successfully used to determine cobalt ion in vitamin B12 injection.     

分光光度法同时测定微量铁和钴

在碱性介质中,铁(Ⅱ)和钴(Ⅱ)可与硫代巴比妥酸-NO2-体系反应分别形成一种稳定的兰色和黄色配合物,铁(Ⅱ)配合物在656nm和386nm具有吸收峰,钴(Ⅱ)配合物只有一个吸收峰位于423nm,体系的吸光度A6Fe56、A4F2e3、AC42o3与铁、钴含量在一定的范围内呈良好的线性关系,且铁(Ⅱ)、钴(Ⅱ)配合物在423nm波长处的吸光度具有良好的加和性,建立了一种同时测定微量铁和钴的新的分光光度法。方法的线性范围分别为铁0～50μg/(25mL)、钴0～25μg/(25mL)。将该法应用于水样中微量铁和钴的同时测定,其结果分别与原子吸收光谱法和紫尿酸光度法相吻合,加标回收率分别为98%～102%和94%～106%,相对标准偏差(RSD)分别为1.0%～1.8%和3.1%～4.7%(n=5)。     

Sequential potentiometric complexometric redox determination of iron(III) and cobalt(II) with application to alloys

A simple potentiometric method is presented for successive determination of iron(III) and cobalt(II) by complexometric titration of the iron(III) with EDTA at pH 2 and 40 degrees , followed by redox titration of the cobalt(II) complex with 1,10-phenanthroline or 2,2'-bipyridyl at pH 4-5 and 40 degrees , with gold(III). There is no interference in either determination from common metal ions other than copper(II), which severely affects the cobalt determination but can be removed by electrolysis. The method has been successfully applied to determination of iron and cobalt in Kovar and Alnico magnet alloys.     

Extraction and spectrophotometric determination of zinc in coal fly ash and pond sediments with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of zinc with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid. The reagent forms a stable, blue 1:2 zinc/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the zinc(II) complex is 1.26 × 10⁵ l mol^?1 cm^?1 at 610 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper and nickel can be masked with dimethylglyoxime and aluminium and iron with a mixture of sodium fluoride and triethanolamine. The method is applied to the determination of zinc in coal fly ash and pond sediments with good precision and accuracy.     

Extraction and spectrophotometric determination of cobalt with dithizone

Cobalt(II) in acetate-tartrate buffer (pH 6.0-7.3) is extracted quantitatively as cobalt(III) dithizonate with excess of dithizone in CCl(4). The molar absorptivity in the CCl(4) phase is 4.6 x 10(4) 1.mole(-1).cm(-1) at the absorption maximum 550 nm. The calibration graph is linear for 1-10 mug of cobalt in 10 ml of CCl(4) when excess of dithizone is removed by back-extraction with 0.01M aqueous ammonia. Most interferences can be overcome by (a) initial extraction with dithizone at pH 1.3, (b) selective back-extraction into hydrochloric acid (pH 1 to 2), (c) oxidation of iron and tin to iron(III) and tin(IV) and addition of fluoride to complex the former, and (d) selective reaction of nickel dithizonate with 1,10-phenanthroline in the CCl(4) phase followed by back-extraction of nickel into 0.1M acid. The method has been applied to determination of cobalt in a copper-nickel-zinc alloy and a nimonic alloy.     

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 degrees 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%.     

Extraction and spectrophotometric determination of cobalt(II) with isonitroso-5-methyl-2-hexanone

A simple and selective method is proposed for the extraction of cobalt(II) for its spectrophotometric determination using (HIMH) as an extractant. Cobalt(II) forms a yellow coloured complex with HIMH which can be extracted into chloroform. The calibration curve is rectilinear in the concentration range 0.1–5.0 μg ml⁻¹ of cobalt(II). The extracted species shows an absorption maximum at 400 nm with molar absorptivity of 1.135×10⁴ l mol⁻¹ cm⁻¹. The method has been applied for the determination of cobalt in synthetic mixtures, pharmaceutical, biological and high speed steel samples.     

Extraction spectrophotometric determination of cobalt and nickel using ethylthioxanthate

A spectrophotometric method for the determination of cobalt and nickel using a new reagent sodium ethylthioxanthate has been described. The yellow-colored cobalt complex and red-colored nickel complex have been extracted quantitatively using carbon tetrachloride in the pH ranges 4.0–11 and 4.0–6.7, respectively. The colors of these complexes are stable and absorbances have been measured at 389 nm for cobalt and 495 nm for the nickel complexes. Few ions interfere but the method has been applied successfully for the determination of these metal ions in various complex materials.