Extraction and spectrophotometric determination of cobalt(II) with thiobenzoylacetone and simultaneous determination of cobalt and nickel

Thiobenzoylacetone in benzene is used for the extraction and spectrophotometric determination of cobalt at pH 8.4-9.1. The orange-yellow complex is measured at 460 nm. The system conforms to Beer's law over the range 0.20-4.58 microg ml of extract. The colour of the complex is stable for at least 144 hr. Cobalt(II) is quantitatively extracted and determined in the presence of 200:1 (w w ratios) of various ions. The method is made selective by using common sequestering agents such as thiourea or fluoride or by selective extraction with mesityl oxide, tributylphosphate and acetylacetone. It is possible to determine cobalt in the presence of nickel by simultaneous spectrophotometry. The method is rapid, simple, selective and sensitive.     

Isodifferential derivative approach to the spectrophotometric determination of nickel and cobalt mixtures

A graphical method for measuring derivative amplitudes in binary mixtures with overlapping spectra is described. The method is based on the interference-free character of the isodifferential points in the derivative calibration graphs. Cobalt and nickel mixtures are analyzed in the range 0.01–2.5 μg ml^?1 by the formation of coloured chelates with benzyl-2-pyridylketone 2-pyridylhydrazone, with relative standard deviations ?1.5%.     

Cloud point extraction, preconcentration and simultaneous spectrophotometric determination of nickel and cobalt in water samples

Cloud point extraction has been used for the preconcentration and simultaneous spectrophotometric determination of nickel and cobalt after the formation of a complex with 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA), and latter analysis by spectrophotometer using Triton X-114 as surfactant. The parameters affecting the separation phase and detection process were optimized. Under the optimum experimental conditions (i.e. pH=5, 0.07 mM ACDA, Triton X-114=0.25% (w/v)), calibration graphs were linear in the range of 20-500 and 20-200 microg l(-1) with detection limits of 10 and 7.5 microg l(-1) for Ni and Co, respectively. The method was applied to the determination of Ni and Co in natural and waste water samples with satisfactory results.     

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.     

Extraction and spectrophotometric determination of nickel with 2-hydroxyacetophenone oxime and simultaneous determination of copper and nickel

It is observed that 2-hydroxyacetophenone oxime can be used for the quantitative extraction of nickel in the pH range 6.6-7.8 into methyl isobutyl ketone. The organic layer shows maximum absorbance at 375 nm. Beer's law is obeyed over the range 1-6 ppm. The colour of the organic layer is stable for more than 48 hr. Interferences have been studied and methods are suggested for their elimination. Copper and nickel are both quantitatively extracted at pH 7 and can be determined simultaneously and accurately in the range 1-6 microg/ml for copper and 1-4 microg/ml for nickel.     

Simultaneous spectrophotometric determination of binary mixtures of nickel,cobalt and vanadium with 3-(picolydene)benzenesulphonic acid 2-hydroxybenzoylhydrazone

The synthesis and characterization of a water-soluble reagent, 3-(picolydene)benzenesulphonic acid 2-hydroxybenzoylhydrazone, is described. The reagent is stable in aqueous media. The colour reations with nickel(II), cobalt(III) and vanadium(V) ions in slightly acidic solutions have molar absorptivities in the range 1.4–3.6 × 10⁴ l mol^?1 cm^?1. Simultaneous determinations of Ni, Co and V in binary mixtures are possible. Interference data are reported.     

Simultaneous spectrophotometric determination of traces of cobalt,nickel and copper with dithio-oxamide

The cobalt, nickel and copper complexes of dithio-oxamidc have been characterized in terms of color, effect of pH, structure in solidion, order of addition of reagents, adherence to Beer's law and sensitivity. The reactivity of the reagent to other ions has been reported. A method for the simultaneous spectrophotometric determination of cobalt, nickel and copper has been developed. the results of the application of this procedure to synthetic samples and to several National Bureau of Standards Samples are given.     

Simultaneous spectrophotometric determination of cobalt, nickel and copper with 2,3-quinoxaline- dithiol

In aqueous ethanol cobalt(II), nickel(II) and copper(I) react instantaneously with 2,3-quinoxalinedithiol at pH 2 to form strongly coloured complexes exhibiting absorption maxima at 510, 606 and 665, and 625 nm, respectively. At pH 6 the reaction of copper can be virtually eliminated, while the cobalt and nickel reactions show only small decreases in sensitivity. This behaviour has been made the basis of a rapid method for the simultaneous determination of these three elements. The absorbances of the complexes have been found to be additive for all combinations of these elements in which the individual concentrations have been varied from approximately 0.1 to 1 ppm. A least-squares estimate of the concentration of any of the elements may be readily obtained by using a simple linear equation based on the absorbance readings and a set of constants derived from the spectrophotometric data. The analyses of seven synthetic solutions and four NBS Standard Reference Materials yielded a maximum error of 6.0% and an average error of 1.6%.     

Chemometrics-assisted spectrophotometric method for simultaneous determination of vitamins in complex mixtures

An advanced independent component analysis algorithm (MILCA) is applied for simultaneous chemometric determination of fat- and water-soluble vitamins in complex mixtures. The analysis is based on the decomposition of spectra of multicomponent mixtures in the UV region. The key features of the proposed method are simplicity, accuracy, and reliability. Comparisons between the new algorithm and other established methods (MCR-ALS, SIMPLISMA, other ICA techniques) were made. Our results indicate that in most cases, MILCA is comparable or even outperforms other chemometrics methods taken for comparisons. The influence of different factors (abundance of components, noise, step of spectral scan, and scan speed) on decomposition performance has been investigated. The optimal conditions for spectroscopic registration have been identified. The proposed method was used for analysis of model mixtures and real objects (multivitamin drugs, food additives, and energy drinks). The resolved concentrations match well with the declared amounts and the results of reference methods.     

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.     

Improved method for the simultaneous absorptiometric determination of cobalt and nickel with quinoxaline-2,3-dithiol

A new, more stable reagent, S-2-(3-mercaptoquinoxalinyl)thiuronium chloride (MQT), is proposed for the simultaneous absorptiometric determination of cobalt and nickel. It is hydrolysed rapidly to quinoxaline-2,3-dithiol (QDT) in ammonia buffer at pH 10. In the presence of zinc(II), QDT is stabilized by complex formation and the reagent blanks are reduced. Samples containing cobalt(II) and nickel(II) react with the mixture on warming to give 1:3 cobalt and 1:2 nickel complexes, with maximum absorbances at 472 and 520 mmu respectively. The sensitivity of the method is high, 0.0017 and 0.0028 mug cm (2) for cobalt and nickel respectively, and there is a significant improvement in accuracy and precision, which is about +/-1 % over a 15-fold change in cobalt to nickel ratio. The selectivity is moderate; Ag(I), Cu(II), Pd(II), Cd(II), Hg(II), Sn(II), Pb(II), Bi(III) and Pt(IV) cause significant interference but most other common cations and anions can be tolerated.     

Simultaneous spectrophotometric determination of cobalt and nickel by partial least square regression in micellar media

Diphenycarbazone has been used for the simultaneous determination of cobalt and nickel by partial least square regression method. DPC complexes of cobalt and nickel at pH 7-10 are of pink color, which are soluble in TX-100 micellar media. A partial least square multivariate calibration method for the analysis of binary mixtures of cobalt and nickel was developed. The total relative standard error for applying the PLS method was calculated. The accuracy and reproducibility of the determination method for various known amounts of Co(II) and Ni(II) in their binary mixtures were tested. The effects of diverse ions on the determination of cobalt and nickel to investigate the selectivity of the method were also studied. The proposed method was applied to the synthetic binary mixtures, alloys and pharmaceutical samples.     

Process monitored spectrophotometric titration coupled with chemometrics for simultaneous determination of mixtures of weak acids

A new spectrophotometric titration method coupled with chemometrics for the simultaneous determination of mixtures of weak acids has been developed. In this method, the titrant is a mixture of sodium hydroxide and an acid-base indicator, and the indicator is used to monitor the titration process. In a process of titration, both the added volume of titrant and the solution acidity at each titration point can be obtained simultaneously from an absorption spectrum by least square algorithm, and then the concentration of each component in the mixture can be obtained from the titration curves by principal component regression. The method only needs the information of absorbance spectra to obtain the analytical results, and is free of volumetric measurements. The analyses are independent of titration end point and do not need the accurate values of dissociation constants of the indicator and the acids. The method has been applied to the simultaneous determination of the mixtures of benzoic acid and salicylic acid, and the mixtures of phenol, o-chlorophenol and p-chlorophenol with satisfactory results.     

Detection and spectrophotometric determination of cobalt with dimedone dioxime

Dimedone dioxime forms coloured complexes only with cobalt, nickel and copper ions in alkaline solution. Acidification and solvent extraction enables cobalt (1-50 mug) to be determined spectrophotometrically without interference. A specific spot test for cobalt is based on the same reaction.