Liquid-liquid extraction and simultaneously spectrophotometric determination of Co (II) and W (VI) using crown ether (DB-18-C6) in aqueous media and in high speed steel (original) (raw)
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Chemical Papers, 2006
A new ternary ion-association complex of tungsten(VI), 4-nitrocatechol (NC), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (Thiazolyl Blue, MTT) was obtained and studied using an extraction-spectrophotometric method. The optimum pH, reagent concentrations, and extraction time were determined. The composition of the complex was found to be W(VI): NC: MTT = 1: 2: 2. The extraction process was investigated quantitatively and the key constants were calculated. The molar absorptivity of the chloroform extract at λmax = 415 nm was 2.8 × 104 dm3 mol−1 cm−1, and the Beer’s law was obeyed up to 8.8 μg cm−3 tungsten(IV). The limit of detection and limit of quantification were calculated to be 0.27 μg cm−3 and 0.92 μg cm−3, respectively. The effect of foreign ions and reagents was studied and a competitive method for determination of tungsten in products from ferrous metallurgy was developed. The residual standard deviation and the relative error were 0.53 % and 0.2 %, respectively.
Some organic reagents have been used in the gravimetric determination of tungsten 1-6, but the scope of application of these methods is limited. The use of N-phenylbenzohydroxamic acid (PBHA) has also been recommended 7 but the method is neither selective nor sensitive. According to the data given in the literature s several ions such as Nb, Ta, Ti(IV), Zr, Hf, Sn(IV), Mo(VI) and Ge, would interfere under the conditions used.
Annali di Chimica, 2004
The extraction and spectrophotometric determination of trace amount of molybdenum(VI) with 2-hydroxy-5-methylacetophenoneisonicotinoylhydrazone (HMAINH) has been studied. The method is simple, selective, rapid and highly sensitive: reagent HMAINH forms a 1:2 yellow coloured complex with Mo(VI). The complex shows absorption maxima at 410 nm, where as absorption due to reagent is negligible. The extraction was carried out at 0.015 M-0.018 M hydrochloric acid into MIBK. Beer's law is obeyed over the concentration range of 3-16 ppm of molybdenum(VI) at 410 nm. Optimum range as defined by Ringbom's plot was 4-12 ppm. The molar absorptivity and Sandell's sensitivity of extracted species are 5.643 χ ΙΟ 3 dm 3 mor'cm" 1 and 17 ng cm " 2 respectively. The standard deviation was found to be 0.09718. The effect of various diverse ions on the estimation of Mo (VI) has been studied. The method is applied for the determination of molybdenum in alloys.
Coloration Technology, 2008
Hydroxy-2-[1¢-phenyl-3¢-(p-chlorophenyl)-4¢-pyrazolyl]-4-oxo-4H-1-benzopyran solution in acetone forms a yellow-coloured complex with tungsten(VI) in perchloric acid medium which is extractable into chloroform after equilibration. In this study, tests were carried out on this compound and it was found to be quite stable and to obey Beer's law. Interactions with various ions were studied and the molar absorptivity, Sandell's sensitivity and relative standard deviation were also investigated. Job's method, the mole ratio method and the equilibrium-shift method were also used. The ratio of metal to ligand was measured using a method that was simpler, more accurate, sensitive, rapid and selective as compared with existing methods. This method is applicable to the analysis of various samples of varied composition.
Talanta, 2006
A flow-injection procedure for simultaneous spectrophotometric determination of tungsten and molybdenum in steel alloys is proposed. The method exploits the catalytic effects of Mo(VI) and W(VI) on the rate of iodide oxidation by hydrogen peroxide under acidic conditions. A novel strategy for ion-exchange separation of the potential interfering species is proposed, and an AG50W-X8 cationic resin mini-column is used. The sample is injected twice, originating two sequential plugs, citrate being added to one of them in order to suppress the W(VI) catalytic activity thus providing the kinetic discrimination. The system handles 70 samples per hour and requires 1.6 mg KI per determination. A linear response is verified up to 10 mg l −1 Mo (or W) in the injectate, and signal additivity is 98-103%. Results are precise (R.S.D. < 0.04) and in agreement with ICP-OES. Running a standard reference material (IPT-50) assessed also accuracy.
Liquid Ion Exchange with Spectrophotometric Method for Separation and Determination W (VI
Jour of Adv Research in Dynamical & Control Systems, 2019
Liquid ion exchange method as sensitive application of solvent extraction in order to separation and determination W(V1) as anion WO 4-2 by use α-Naphthyl amine to formation ion pair association complex, spectrophotometric study shows the wave length for maximum absorbance of ion pair association complex was λ max =289nm, effect of HCl concentration on extraction efficiency of WO-2 demonstrate 0.6M HCL was the optimum concentration of HCL to give higher extraction efficiency in presence 50Mg W(V1)/5ml by using 1x10-4 M p-naphthyl amine (α-NPA) dissolved in chloroform. The optimum condition for highest extraction W(V1) as WO 4 +2 appear the method of extraction needed shaking time equal to 15 min. the existance of electrolyte in aqueous solution effect to increase the extraction efficiency of W(V1), and this enhancement in extraction efficiency differ with different electrolyte and concentration, thermodynamic study shows extraction method was endothermic and the optimum temperature was 40˚C and thermodynamic data were ∆H ex = 0.1273KJmol-1 ∆G ex =-67.136 KJmol-1 ∆S ex = 214.898 Jmol-1 K-1 , stoichiometry shows the more probable structure of ion pair association complex extracted was [H-PNA] + ; HWO 4-, the study involved also interferences effect. And spectrophotometric Determination.
Talanta, 2005
A new functionalized calix[6]crown hydroxamic acid is reported for the speciation, liquid-liquid extraction, sequential separation and trace determination of Cr(III), Mo(VI) and W(VI). Chromium(III), molybdenum(VI) and tungsten(VI) are extracted at pH 4.5, 1.5 M HCl and 6.0 M HCl, respectively with calixcrown hydroxamic acid (37,38,39,40,41,42-hexahydroxy7,25,31-calix[6]crown hydroxamic acid) in chloroform in presence of large number of cations and anions. The extraction mechanism is investigated. The various extraction parameters, appropriate pH/M HCl, choice of solvent, effect of the reagent concentration, temperature and distribution constant have been studied. The speciation, preconcentration and kinetic of transport has been investigated. The maximum transport is observed 35, 45 and 30 min for chromium(III), molybdenum(VI) and tungsten(IV), respectively. For trace determination the extracts were directly inserted into the plasma for inductively coupled plasma atomic emission spectrometry, ICP-AES, measurements of chromium, molybdenum and tungsten which increase the sensitivity by 30-fold, with detection limits of 3 ng ml −1 . The method is applied for the determination of chromium, molybdenum and tungsten in high purity grade ores, biological and environmental samples. The chromium was recovered from the effluent of electroplating industries.
Selective extractive spectrophotometric determination of cobalt using cyanex 923
Indian Journal of Chemical Technology, 2004
The present paper describes a selective extractive spectrophotometric method for the determination of Co (II ) lIsin g toluene solution of cyanex 923. A blue coloured complex (A."", 685 nm) is quantitatively extracted in th e organic phase fro m 7- 10 mo l L , HCI. The compositi on of this complex is proposed as H l CoCl 4 .2cyanex 923 . The Beer 's law is obeyed in th e concentrati on range 0 .0- 4.2 x 10-) mol L-' Co(ll) and the molar absorptivity of the complex is 5.6 x 10 2 L mol-' c m-'. The presence of hundred fold excess of metal ions such as Mo(VI), W(VI) , V(V), Ti(lV), V(lV), AI("' ), Cr(lll ), Fe("'), Mn(" ), Fe(" ), Ni("), Cu(II) , Zn(lI ) and Cd(I1) and fifty fold of anions namely P04 )-, SO.I- , Cp. l -, citrate, tartrate, NO)- and SCN· do not interfe re in the determination of Co(ll). The accuracy of proposed procedure is checked by assaying the conc entration of cobalt in two standard NBS steel samples. The ...
Journal of Electroanalytical Chemistry, 2010
The renewable mercury film electrode, applied for the determination of tungsten(VI) ultra traces using differential pulse catalytic adsorptive cathodic stripping voltammetry (DP CAdSV) with presence of catechol as a ligand and chlorate(V) is presented. The calibration graph obtained for W(VI) is linear from 0.025 nM (4.5 ng L À1) to 130 nM (23.9 lg L À1) for a preconcentration time of 30 s, with correlation coefficient of 0.9989. For the renewable mercury electrode (Hg(Ag)FE) with a surface area of 4.4 mm 2 the detection limit for a preconcentration time of 60 s is as low as 0.2 ng L À1. The repeatability of the method at a concentration level of the analyte as low as 0.09 lg L À1 , expressed as RSD is 3.1% (n = 5). The proposed method was successfully applied and validated by studying the certified reference material CTA-VTL-2 and simultaneously recovery of W(VI) from spiked water samples.
Spectrophotometric studies and liquid-liquid extraction of Fe(III) and Co(II) using azo ligand 1,5-dimethyl-2-phenyl-4-[(E)-(2, 3, 4-trihydroxyl phenyl) diazinyl]-1,2-dihydro-3H-pyrazole-3-one (H3L) were carried out using CHCl3 and CH2Cl2 as solvents, respectively. The azo ligand and its metal complexes were synthesized and characterized. Stoichi-ometric study of the ligand to metal using Job continuous variation method was 2:1 [Fe(H2L) 2] + , [Co (H2L)2]. The conductivity test of the ligand and its complexes showed slight conducting properties. The IR spectral of H3L and its Fe(III) and Co(II) complexes showed that the metals coordinated through hydroxyl, azo, nitrogen and carbonyl group. The potential determination of pKb (8.37) and pKa (5.63) indicated that H3L can be protonated and deprotonated. The spectrophotomet-ric analysis of Fe(III) and Co(II) were carried out with potassium thiocynate in acetone and ammonium thiocynate in ace-tone which gave red colouration and blue colouration, respectively. The liquid-liquid extraction of Fe(III) from steel was quantitative at pH 6 and in 0.001 M HClO4 up to 96% was extracted at 5 min, while Co(II) extraction was quantitative up to 80.2% was extracted at pH 11 in 0.001 M H2SO4 at 5 min. Thus, azo ligand (H3L) is a promising extractant for Fe(III) and Co(II) ions.