Extractive-spectrophotometric determination of molybdenum as mixed-ligand complexes with thiocyanate and amidopyridines

A fairly selective and sensitive method is described for the determination of microgram amounts of molybdenum(V) by means of its reaction with thiocyanate and the enolic form of various amidopyridines and extraction into benzene. The molar absorptivity of the complexes is in the range 1.5-1.9 x 10(4) l.mole(-1).cm(-1) at lambda(max) 470 nm. The method is applicable in 1.5-7M hydrochloric acid or 1.2-6(M) sulphuric acid media. Cu(+), Co(2+), Mn(2+), Zn(2+), Ni(2+), Cd(2+), Fe(3+), Al(3+), Cr(3+), Ti(4+), Zr(4+), V(V), Nb(5+), Ta(5+), W(VI) and U(VI) do not interfere.     

The extraction and determination of molybdenum as the thiocyanate complex

A method is presented for the determination of molybdenum by extraction of its thiocyanate complex with methyl isobutyl ketone. The method is accurate to ±4% or 3 μg of molybdenum, whichever is greater. The only elements which cause interference are rhenium (serious), platinum, palladium, rhodium, selenium and tellurium. The method has been applied to a number of standard samples with excellent results.     

Extractive-spectrophotometric determination of molybdenum with 4-unsubstituted-5-pyrazolones

A fairly sensitive and selective method for rapid determination of tracer amounts of molybdenum(V) as mixed-ligand complexes with thiocyanate and 4-unsubstituted-5-pyrazolones is described. The red complexes are extractable into chloroform from 1-5M hydrochloric or perchloric acid or 1-3M sulphuric arid media. The molar absorptivities are in the range 1.72-2.15 x 10(4)l.mole(-1).cm(-1) at 455 nm (lambda(max)). The method has been applied to the estimation of molybdenum in various synthetic and alloy-steel samples. In presence of excess of the reagent, Cu(II), Co(II), Mn(II), Fe(II), Fe(III), Al(III), Cr(III), Cr(VI), Ti(III), Ti(IV), Zr(IV), Hf(IV), V(III), V(IV), V(V), Nb(V), Ta(V), W(VI) and U(VI) do not interfere.     

Fluorimetric determination of methylmercury as an ion-association complex with rhodamine B in the presence of iodide

A fluorimetric method for the determination of methylmercury was established. The method was based on the formation of an ionic pair between iodide-methylmercury-rhodamine B in hydrochloric acid, which can be extracted with benzene. The fluorescence emission was measured at λ_ex/λ_em 575/590 nm, and the experimental variables and possible interference were studied. The linear calibration range was 4 × 10^–8 mol/L ～ 5 × 10^–7 mol/L with a correlation coefficient of 0.9992. The detection limit was 1 × 10^–8 mol/L. The method was used to determine methylmercury in human hair. The recovery was in the range of 91% to 105% and the relative standard deviation was 2.8%. The results agreed with those obtained by gas chromatography with electron capture detection.     

Fluorimetric determination of methylmercury as an ion-association complex with rhodamine B in the presence of iodide

A fluorimetric method for the determination of methylmercury was established. The method was based on the formation of an ionic pair between iodide-methylmercury-rhodamine B in hydrochloric acid, which can be extracted with benzene. The fluorescence emission was measured at lambda(ex)/lambda(em) 575/590 nm, and the experimental variables and possible interference were studied. The linear calibration range was 4 x 10(-8) mol/L to approximately 5 x 10(-7) mol/L with a correlation coefficient of 0.9992. The detection limit was 1 x 10(-8) mol/L. The method was used to determine methylmercury in human hair. The recovery was in the range of 91% to 105% and the relative standard deviation was 2.8%. The results agreed with those obtained by gas chromatography with electron capture detection.     

Extractive-spectrophotometric determination of tin as Sn(II)-ferron complex

Summary Tin(II) forms a yellow coloured complex with ferron which can be extracted into tribenzylamine-chloroform solution from dilute hydrochloric acid medium. Tin is determined spectrophotometrically by measuring the absorbance at 390 nm. Beer's law is valid up to 7 g Sn/ml with a sensitivity of 0.02 g Sn/cm². Chromium, manganese, iron, nickel, cobalt, copper, zinc, lead, magnesium, titanium, thorium, uranium and vanadium do not interfere. The method is quite simple and useful; its applicability has been tested by the analysis of synthetic samples and an alloy sample of gun metal.     

Spectrophotometric determination of molybdenum in rocks with thiocyanate

A rapid procedure for the determination of microgram amounts of molybdenum in rocks is described. After acid decomposition, molybdenum is extracted from a hydrochloric acid solution into xylene with tributyl phosphate. After back-extraction with water, molybdenum is extracted as the α-benzoinoximate into chloroform, stripped into hydrochloric acid extracted as the thiocyanate into amyl alcohol, and determined spectrophotometrically. The molybdenum thiocyanate color produced is stable, sensitive, and reproducible. Results of analyses of several of the U.S. Geological Survey standard rocks are given.     

The absorptiometric determination of molybdenum as molybdenum(v) thiocyanate in steel

The absorptiometric thiocyanate method for molybdenum has been thoroughly studied with regard to the role of the following reagents: HC1, H₂SO₄, HClO₄, KSCN, SnCl₂ and Fe. A method is described, which allows the determination of 0.01–10% Mo in steel with a relative standard deviation of less than 0.5%. The only interferences (slight) are Nb and the combination V and W. The method gives better than 99.8% recoveries. Results for the determination of molybdenum in standard samples are presented.     

Colorimetric determination of molybdenum by the reaction with thiocyanate

Summary A new method for the photometric determination of micro quantities of molybdenum through the thiocyanate method has been developed. The reduction of Mo VI to Mo V is achieved by photochemical reaction at 2 N acidity without the addition of an extraneous reducing agent. The coloured complex is stable for about 36 hrs. in 2.0N acid concentration. The method is accurate to about ±1.0% and Beer's Law is obeyed within the limits of 0 to 100 g.

---

Zusammenfassung Ein Verfahren zur photometrischen Bestimmung von Mikromengen MolybdÄn mit der Thiocyanatmethode wird beschrieben. Die Reduktion von Mo^VI zu Mo^V wird durch photochemische Reaktion in 2 n saurem Medium ohne Zusatz eines weiteren Reduktionsmittels erreicht. In diesem SÄuremedium ist der Farbkomplex etwa 36 Std lang stabil. Die erhaltenen Werte sind auf ±1,0% genau und das Beersche Gesetz wird von 0–100 g befolgt.

     

Spectrophotometric determination of tellurium in trace quantities by use of an ion-association complex

The formation of an ion-association complex by the interaction of iodotellurate(IV) with cetyltrimethylammonium bromide is used as the basis of an extractive procedure to determine tellurium in the range 2.5-12.5 mug in a final aqueous phase volume of 20 ml. The method is simple, reliable and sensitive. Selectivity is achieved by separation of tellurium on aluminium hydroxide as collector.     

Spectrophotometric determination of molybdenum with thiocyanate after extraction of the tetraphenylarsonium and tetraphenylphosphonium complexes

Microchimica Acta - Spectrophotometric determination of molybdenum with thiocyanate by extraction of the tetraphenylarsonium and tetraphenylphosphonium ion-association complexes is described....     

Investigation of the extraction equilibrium of ion-association complexes of molybdenum (VI) with some polyphenols and thiazolyl blue. extraction-spectrophotometric determination of molybdenum

The extraction process of ternary ion-association complexes of molybdenum (VI) with some polyphenols (4-nitrocatechol, 2,3-dihydroxy naphthalene) and thiazolyl blue has been investigated by using an extraction-spectrophotometric method. The optimum conditions for their quantitative preparation in aqueous medium and subsequent extraction into an organic solvent have been found. The extraction, distribution and association constants, and the recovery factors have been calculated. The composition of the complexes has been determined. A precise, sensitive and simple extraction-spectrophotometric method for determination of molybdenum in products from ferrous metallurgy has been developed.     

Spectrophotometric determination of molybdenum(VI) with 2-mercaptobenzo-γ-thiopyrone and ammonium thiocyanate

Molybdenum(VI) in 1.4–3.6 M hydrochloric acid medium forms an acetophenone-extractable orange-red complex with the potassium salt of 2-mercapto-benzo-γ-thiopyrone and ammonium thiocyanate in the presence of tin(II) chloride. The limit of identification of the spot test based on this reaction is 0.1 μg of molybdenum (dilution limit, 1:1·10⁶). The spectrophotometric method is fairly selective, the sensitivity being 0.005μg Mo cm^-2 at 470 nm. The colour system obeys Beer's law; the optimal concentration range is 0.75–8.5 μg Mo ml^-1, the relative photometric error being 1.675%. The complex is stable for over 24 h. Common ions can be tolerated in amounts greater than 1000-fold. Interferences of Co²⁺, Ni²⁺, Cu²⁺ and Ag⁺ are avoided by complexing these ions with 2-mercaptobenzo-γ-thiopyrone at pH 6–10 and extracting with ethyl acetate or chloroform. The proposed method is applied to the determination of molybdenum in steel and in artificial mixtures.     

Spectrophotometric determination of molybdenum by extraction as the molybdenum-quinoline-thiocyanate mixed complex

Summary Molybdenum (VI) is reduced to the pentavalent state very rapidly in the presence of thiocyanate and quinoline (or similar bases) in 2.5M hydrochloric acid medium. It distributes into nitrobenzene as [MoO(Qn)₂(SCN)₃] giving a orange red extract with maximum absorbance at 470 nm and molar absorbance 18 000 ±200. The system obeys Beer's law up to 5g of Mo per ml. Cu(II), Fe(III), Ti(IV) and W(VI) interfere; but methods have been developed for the elimination of interference.

---

Zusammenfassung Molybdän (VI) wird in Gegenwart von Thiocyanat und Chinolin (oder ähnlichen Basen) in 2,5-m Salzsäure sehr rasch zu Mo(V) reduziert. Dieses wird als [MoO(Chin)₂(SCN)₃] mit Nitrobenzol extrahiert. Die orangerote Lösung hat ihr Absorptionsmaximum bei 470 nm; die molare Extinktion beträgt 18 000±200. Bis 5g Mo/ml entspricht die Lösung dem Beerschen Gesetz. Cu(II), Fe(III), Ti(IV) und W(VI) stören, doch läßt sich diese Störung beseitigen.

     

Extractive spectrophotometric determination of molybdenum as a thiocyanate-2-acetylpyridinethiosemicarbazone complex

A new spectrophotometric method for the determination of molybdenum is based on the extraction of the orange red molybdenum thiocyanate-2-acetylpyridinethiosemicarbazone complex into chloroform from hydrochloric acid. The complex has an absorption maximum at 470 nm with a molar absorptivity of 1.7 × 10⁴ liters mol^?1 cm^?1. Beer's law is valid from 0.1 to 6.5 ppm of molybdenum. The equilibrium shift method indicated a 1:4:2 complex. The method has been used successfully for the determination of molybdenum in molybdenum steels.     

Spectrophotometric determination of molybdenum as a mixed thiocyanate-monooctyl α-anilinobenzylphosphonate complex

A sensitive method for the spectrophotometric determination of molybdenum is described. Molybdenum is reduced with ascorbic acid in hydrochloric acid solution, and complexed with thiocyanate ions, and the complex formed is extracted with monooctyl α-anilinobenzylphosphonate (MOABP) in chloroform. The molar absorptivity of the method is 5858 l mole^-1 cm^-1 at 470 nm. Beer's law is obeyed in the range 0.7–28 μg Mo ml^-1. Few metals interfere; the separation of the interfering elements is discussed. The composition of the extracted complex is Mo(SCN)₅·3 MOABP.     

Extraction-photometric determination of molybdenum as a mixed-ligand complex with 2-hydroxy-5-chlorothiophenol and diphenylguanidine

The complexation of molybdenum with 2-hydroxy-5-chlorothiophenol (HCTP) in the presence of diphenylguanidine (DPG) was studied. The best conditions for the complex formation and extraction were determined. It was found that a mixed-ligand complex was formed in 2–4 M HC1. The best extractant was chloroform. The molar absorptivity of the mixed-ligand complex was found to be 2.5 x 10⁴ (595 nm). The formation of a mixed-ligand complex of the composition Mo(V) : HCTP : DPG =1: 2 : 2 was shown.