Spectrophotometric determination of anions by reextraction through the exchange of ligands: The determination of traces of oxalate using ferric indol-2-carboxylate in isoamyl alcohol

In this paper an indirect spectrophotometric method is proposed to determine oxalate, by a new technique called “reextraction through the exchange of ligands.” This new method is based on the decoloration produced in organic solutions of colored complexes when mixed with aqueous solutions of complexing anions.The established procedure for the preparation of solutions of ferric indole-2-carboxylate in isoamyl alcohol is given, as well as a discussion of the variables which influence the reextraction through the exchange of ligands.Finally, the technique was applied in determining traces of oxalate in an aqueous solution. The decoloration varies linearly with the oxalate concentration between 1 and 6 ppm. The error and reproducibility of the method were calculated. Also studied were the value of the constant of exchange and the interferences caused by various ions.     

Quinone—cyanide reactions: their use for the determination of quinones and cyanide

Both quinones and cyanide can be determined in the μg—ng ml^-1 range by measuring the fluorescence of the addition products produced. The yield is low (except for the 2-sulfonic acid of 1,4-naphthoquinone) in aqueous solution and 1:1 DMSO:water is the recommended medium for determinations of quinones. The 2-sulfonic acid of 1,4-naphthoquinone permits the determination of trace amounts of cyanide in aqueous solution; there are few interferences.     

Continuous spectrophotometric determination of copper, nickel and zinc in copper-base alloys by flow-injection analysis

Flow-injection methods have been developed for the determination of copper, nickel and zinc in copper-base alloys, including several types of brasses, deoxidized copper, beryllium copper and German silver. The system for copper and nickel involves the measurement of the absorbance of the copper(II) and nickel(II) aquo-complexes at 805 and 410 nm, respectively, after simple dissolution of the sample in a nitric acid-phosphoric acid mixture. The system needs no further reagents and the sample solutions can be analysed at rates of up to 280 /hr for copper (or nickel in German silver) without any carry-over. The system for zinc consists of automatic dilution of the injected sample with a thiosulphate-acetate buffer solution and the subsequent measurement of the absorbance of the zinc-Xylenol Orange complex at 568 nm. This system permits analysis rates of up to 90/hr for zinc solutions, with no carry-over. The procedures have been applied to standard copper-base alloys. The results agreed satisfactorily with the certified values. The precision ranges are 0.2-0.7% for copper and nickel and 0.5-0.8% for zinc.     

A flame spectrophotometric method for the determination of nickel and boron in plating solutions

The flame photometric method as a rapid means of estimating the nickel and boron concentrations in nickel plating solutions is described. The effect of methanol concentration upon the flame emission of the 352.5 mμ nickel line in 1 to 1 methanol—water solution was studied. The effect of nickel concentration upon the flame emission of boron in 1 to 1 methanol —water solution was studied for the oxide band system at 518 mμ.On étudie l'effet de la concentration du méthanol sur la flamme d'émission de la raie 352.5 mμ du nickel dans un mélange eau —méthanol 1:1.L'effet de la concentration en nickel sur la flamme d'émission du bore dans un mélange eau —mé -thanol 1:1 est étudié pour les bandes de l'oxyde á 518 mμ     

The study of decomposition reactions through the exchange of thermal energy

In many decomposition reactions, the reaction velocity can be described as a product of two functions: a temperature dependent part K(T) and the kinetic function f(1 – α), where T designates the temperature and α the fraction of reactant that has decomposed. The physical interpretation of these functions is discussed for both solid and homogeneous systems. A method is described by which f(1 – α) and K(T) can be determined from kinetic data. The mechanism of decomposition can subsequently be identified which should be consistent with the derived kinetic parameters. The method has been applied to analyze the kinetics of the thermal decomposition of nitromethane. © 1994 John Wiley & Sons, Inc.     

Use of 3-hydroxy-1,3-diphenyltriazine in the spectrophotometric determination of copper, palladium, iron, cobalt, nickel, and molybdenum

3-Hydroxy-1,3-diphenyltriazine (HDPTA) forms brightly coloured complexes with copper, palladium, iron, cobalt and nickel ions, which are readily extractable in benzene. The deep yellow molybdenum complex is completely soluble in 60% ethanol. All the chelates have a definite absorption maximum between 398 and 422 nm, the reagent absorption being negligible above 415 nm. The molar composition of the chelates is ML(2), except for iron and cobalt which form ML(3) complexes. Microquantities of these metals can be determined spectrophotometrically with HDPTA.     

The reactions of pentacyanoferrate(II) ions-iv spectrophotometric study, detection and determination of Toxogonine

The interaction of Toxogonine with ammine- and nitrosyl-pentacyanoferrate(II) ions has been studied spectrophotometrically under different reaction conditions. The same reactions were the basis for specific spot-tests and new simple and rapid spectrophotometric methods for the determination of Toxogonine in the range 15-85 or 15-150 mug/ml. From the calibration curves the molar absorptivities of the complexes were calculated and the proposed methods tested for the determination of Toxogonine in pharmaceutical preparations.     

The determination of aluminum,nickel, cobalt,copper, and iron in alnico

A method has been developed for the determination of the major constituents of Alnico based on an anion exchange separation of the chloride complexes and the subsequent determination of aluminum, nickel, copper, cobalt and iron with EDTA. The method is more convenient than conventional classical methods.     

Liquid-liquid extraction of ferric thiocyanate with hexamethyl phosphoramide: Direct spectrophotometric determination in the organic phase

Summary Application of hexamethylphosphoramide (HMPA) in the iron(III)-thiocyanate system gives a simple, sensitive and highly selective method for the spectrophotometric determination of Fe(III) in the organic phase (CHCl₃). The color is stable for more than 24 hours in CHCl₃. The system obeys Beer's law for 7g Fe/ml and the optimum concentration range is found to be 0.5–5g/ml. The molar absorptivity of 1.33×10⁴ l·mole^–1·cm^–1, and Sandell's sensitivity is 0.0044/cm² at 460 nm The composition of Fe(III) to thiocyanate is found to be 13 in the presence of HMPA in CHCl₃. The method is free from interferences of many anions and cations. The method has been used to determine iron in bauxite ore.

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Flüssig-flüssig-Extraktion von Eisenrhodanid nach Zusatz von Hexatnethyl-pbosphoramid: Direkte spektrophotometrische Bestimmung in der organischen Phase

Zusammenfassung Der Zusatz von Hexamethylphosphoramid (HMPA) zu Eisen(III)-Thiocyanat führt zu einer einfachen, empfindlichen und sehr selektiven Methode der spektrophotometrischen Bestimmung von Fe(III) in organischer Phase (CHCl₃). Die Farbe bleibt in Chloroform mehr als 24 Stunden beständig. Das System entspricht dem Beerschen Gesetz unterhalb 7g Fe/ml. Das Konzentrationsoptimum liegt zwischen 0,5 und 5g/ml. Die molare Extinktion beträgt 1,33·10⁴ l·Mol^–1·cm^–1, die Empfindlichkeit nach Sandell 0,0044g/cm² bei 460 nm. Das Verhältnis Fe(III): Rhodanid in CHCl₃ ist 13 in Gegenwart von HMPA. Die Methode wird von vielen Anionen und Kationen nicht gestört. Sie wurde zur Bestimmung von Eisen in Bauxit verwendet.

     

The gravimetric determination of nickel with dimethylglyoxime in the presence of copper

Summary A detailed investigation has been made of the gravimetric determination of nickel with dimethylglyoxime in the presence of copper. Copper interference is eliminated by precipitation in a solution containing tartrate and thiosulphate at a p_H of 5.5–6.5. The solubility of the nickel dimethylglyoxime complex has been determined as a function of temperature, p_H and alcohol concentration.     

A comparative study of radioactivation,atomic absorption and spectrophotometric techniques applied to the determination of mercury in lead

A fairly simple radiometric method has been developed for the quantitation of microgram amounts of mercury in lead samples of different purity grades. It is mainly based on 3 steps; (i) the removal of most interfering cations with ferric hydroxide scavenger in the presence of a suitable masking agent, (ii) the separation of mercury as hydrated mercuric oxide from a highly alkaline medium, (iii) its distillation as mercuric chloride followed by precipitation as the sulfide. The method is reproducible and the results which show, in general, a standard deviation of ±4.29% are compared with those obtained by atomic absorption (4.48%) and spectrophotometric (13.13%) techniques.     

Electrothermal atomic absorption spectrometric determination of cobalt, copper, lead and nickel traces in aragonite following flotation and extraction separation

A method of determination of Co, Cu, Pb and Ni in nanogram quantities from aragonite is presented. Flotation and extraction of Co, Cu, Pb and Ni is suggested as methods for elimination matrix interferences of calcium. The method of flotation is performed by iron(III) hexamethylenedithiocarbamate, Fe(HMDTC)(3), as a colloid precipitate collector. The liquid-liquid extraction of Co, Cu, Pb and Ni is carried out by sodium diethyldithiocarbamate, NaDDTC, as complexing reagent into methylisobutyl ketone, MIBK. The electrothermal atomic absorption spectrometry (ETAAS) is used for determination of analytes. The detection limits of ETAAS followed by flotation are: 7.8 ng.g(-1) for Co, 17.1 ng.g(-1) for Cu, 7.2 ng.g(-1) for Pb and 9.0 mug.g(-1) for Ni. The detection limits of ETAAS followed by extraction are found to be: 12.0 ng.g(-1) for Co, 51.0 ng.g(-1) for Cu, 24.0 ng.g(-1) for Pb and 21.0 ng.g(-1) for Ni.     

Extraction-spectrophotometric determination of traces of bismuth in lead,copper and nickel metals,and in copper-base alloys with tri-n-octylamine

A rapid and sensitive spectrophotometric method has been developed for the determination of bismuth in lead, copper and nickel metals, and in copper-base alloys. Optimal conditions have been established for the extraction and determination of bismuth. Bismuth is extracted with a benzene solution of tri-n-octylamine in the presence of hydrobromic acid and the absorbance of the extract (bromo-complex of bismuth) at 380 nm is measured. As little as 0.5 p.p.m. of bismuth in these metals and alloys can be determined.     

A rapid spectrophotometric method for the determination of trace level lead using 1,5-diphenylthiocarbazone in aqueous micellar solutions.

A very simple, ultra-sensitive and fairly selective direct spectrophotmetric method is presented for the rapid determination of lead(II) at ultra-trace level using 1,5-diphenylthiocarbazone (dithizone) in micellar media. The presence of the micellar system avoids the previous steps of solvent extraction and reduces the cost and toxicity while enhancing the sensitivity, selectivity and the molar absorptivity. The molar absorptivities of the lead-dithizone complex formed in the presence of the cationic cetyltrimethylammonium bromide (CTAB) surfactants are almost ten times the value observed in the standard method, resulting in an increase in the sensitivity of the method. The reaction is instantaneous and the absorbance remains stable for over 24 h. The average molar absorption coefficient was found to be 3.99 x 10(5) L mol(-1) cm(-1) and Sandell's sensitivity was 30 ng cm(-2) of Pb. Linear calibration graphs were obtained for 0.06-60 mg L(-1) of Pb(II); the stoichiometric composition of the chelate is 1:2 (Pb:dithizone). The interference from over 50 cations, anions and complexing agents has been studied at 1 mg L(-1) of Pb(II). The method was successfully used in the determination of lead in several standard reference materials (alloys and steels), environmental water samples (potable and polluted), biological samples (human blood and urine), soil samples and solutions containing both lead(II) and lead(IV) and complex synthetic mixtures. The method has high precision and accuracy (sigma = +/-0.01 for 0.5 mg L(-1)).     

Spectrophotometric study of cobalt, nickel, copper, zinc, cadmium and lead complexes with murexide in dimethylsulphoxide solution

The complexation reactions between murexide and Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+) ions have been studied spectrophotometrically in dimethylsulphoxide solution at 25 degrees . The stoichiometry of the complexes was found to be 1:1. The stability constants of the complexes were determined, and found to follow the Irving-Williams rule for the cations of the first transition series. In dimethylsulphoxide solution, the complexes are much more stable than those in aqueous solution.     

Molten potassium thiocyanate: The reactions of some compounds of iron,cobalt, nickel,copper and zinc

The electronic spectra of four transition metal cations stable in molten potassium thiocyanate [Fe(II), Co(II), Ni(II) and Cu(I)] are reported together with their reactions and those of three unstable cations [Fe(III), Co(III) and Cu(II)] with a variety of anions including cyanide, cyanate and sulphide. A novel reduction of zinc(II) sulphate is also reported.     

The use of oxalyldihydrazide in a new reaction for the spectrophotometric microdetermination of copper

A new reaction for the spectrophotometric microdetermination of copper is described. To a strongly ammoniacal solution containing traces of copper is added a saturated solution of oxalyldihydrazide and formaldehyde or preferably acetaldehyde. A blue-violet to violet color of unusually high intensity is obtained. The absorbancy maximum is situated at about 542 mμ and the molar absorbancy index has a value of about 29,500 (log? = 4.47). This value is most certainly the highest hitherto known for any copper reagent..The order of addition of the reagents is of great importance. The aldehyde should definitely be added last. The purity of the aldehyde does not seem to be of any great importance for the intensity or stability of the color.     

Simultaneous determination of lead, nickel, tin and copper in aluminium-base alloys using slurry sampling by electrical discharge and multielement ETAAS

The simultaneous multielement determination of Pb, Sn, Ni and Cu in aluminium alloys by electrothermal atomic absorption spectrometry (ETAAS) was performed by a quick method using slurry sampling. The metallic colloidal slurries were obtained by an electrical discharge operated in liquid medium. In this work, the effects of aluminium were evaluated and the results show that it causes a strong retention of Pb, Ni and Cu at low pyrolysis temperatures which is overcome by employing high pyrolysis temperatures. Aluminium also significantly improves the thermal stabilisation of Pb and Sn, it being possible to reach pyrolysis temperatures of 1100 and 1300 °C, respectively. Such stabilisation indicates that the performance of aluminium as a matrix modifier for Pb is better than that obtained using phosphate and magnesium nitrate without substantial changes of the figures of merit. The effects of aluminium on the atomisation characteristics of the elements and those coming from the simultaneous multielement determination on the figures of merit of the elements are also discussed. In this work, a calibration procedure involving a matrix matching method with aqueous aluminium standards is proposed as a simple and efficient way to solve the inconveniences originated by the aluminium matrix. The proposed method was applied to the simultaneous multielement determination of several aluminium-base alloy standards giving results well within the recommended values.     

Measurement of voltammetric peak area and resolution of overlapping peaks in the simultaneous determination of copper, lead, cadmium, and nickel in environmental matrixes

Peak area was used for the simultaneous determination of copper(II), lead(II), cadmium(II), and nickel(II) in environmental matrixes by differential pulse voltammetry. The voltammetric measurements were performed with a conventional 3-electrode cell and an ammonia-ammonium chloride buffer, pH 9.1, as the supporting electrolyte. The analytical procedure was verified first in aqueous reference solutions and later by analysis of the standard reference materials Estuarine Sediment BCR-CRM 277 and River Sediment BCR-CRM 320. The precision and accuracy of the method, expressed as the relative standard deviation and the relative error, respectively, were <5% in all cases; the detection limit for each element under the experimental conditions used was in the range 1-5 microg/L. In the case of mutual interference between neighboring elements, an analytical procedure is proposed that is based on the standard additions technique, which allows the resolution of the overlapping voltammetric peaks.