Determination of thiuram disulphides and analysis of thiuram disulphide-dithiocarbamate mixtures

Potassium trithiocarbonate is used as reluctant for the titrimetric determination of thiuram disulphides in dimethylformamide-water media. The method is based on reductive cleavage of the disulphide linkage to yield the corresponding dithiocarbamates. In visual titrations, the end-point is marked by appearance of a yellow colour with the first drop of reagent added in excess. The method is simple, accurate, reliable and of wide applicability. It has been successfully extended to the analysis, in the same sample solution, of thiuram disulphide-dithiocarbamate mixtures.     

Determination of microgram amounts of thiuram disulphides by means of the induced iodine-azide reaction

A simple method for the determination of thiuram disulphides was developed. These compounds induce the iodine-azide reaction after cleavage of the SS bond. The consumption of iodine in this reaction is proportional to the amount of the inductor. Inducing properties of the compounds examined were estimated from an induction coefficient ([I]/[S]) which indicates how many times the consumption of iodine in the induced reaction is higher than that in the iodimetric reaction. Under analytically optimum conditions the induction coefficients are in the range 176–211 for eight thiuram disulphides. The identical behaviour of thiuram disulphides in the induced reaction and of the corresponding dithiocarbamates allows the analysis of their mixture in the same sample. The method is sensitive, selective, accurate, cheap and rapid. Other compounds that induce the iodine-azide reaction interfere.     

Volumetric determination of tetraalkyl thiuram disulphides

Summary A method for the volumetric determination of tetraalkyl thiuram disulphide is developed. It is based on its reaction with potassium cyanide in aqueous acetonitrile medium, when the corresponding tetraalkyl thiuram monosulphide and thiocyanate are formed. The former is removed by extraction with benzene and the latter converted into cyanogen bromide, which is estimated iodometrically.

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Zusammenfassung Ein Verfahren zur volumetrischen Bestimmung von Tetraalkyl-thiuramdisulfid wird beschrieben. Es beruht auf der Reaktion mit Kaliumcyanid in wäßriger Acetonitrillösung, wobei das entsprechende Tetraalkyl-thiurammonosulfid und Thiocyanat gebildet werden. Ersteres wird durch Extraktion mit Benzol entfernt; das Thiocyanat wird in Bromcyan umgewandelt, das dann jodometrisch bestimmt wird.

     

Determination of uranium and plutonium in plutonium based fuels by sequential amperometric titration

A method is described for the sequential determination of uranium and plutonium in plutonium bearing fuel materials. Uranium and plutonium are reduced to U(IV) and Pu(III) with titanous chloride and then titrated with dichromate to two end points which are detected amperometrically using two polarized platinum electrodes. Uranium-plutonium solutions of known concentrations containing plutonium in the proportions of 4, 30, 50, and 70% were analyzed with precisions better than 0.3%, maintaining the amounts of plutonium per aliquot in the range of 2–10 mg. No significant bias could be detected. Several samples of (U, Pu)O₂ and (U, Pu)C were analyzed by this procedure. The effects of iron, fluoride, oxalic acid and mellitic acid on the method were also studied.     

Determination of EDTA by catalytic amperometric and catalytic potentiometric titration at a small constant current

Summary Amperometric and potentiometric methods at a small constant current were developed to follow the course of catalytic titrations. In ammoniacal medium EDTA was determined by titration with 0.1 M copper(II) chloride in the presence of hydrogen peroxide as the indicator. Amounts of 42.26–126.87 mg of EDTA were determined with a maximal average deviation of 0.55 %. The results obtained are in good agreement with those of comparable methods.

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Bestimmung von ÄDTA mit Hilfe der katalytischen amperometrischen und der katalytischen potentiometrischen Titration bei kleinem konstantem Strom

Zusammenfassung Die amperometrische und die potentiometrische Methode bei kleinem konstantem Strom wurden für die Verfolgung katalytischer Titrationen ausgearbeitet. ÄDTA wurde in Ammoniakmedium mit 0,1 M Kupfer(II)-chlorid in Anwesenheit von Wasserstoffperoxid als Indicator titriert. Mengen von 42,26–126,87 mg ÄDTA wurden mit einer mittleren Abweichung von 0,55% bestimmt. Die Ergebnisse stimmen gut mit denen vergleichbarer Methoden überein.

The authors thank the SIZ for researchs of SAP Vojvodina for the partial financial support of the present work.     

Determination of proteins by amperometric titration with 12-phosphotungstic acid at rotating gold electrodes

Amperometric titration of various protein fractions and human serum with 12-phosphotungstic acid at the rotating gold electrode is described. The titrant is electroreducible and its concentration may be monitored by poising an amperometric indicator electrode at a potential of -0.25 V vs. SCE. In 1.0 M hydrochloric acid, well defined titration curves of proteins may be obtained in the presence of airsaturated solutions. The relative standard deviation of replicate samples is 0.2–0.3% in the range 2–4 g of protein per 1 in the sample solution. The technique is principally applicable to homogeneous mixtures of proteins.     

Determination of submillimolar concentration of ferrate(VI) in alkaline solutions by amperometric titration

A new amperometric titration method was developed for quantitative determination of ferrate(VI) (Fe^VIO₄ ²⁻) in the 7.06×10⁻⁵−5.73×10⁻³ M concentration range. Chromium(III) hydroxide solution was used as the titrant. The diffusion current (Id) had a linear relationship with the concentration of ferrate(VI) and slopes were dependent on the concentration of NaOH. The amperometric titration could detect a lower concentration of ferrate(VI) than could potentiometric and colorimetric titrations. The method was applied successfully to determine concentrations of ferrate(VI), generated electrochemically, in strong alkaline solutions.      

Preconcentration of trace metals from salt solutions using thiuram disulphide as collector

Traces of Fe, Co, Ni, Cu, Zn, Cd and Pb in salt solutions (e.g. KCl, Ca(NO₃)₂, A1₂(SO₄)₃, Cr₂(SO₄)₃, (NH₄)₂SO₄) are determined by flame AAS after preconcentration with thiuram disulphide (TDS) as collector precipitate. The preconcentration recovery is mainly influenced by pH, TDS amount and its aging in the sample solution. Conditions of an optimal preconcentration procedure were elaborated. Detection limits vary from 0.5 ng/ml (for Cd) to 8.3 ng/ml (for Pb) and the relative standard deviation is 2 to 6 %. The accuracy of the results was checked by differential pulse anodic stripping voltammetry and by electrothermal AAS.     

Determination of colloidal electrolytes: amperometric titration of dodecylquinolinium bromide with inorganic anions

The possibilities of the amperometric titration of aqueous solutions of dodecylquinolinium bromide in 0.1 mol dm^?3 potassium bromide as supporting electrolyte with potassium dichromate, potassium hexacyanoferrate(III) and ammonium molybdate were investigated. Titrations were carried out in which dichromate, hexacyanoferrate(III) and molybdate anions were determined by titration of colloidal electrolyte solutions.     

Electrometric indicators in the amperometric titration of cations and acids

Amperometric titration is carried out at zero potential in the presence of hydroquinone and p-aminophenol as electrometric indicators. Solutions of sodium carbonate, sodium arsenite, sodium tetraborate and potassium cyanide have been used as reagents in neutralisation, precipitation and complex formation reactions for the determination of cations separately, the simultaneous determination of several cations in one sample and of acid and cations present simultaneously. After the equivalence point has been reached, hydroxyl ions appear in the solution as a result of salt hydrolysis and a considerable increase in the current voltage occurs. The indicator in alkaline solution induces the depolarisation of the electrode.     

Determination of neptunium by redox titration

A simple and quick method for the potentiometric determination of neptunium on the 2-5 mg scale has been developed. It consists of oxidation to Np(VI) by AgO or fuming with HClO(4), destruction of excess of AgO by sulphamic acid, reduction of Np(VI) to Np(IV) with a slight excess of standard Fe(II) in 2M H(2)SO(4) and potentiometric titration of the excess of Fe(II) with standard Ce(IV). The precision is +/-0.5%.     

Determination of sulphate by pH titration

A simple and inexpensive method has been developed for the determination of sulphate and other very weak bases and acids. It utilizes the partial protonation of the weak base or the partial dissociation of the weak acid, which has not been exploited for analytical purposes thus far. The procedure consists of three pH titrations: one with a test solution of known sulphate content, the second with the sulphate sample, and the third with a blank. This method can be used in the presence of several inorganic ions and organic matrices, including non-aqueous solvents. In aqueous medium sulphate contents above 10(-3)M can be determined. The use of solvent mixtures may increase the sensitivity of the method by two orders of magnitude.     

Determination of tungsten by acidimetric titration

A new method is described for the acidimetrie titration of tungstate, based on the reaction (x)WO(4)(2-) + xH(+) + mannitol = complex. Quantities of tungsten greater than 2.5 mmole may be determined with a relative standard deviation of not more than 0.1 %. The method is subject to interference by any species in the tungstate solution which absorbs protons in the pH range 5.5-8.5.     

用溶出安培滴定法研究汞中金属互化物

本文提出以溶出安培滴定法测定汞中金属互化物的理论与方法,测得铜锌互化物的组成为Cu:Zn=1:1,铜铊互化物的组成为Cu~3Hg~4:TlHg~6=1:1,其条件生成常数的对数值为8.27和6.43。     

A contribution to the theory of accelerated sulphur vulcanization of natural rubber and polybutadiene BR with tetramethyl thiuram disulphide and bis(2-benzothiazolyl) disulphide

A number of simple natural rubber (NR) and polybutadiene (BR) formulations were vulcanized in a differential scanning calorimeter. From the shapes of the exothermal cure curves the interaction of curatives can be examined. It is suggested that polysulphidic-accelerator-terminated pendent groups could either crosslink, or be chelated with zinc ions. The latter reaction allows interaction with accelerator molecules to reform the unchelated pendent group, and a zinc accelerator complex, that, in turn, can react with sulphur and rubber molecules to give pendent groups. Differences in the behavior of NR and BR are attributed to the relative rates of these two reactions in the elastomers. Bis(2-benzothiazolyl) disulphide does not react with zinc, and it is suggested that it coordinates with the zinc dithiolate accelerator complex, increasing its activity.     

Determination of adenine,caffeine, theophylline and theobromine by HPLC with amperometric detection

A relatively simple method for quantifying caffeine, theobromine, theophylline and adenine by HPLC with amperometric detection was developed. A C₁₈-column and an isocratic elution with phosphate buffer pH 3.5/methanol (90 : 10) were employed for the chromatographic separation of the investigated compounds. The optimal detection potential was +1.4 V. The limits of detection were 0.4 ng for adenine, 1 ng for theophylline and 2.5 ng for caffeine and theobromine. The method was applied to the determination of these purine alkaloids in beverages, tea, coffee and cacao. The determination was carried out directly or after solid-phase extraction.     

Determination of protonation constants by coulometric titration

Application of coulometric titration to the determination of the protonation constants of acids and bases offers several advantages because of its simplicity, precision and accuracy. This procedure is rapid and requires only one calibration solution of strong acid in the same solvent and at the same ionic strength as the solution of acid (or base) being investigated. The procedure seems to be especially advantageous in the case of non-aqueous or mixed solvents having amphiprotic character. The validity of the method has been checked with several substances in water, 95% ethanol and ethylene glycol.     

Determination of lanthanum by flame photometric titration

The flame emission of lanthanum at 560 mmu decreases linearly with phosphate concentration until a 1:1 molar ratio is reached, and then remains practically constant. Lanthanum can be titrated with phosphate, the equivalence point being detected from the change in emission intensity. Errors due to consumption of solution by the atomizer can be kept low by using short spraying times and low galvanometer damping. The average error is about -1% for 0.1M solutions and less than -5% for 0.01M. The method gives good results in the presence of titanium(III), zirconium, thorium and aluminium but cerium(III) and yttrium seriously interfere.     

Studies on analytical methods by amperometric titration using a rotating platinum electrode: Part 47. Successive Determination of L-Cysteine and L-Cystine by Amperometric Titration

The successive determination of {spl}-cysteine and {spl}-cystine (2–5 μmol of each) in mixtures is achieved by amperometric titration with standard potassium iodate solution using a rotating platinum wire electrode at + 0.6 V vs. SCE. {spl}-Cysteine is titrated in acidic bromide-containing solution; sodium chloride (15 g) is then added and the titration is continued to determine L-cystine.