Substoichiometric determination of selenium with potassium ethyl xanthate

A substoichiometric radiochemical method has been developed for the determination of selenium with potassium ethyl xanthate. The selenium ethyl xanthate complex formed was extracted into chloroform from borate buffer at pH 5. The effect of foreign ions on the extraction was studied. Microgram quantities of selenium could be conveniently determined with a fair degree of accuracy. The method has been successfully applied for the determination of selenium content in food stuffs such as Jaggery and Wheat powder.     

Spectrophotometric determination of selenium in concentrates and high-purity copper metal with 3,3'-diaminobenzidine after separation by xanthate extraction

A method for determining 0.0001-0.10% of selenium in copper, nickel, molybdenum, lead and zinc sulphide concentrates is described. After sample decomposition, selenium is reduced to the quadrivalent state by heating in a 4M hydrochloric acid-5M sulphuric acid medium, then extracted into chloroform as the xanthate, and ultimately determined spectrophotometrically with 3,3'-diaminobenzidine. Small amounts of iron, lead and copper, and an appreciable amount of molybdenum are co-extracted as xanthates but do not interfere. More than 5 mg of antimony will cause low results. The proposed method was developed primarily for concentrates, but it is also applicable to high-purity copper.     

Substoichiometric radiochemical determination of silver with potassium ethyl xanthate in photofilm washings

An accurate and rapid radiochemical method has been developed for the determination of microgram amount of silver employing potassium ethyl xanthate as a substoichiometric radiochemical reagent. The light yellow coloured silver ethyl xanthate formed was extracted into nitrobenzene from sulphuric acid media. The effect of foreign ions on the extraction was studied. The method was applied to the determination of silver content in photofilm washings.     

Capillary electrophoretic determination of dithiocarbamates and ethyl xanthate

A simple and sensitive capillary electrophoretic method was developed for the separation and determination of sodium methyldithiocarbamate (metham), manganese ethylenebisdithiocarbamate (maneb) and ethyl xanthate in boric acid buffer by direct UV absorbance detection at lambda = 254 nm. The separation is dependent on pH and nature of the buffer. The detection limits (S/N = 3) are 1.7 x 10(-6) mol/L for ethyl xanthate, 1.3 x 10(-6) mol/L for metham and 2.1 x 10(-6) mol/L for maneb. The method has been successfully applied to the analysis of wheat samples spiked with maneb and in a commercial sample.     

Determination of selenium content of animal food-stuff using photon activation analysis

Photon activation analysis has been developed to determine the selenium content. The method can be applied for continuous monitoring of the addition of selenium to animal food-stuff.     

Capillary electrophoretic determination of dithiocarbamates and ethyl xanthate

A simple and sensitive capillary electrophoretic method was developed for the separation and determination of sodium methyldithiocarbamate (metham), manganese ethylenebisdithiocarbamate (maneb) and ethyl xanthate in boric acid buffer by direct UV absorbance detection at λ = 254 nm. The separation is dependent on pH and nature of the buffer. The detection limits (S/N = 3) are 1.7 × 10^–6 mol/L for ethyl xanthate, 1.3 × 10^–6 mol/L for metham and 2.1 × 10^–6 mol/L for maneb. The method has been successfully applied to the analysis of wheat samples spiked with maneb and in a commercial sample.     

Determination of trace amounts of the flotation collectors ethyl xanthate and diethyl dithiophosphate in aqueous solutions by cathodic stripping voltammetry

A cathodic stripping method has been devised for determination of low concentrations of the flotation collectors ethyl xanthate, diethyl dixanthogen and diethyl dithiophosphate. The limit of detection for ethyl xanthate was 1 x 10(-8)M by the differential pulse technique and with deposition for 2 min at -0.1 V. Three peaks were observed, each increasing in different concentration ranges of ethyl xanthate. A reaction mechanism is proposed. The detection limit for diethyl dithiophosphate was 1 x 10(-7)M by the differential pulse technique and with deposition for 3 min at -0.1 V. The analytical method was applied to determine ethyl xanthate in a sulphide mineral flotation plant and the amount of adsorbed ethyl xanthate and diethyl dithiophosphate on Cu(2)S. It was found that the adsorbed ethyl xanthate forms nearly a monolayer on Cu(2)S and that the amount of adsorbed diethyl dithiophosphate corresponds approximately to 0.4 monolayer.     

Comparative substoichiometric extraction and quantification of mercury in geological water samples with potassium salts of ethyl,propyl, butyl,pentyl and benzyl xanthates

The relative extent of extraction of mercury with potassium salts of ethyl, propyl, butyl, pentyl and benzyl xanthates has been studied employing a sensitive and rapid substoichiometric radiochemical method. The effect of pH on the extractability of mercury xanthate complexes into chloroform was investigated. Buffer solutions of pH 12, 11, 10, 9 and 5.5 were found to be suitable media for the maximum extraction of mercury as ethyl, propyl, butyl, pentyl and benzyl xanthate complexes, respectively. The procedures developed were utilized for the determination of mercury content in standard solutions and geological water samples collected in eight parts of Chittoor district of Andhra Pradesh.     

Determination of cadmium in water samples by substoichiometric radiochemical method employing potassium ethyl xanthate

A radiochemical method has been developed for the determination of microgram amounts of cadmium based on the substoichiometric extraction of its 1:2 complex with potassium ethyl xanthate into 1:4 v/v mixture of pyridine and ethyl acetate from 2.5 M sodium formate. 10-90 micrograms of cadmium was determined with an average error of +/- 1.96%. The method developed was successfully applied to the determination of Cd contents in water samples.     

Rapid radiochemical separations in neutron activation analysis using ion retention media

A rapid radiochemical procedure based on the removal of mercury, selenium, arsenic and antimony by columns of C₁₈-bonded silica gel or activated carbon after their selective complexation in sulphate/nitrate media by ammonium pyrrolidine-dithiocarbamate, diethylammonium diethyldithiocarbamate, potassium ethyl xanthate, bismuthiol II or 8-hydroxyquinoline, was examined. Comparisons were made of the ability of the two ion retention media to remove these metal ions and to allow their regeneration and recycling. The effectiveness of this technique was demonstrated by analysis of horse kidney and human diet, International Atomic Energy Agency biological reference materials, for mercury and selenium.     

Coprecipitative Preconcentration and Differential Pulse Cathodic Stripping Voltammetric Determination of Selenium (IV)

Abstract

A DPCSV procedure for the determination of selenium (IV) with a prior preconcentrative coprecipitation on iron (III) hydroxide has been developed. The experimental conditions for coprecipitation of selenium (IV) onto iron (III) hydroxide, viz. pH, iron (III) concentration, volume of aqueous phase and selenium concentration, were optimized. The coprecipitated selenium (IV) is dissolved in 10 ml of 0.1 M HCl and analysed using DPCSV in the presence of copper (II). Selenium concentrations as low as 10–100 ng present in 500 ml of the aqueous phase could be determined. The method is precise and has been applied to the analysis of sea water and reference material samples.     

Dithiocarbamate extraction of trace amounts of selenium from biological samples for neutron activation analysis

A three-step method has been developed for extracting trace amounts of selenium from biological samples for neutron activation analysis /NAA/. After acid digestion, the sample is first extracted with lead diethyldithiocarbamate at pH 4 to remove a number of interfering elements. Next, selenium is extracted with sodium diethyldithiocarbamate into chloroform at pH 1.5. Finally, selenium is back-extracted with concentrated nitric acid for NAA. Analysis of selenium extracted from four standard reference materials resulted in excellent agreement with the certified values of selenium concentration. A detection limit of 0.05 g has been achieved.     

A Novel Method for Analysis of Xanthate Group Distribution in Viscoses

Analytical monitoring of xanthation in the viscose process along with xanthate group analysis in the viscose material is a long-debated problem in cellulose chemistry. The task is rendered extremely intricate by the lability of the starting material and the harshness of the reaction medium, which adds to a lack of suitable analytical approaches. In a four-years' endeavor in our lab, a method is being developed which allows to analyze the distribution of xanthate groups in viscoses relative to the anhydroglucose units and along the cellulose chain. In a first step the xanthate groups are stabilized by alkylation, which was optimized towards quantitative conversion. In a second step, the remaining free hydroxyl groups are protected by carbanilation, followed by selective removal of the stabilized xanthate groups. Steps two and three thus generate an inverse image of the initial xanthate pattern. In the forth and fifth step, the liberated hydroxyl groups are methylated, and the carbanilates are removed, so that in the overall process the xanthates were replaced by methyl groups. All reaction steps have been comprehensively tested with regard to completeness of conversion and orthogonality of the protecting groups.     

Reduction and determination of dixanthogens

A convenient method for the reduction and determination of dixaathogen has been developed. It is based on the quantitative reaction of dixanthogen with zinc amalgam to form xanthate; the latter can be determined by iodine titration, potentiometric titration with silver nitrate or by spectrophotometry at 310 mmu. Dixanthogen can be determined in mixtures containing xanthate, by titration of aliquots with and without reduction. Higher dixanthogens can also be determined, and flotation liquors analysed.     

Activation analysis by internal conversion electron spectra

The applicability of instrumental activation analysis by the conversion radiation of impurities in matrices with high specific gamma-activity has been studied. An iron-free toroidal magnetic β-spectrometer with 2 per cent resolution and 20 per cent transmission for 4 was used for measurement. The spectrometer was made at the Activation Analysis Laboratory of the Academy of Sciences of the Kazakh SSR. Comparative gamma- and beta-spectra of samples of amorphous selenium thin films with palladium, cadmium, indium and mercury impurities were obtained. It was established that the analysis by the spectra of internal conversion electrons enables to increase the detection sensitivity of these elements in selenium as compared to the gamma-spectrometric method. The procedure of mercury determination in amorphous selenium films was developed and by this method the investigation of the dependence of photoconductive properties of the film upon the total mercury content and its distribution on the film surface was carried out.     

Spectrophotometric determination of cobalt, nickel, palladium, copper, ruthenium and molybdenum after extraction of their isoamyl xanthate complexes into molten naphthalene

A method has been developed for the spectrophotometric determination of microamounts of Co(II), Ni(II), Cu(II), Pd(II), Ru(III) and Mo(VI) after extraction of their isoamyl xanthate complexes into molten naphthalene. The method has been applied to the determination of these metal ions in various alloys and in environmental samples (fly ash).     

Microdetermination of Xanthates

Summary A rapid, convenient and accurate method for the determination of xanthates has been developed. N-bromosuccinimide has been used to displace iodine from potassium iodide which in turn oxidizes xanthate to dixanthogen. The p_H 4 is optimum for the determination. The maximum relative standard deviation is 6% in the case of ethyl potassium xanthate when a 0.5 mg sample was taken.

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Zusammenfassung Ein genaues Verfahren zur raschen Bestimmung von Xanthat wurde entwickelt. N-Bromsuccinimid dient zur Freisetzung von Jod aus KJ; Jod oxydiert Xanthat zu Dixanthogen. Das optimale p_H für die Bestimmung ist 4. Die größte relative Standardabweichung ist 6% bei einer Einwaage von 0,5 mg Kaliumäthylxanthat.

     

Determination of the xanthate group distribution on viscose by liquid-state <Superscript>1</Superscript>H NMR spectroscopy

An analytical method for determination of the xanthate group distribution on viscoses based on liquid-state NMR spectroscopy was developed. Sample preparation involves stabilization of the xanthate group by allylation followed by derivatization of the remaining free hydroxyl groups at the glucose unit. The method was applied for studying (1) the γ-value (number of xanthate groups per 100 glucose units) of viscose, (2) the distribution of the xanthate groups on the anhydroglucose unit (AGU), and (3) changes of the xanthate group distribution during ripening. Results of the γ-value determination are well comparable with reference methods. Elucidation of the xanthate group distribution on the AGU gives the percentage at the C-6 position and a cumulative share of the positions C-2 and C-3. During ripening, xanthate groups at C-2 and C-3 degrade first, while xanthates at C-6 decompose at a slower rate.     

An indirect atomic-absorption method for the determination of selenium

Because of the difficulty in determining selenium directly, an indirect atomic-absorption method has been developed, based on two selective reactions that lead to the formation of the Pd(DanSe)(2)Cl(2) complex and measurement of the palladium absorption. Reaction conditions, separation techniques, effect of foreign ions, instrumental conditions and sample analysis in the sub-ppm range are described. The method is more sensitive than existing atomic-absorption methods for selenium.     

Highly Sensitive Determination of Butyl Xanthate in Surface and Drinking Water by Headspace Gas Chromatography with Electron Capture Detector

A highly sensitive and convenient method for the determination of butyl xanthate in surface water and drinking water was developed by headspace gas chromatography with electron capture detector (HS–GC–ECD). The analytical method was based on the decomposition of butyl xanthate under an acidic condition, generating carbon disulfide, which could be sensitively detected by gas chromatography with electron capture detector. The signal of CS₂ from the decomposition of potassium butyl xanthate was directly proportional to the concentration of potassium butyl xanthate over the range 0.7–100 ng/mL. The detection limit at a signal-to-noise ratio of three (S/N = 3) for potassium butyl xanthate was 0.3 ng/mL (~1.6 × 10⁻⁹ mol/L), which was more than two orders of magnitude lower than the popular UV methods and close to one order of magnitude lower than the similar headspace gas chromatography–mass spectroscopy method. The relative standard deviation (R.S.D.) within a day and in 3 days for potassium butyl xanthate at both 5 and 50 ng/mL was less than 4.7 %, suggesting good analytical performance of the present method. Good recoveries from 93.3 to 104.7 % were obtained from spiked surface and drinking water samples, indicating that the proposed HS–GC–ECD method was applicable for the quantification of butyl xanthate in surface and drinking water. Compared with other reported methods, the present method is highly sensitive, without sample preparation, and easily extended to the analysis of other xanthates.