Indirect spectrophotometric determination of borate using nitron as reagent

An indirect method is outlined for the spectrophotometric determination of small amounts of borate. Borate is quantitatively precipitated as nitron tetrafluoborate in the presence of excess nitron. After separating off the precipitate, the excess of reagent is determined in the supernatant liquid as nitron cobaltothiocyanate.     

Indirect bromometric microdetermination of nitrate and perchlorate,using nitron as reagent

Summary An indirect bromometric method for the determination of nitrate or perchlorate is described. A known excess of standard nitron acetate solution is added to the sample solution to precipitate the anion to be determined; the excess of reagent is then determined in the supernatant liquid by bromatometric titration. The relative standard deviation of the method is 0.7% for nitrate and 0.5% for perchlorate. Sulphate, phosphate and fluoride do not interfere and chloride does not interfere up to a concentration of 0.1 M. Bromide, iodide, chromate, nitrite and chlorate interfere but can be eliminated.

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Zusammenfassung Ein indirektes bromatometrisches Verfahren zur Bestimmung von Nitrat oder Perchlorat wurde beschrieben. Ein gemessener Überschuß einer Nitronacetatlösung bekannter Konzentration wird zur Fällung des Anions der Probe zugesetzt und im Überstand bromatometrisch zurücktitriert. Die rel. Standardabweichung beträgt 0,7% für Nitrat und 0,5% für Perchlorat. Sulfat, Phosphat und Fluorid stören nicht; Chlorid stört nicht bis zu 0,1-m Konzentration. Bromid, Jodid, Chromat, Nitrit und Chlorat stören zwar, können aber eliminiert werden.

     

Use of a nitrate-selective electrode for perrhenate and perchlorate

The nitate-selective membrane electrode based on tributyloctadecylphosphonium nitrate can be used to quantify perrhenate and perchlorate after appropriate conditioning of the membrane. Near-Nernstian responses are obtained for 10^?3–10^?6 M perrhenate and 10^?2–4 × 10^?6 M perchlorate. Iron(II), copper(II) and chloride do not interfere in moderate amounts; other interferences are discussed. Rhenium leaches are analysed after suitable sample preparation. The electrode is useful in following the potentiometric titration of perrhenate with nitron.     

Poly (Vinyl Chloride) Matrix Membrane Electrodes Responsive to Thiocyanate,Perchlorate and Periodate

Abstract

Three types of PVC matrix membrane ion-selective electrodes (ISEs) are described. These are based on membranes containing nitron thiocyanate with 2-nitro-phenyl phenyl ether, 2-nitrophenyl phenyl ether alone and tetraphenylarsonium thiocyanate with 2-nitrophenyl octyl ether. Each type is conditioned and stored in 0.1M sodium thiocyanate. The first two electrodes have been evaluated for thiocyanate and perchlorate response and the best linear long range (linear range down to 2.5×10^?5M) response was obtained for perchlorate. The third electrode is suitable as a periodate ISE with linear calibration range down to 2×10^?4M. The plasticized (2-nitrophenyl phenyl ether) PVC electrode for thiocyanate and perchlorate had a much longer pH interference free range (1.5–12.5) than either of the other electrodes.     

Sequential titrations of anions with cetylpyridinium chloride

Summary The recently reported sequential titration of perchlorate and iodide vs. nitron was critically examined and improved. Some possible sequential titrations of anions vs. cetylpyridinium chloride were examined. Up to four separate endpoint breaks for four groups of anions were obtained. Under optimum conditions, these may be used for the estimation of certain anions or groups of anions.

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Sequentielle Titrationen von Anionen mit Cetylpyridiniumchlorid

     

A new liquid membrane electrode for the selective determination of perrhenate

A new perrhenate ion-selective electrode has been developed, incorporating a nitrobenzene solution of nitron perrhenate as a liquid membrane. The electrode gives near-Nernstian response to 3 x 10(-5)-10(-2)M perrhenate over the pH range 3-8. Most common anions (except for periodate and perchlorate) give little interference. The electrode has been satisfactory for direct potentiometric determination of as little as 10 mu/ml rhenium. The average recovery and standard deviation were 99% and 2.1%, respectively. Measurements of the solubility products of some sparingly soluble perrhenates gave results that agreed closely with those recorded in the literature and obtained by other procedures.     

Analysis of nitrate-perchlorate mixtures by difference spectrophotometry

Nitron and tetraphenylarsonium chloride react with a cobaltous salt in the presence of thiocyanate to form blue ion-association complexes, which can be extracted with organic solvents. This fact has been made the basis for the analysis of mixtures of nitrate and perchlorate by difference spectrophotometry. An aliquot of the sample solution is treated with a known excess of tetraphenylarsonium chloride to precipitate perchlorate only. After separating off the precipitate, the excess of reagent is determined in the supernatant liquid as tetraphenylarsonium cobaltothiocyanate and the perchlorate content can be found from a calibration curve. Another aliquot is treated with an excess of nitron to precipitate both anions; the excess of nitron is then determined as nitron

2. Analysis of Nitrate-Perchlorate Mixtures

     

8.

Infrared spectra for the identification of some inorganic anions using nitron as precipitant     

Robert J. Magee  Salah A. F. Shahine  Cecil L. Wilson 《Mikrochimica acta》1964,52(2-4):479-486

Summary Using infrared absorption spectroscopy a method has been developed which permits the identification, either singly or in admixture, of the following anions: ferrocyanide, ferricyanide, cobalticyanide, chlorate, bromate, perchlorate, periodate, nitrate, nitrite, tungstate, molybdate and chromate. The anions are precipitated by nitron, and using the KBr-disc technique characteristic bands are obtained in the near infrared.

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Zusammenfassung Durch Infrarotabsorptionsspektroskopie lassen sich entweder allein oder in Gemischen folgende Anionen identifizieren: Cyanoferrat(II), Cyanoferrat(III), Cyanokobaltat, Chlorat, Bromat, Perchlorat, Perjodat, Nitrat, Nitrit, Wolframat, Molybdat und Chromat. Die Anionen werden mit Nitron gefällt und geben bei Verwendung einer Kaliumbromid-Linse charakteristische Banden im nahen Infrarot.

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Résumé On a développé une méthode permettant l'identification par spectrographie d'absorption infrarouge des anions suivants, séparément ou en mélanges: ferrocyanure, ferricyanure, cobalticyanure, chlorate, bromate, perchlorate, periodate, nitrate, nitrite, tungstate, molybdate et chromate. On précipite les anions par le nitron et l'on met en évidence les bandes caractéristiques dans l'infrarouge proche, par la technique à la pastille de KBr.

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Dedicated to ProfessorA. A. Benedetti-Pichler on the occasion of his 70th birthday.

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One of us (S. A. E. S.) acknowledges gratefully the award of a scholarship from the U. A. R. Government, which has enabled him to take part in this work.     

9.

Nitron as a titrant in potentiometric determination of nitrate     

Hulanicki A  Maj M 《Talanta》1975,22(9):767-769

A volumetric method of nitrate determination has been developed, using nitron as a titrant and detecting the end-point potentiometrically with a membrane electrode sensitive to nitrate. To get a better insight into the characteristics of the system, the acid dissociation constant of nitron was evaluated spectrophotometrically (pK(a) = 10.34). The solubility product of nitron nitrate was found to be 1.78 +/- 0.03 x 10(-6) (20 degrees , 0.05M K(2)SO(4)). The optimal nitrate concentration for titration is about 0.01M and this method may be successfully applied for determination of nitrate nitrogen in fertilizer samples.     

10.

Association studies of tetramethylguanidinium perchlorate and tetramethylguanidinium chloride in ethanol solutions at 25°C     

O. D. Bonner  Š. Paljk  C. Klofutar 《Journal of solution chemistry》1991,20(5):539-550

Practical osmotic coefficients of ethanol solutions of tetramethylguanidinium perchlorate and tetramethylguanidinium chloride were determined by the isopiestic method at 25°C. The relations for the concentration dependences of practical osmotic coefficients, mean molal activity coefficients of solutes and for the excess Gibbs free energies of solutions and partial molal excess Gibbs free energies of solutes and solvents are given in analytical form. The results obtained are compared with those reported previously; in the case of tetramethylguanidinium perchlorate with its aqueous and methanol solutions, in the case of tetramethylguanidinium chloride with its aqueous solutions. The non-ideal behavior of the systems investigated is discussed on the basis of the structure of solute species, as well as on the nature of the solvent.     

11.

Capillary electrophoresis determination of nitrate and nitrite in high-salt perchlorate solutions for the UC dissolution study     

N. Budanova  B. Fourest  A. Maslennikov 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(3):597-602

The capillary electrophoresis method with direct UV detection is proposed for the determination of nitrite and nitrate in high-salt perchlorate solutions issued from uranium carbide dissolution. The isotachophoretic sample stacking was used to compensate for the perchlorate matrix interference. Simple electrolyte composed of 120 mM formiate buffer, pH 3.8 enabled the nitrate and nitrite determination in the presence of up to 1000-fold excess of perchlorate with 2 μM and 4 μM detection limits for nitrate and nitrite, respectively. The proposed method was applied to the determination of nitrate and nitrite in high-salt non-irradiated uranium carbide dissolution samples.     

12.

Extraction Spectrophotometric Determination of Trace Amounts of Perchlorate Based on Ion-Pair Formation with Thionine     

N. Pourreza  H. Z. Mousavi 《Journal of Analytical Chemistry》2005,60(9):816-818

A simple, rapid, and sensitive extraction-spectrophotometric method has been developed for the determination of trace amounts of perchlorate. This method is based on the extraction of perchlorate as an ion pair with thionine into isobuthyl methyl ketone and measuring the absorbance of the organic phase at 603 nm. The effect of different variables such as pH, reagent concentrations, and standing time was investigated and optimum conditions were established. The effects of other cations and anions on the extraction were also studied. The calibration curve was linear in the range of 40–1000 ng mL^?1 with correlation coefficient of 0.9998. The detection limit based on 3S_b criterion was 23 ng mL^?1 and the relative standard deviation for 400 ng mL^?1 of perchlorate was 1.9%. The proposed method was applied to determination of perchlorate in water samples.     

13.

Simultaneous determination of microgram amounts of chlorine or bromine or iodine and sulfur in organic compounds     

A. Mazzeo-Farina  P. Mazzeo 《Microchemical Journal》1978,23(2):137-141

A general method for the simultaneous and rapid determination of microgram amounts of chlorine or bromine or iodine and sulfur in organic compounds is described.The procedure is based on the combustion of the sample, containing approximately 0.005 meq of Cl or Br or I and 0.005 meq of S. by the Schöniger flask technique, using potassium hydroxide and hydrazine hydrate as absorption solution. The excess of hydrazine is eliminated with hydrogen peroxide after combustion.This method allows complete reduction of halogens to halides and oxidation of sulfur to sulfate.The halide ions are titrated with mercuric perchlorate and diphenylcarbazone as indicator; the sulfate ions with barium perchlorate and dimethylsulfonazo(III) as indicator.The results obtained are in good agreement with calculated values.     

14.

A rapid and precise micro-heterometric determination of gold,palladium or platinum with nitron in thiocyanate solutions: A study of the reactions and of the compounds     

M. Bobtelsky  J. Eisenstaedter 《Analytica chimica acta》1959

Methods are presented for a rapid and precise determination of gold (III), pallahdium or platinuin(IV) either alone or in mixtures. The heterometric titrations were carried out in thiocyanate solutions with nitron. ~1 mg gold. ? 0.5 mg palladium or ~1.5 mg platinum (dissolved in 20 ml auqeous solution) were necessary for a determination, which lasted 5–10 minutes. The error was mostly between zero and 1%.The insoluble compounds, which were quantitatively obtained at the end-points of the titrations, had the following compositions: Au₁N₁; (Au₂N₃) : Pd₂N₃ and Pt₄N₃ (N = nitron)At pH 1–7 all these compounds were entirely insensitive to common masking agents, such as citrate, tartrate, ethylenediaminetetraacetate, pyro- and tripolyphosphate.     

15.

Non-aqueous titration of quinine and quinidine sulphates by use of barium perchlorate     

Zakhari N  Ibrahim F  Kovar KA 《Talanta》1989,36(7):780-782

A simple non-aqueous titration method has been devised for determining the sulphates of quinine and quinidine. The sulphate is precipitated by addition of excess of barium perchlorate solution in acetic and the liberated alkaloid is then titrated in 1:2 anhydrous acetic-dioxan mixture, with an acetic acid solution of perchloric acid. The end-point is determined either visually with Crystal Violet as indicator or potentiometrically with a glass-Ag/AgCl combination electrode. The method is accurate, precise and suitable for routine analysis of pure materials and tablets.     

16.

Self-Assembled Monolayers of Nitron: Self-Activated and Chemically Addressable N-Heterocyclic Carbene Monolayers with Triazolone Structural Motif     

Einav Amit  Iris Berg  Dr. Elad Gross 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(57):13046-13052

N-heterocyclic carbenes (NHCs) have emerged as a unique molecular platform for the formation of self-assembled monolayers (SAMs) on various surfaces. However, active carbene formation requires deprotonation of imidazolium salt precursors, which is mostly facilitated by exposure of the salt to exogenous base. Base residues were found to be adsorbed on the metal surface and hindered the formation of well-ordered carbene-based monolayers. Herein, we show that nitron, a triazolone-based compound that freely tautomerizes to a carbene, can spontaneously self-assemble into monolayers on Pt and Au surfaces, which obviates the necessity for base-induced deprotonation for active carbene formation. SAMs of nitron were found to be thermally stable and could not be displaced by thiols, and thus their high chemical stability was demonstrated. The amino group in surface-anchored nitron was shown to be chemically available for S_N2 reactions, and makes surface-anchored nitron a chemically addressable cross-linking reagent for surface modifications.     

17.

Photometrische Bestimmung von Perchlorat mit Ferroin     

Zbigniew Gregorowicz  Franciszek Buhl  Zdzislaw Klima 《Mikrochimica acta》1963,51(1):116-121

Zusammenfassung Ein Verfahren zur photometrischen Bestimmung des Perchlorations wurde ausgearbeitet. Die Untersuchungslösung wird mit überschüssigem Ferroin und mit Chloroform versetzt. Der Niederschlag wird, abfiltriert und der Ferroinüberschuß im Filtrat photometrisch bestimmt. Für die Bestimmung kleiner Perchloratmengen zwischen 0,2 und 1 mg extrahiert man den gefärbten Ferroinperchloratkomplex mit n-Amylalkohol und photometriert die alkoholische Phase. Der Einfluß von Fremdionen auf die Analysenergebnisse wurde untersucht.

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Summary A method was worked out for the photometric determination of perchlorate ion. The test solution is treated with excess ferroin and chloroform. The precipitate is filtered off and the excess ferroin in the filtrate is determined photometrically. When slight amounts of perchlorate are to be determined, say between 0.2 and 1 mg, the colored ferroin-perchlorate complex is extracted withn-amyl alcohol and the alcoholic phase is photometerized. The effect of foreign ions on the analytical findings was studied.

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Résumé On a mis au point un procédé pour le dosage photométrique de l'ion perchlorate. On additionne la solution à l'étude de ferroine et de chloroforme. en excès. Le précipité est séparé par filtration et l'excès de ferroine dosé photométriquement sur le filtrat. Pour le dosage de petites quantités de perchlorate, entre 0,2 et 1 mg, on extrait le complexe coloré perchlorate de ferroine par l'alcooln-amylique et l'on effectue la photométrie sur la phase alcoolique. On a étudié l'influence des ions étrangers sur les résultats d'analyse.

     

18.

高效液相色谱串联质谱法测定牛奶中的高氯酸盐   总被引：3，自引：0，他引：3  

刘艳英  吴敏  林立毅  周昱 《分析测试学报》2011,30(7):821-824

建立了高效液相色谱-串联质谱测定牛奶中高氯酸盐的方法.样品经1%乙酸-乙腈(体积比1:4)混合溶液提取,于6 000 r/min离心20 min后,经0.2μ m的尼龙滤膜、On-GuardⅡRP柱、On-GuardⅡAg柱和On-GuardⅡBa柱净化,最大反相性能色谱柱C12(Synergi 4u MAX-RP 8...     

19.

Thallic perchlorate in acid medium as a reagent for oxidimetric determination of ascorbic acid in drugs and fruit     

Gupta D  Sharma PD  Gupta YK 《Talanta》1975,22(10-11):913-914

Thallic perchlorate is used for determination of ascorbic acid either by direct titration in acid medium (0.5N) or indirectly by addition of excess of the reagent and iodometric determination of the excess. The method is applicable to fruit juices and vitamin C tablets.     

20.

Coulometric titration of bases in acetic acid and acetonitrile media     

Vajgand VJ  Mihajlović R 《Talanta》1969,16(9):1311-1317

The working conditions and the results for coulometric titration of milligram amounts of some bases in 0.1M sodium perchlorate in a mixture of acetic acid and acetic anhydride (1:6), are given. Determinations were made both by coulometric back-titration or direct titration at the platinum anode. Back-titration was done in the catholyte, by coulometric titration of the excess of added perchloric acid. The titration end-point was detected photometrically with Crystal Violet as indicator. The direct titration of bases was done at the platinum anode, in the same electrolyte, to which hydroquinone was added as anode depolarizer and as the source of hydrogen ions, Malachite Green being used as indicator. Similarly, bases can be determined in acetonitrile if sodium perchlorate, hydroquinone and Malachite Green are added to the solvent. Errors are below 1 %, and the precision is satisfactory.     

Perchlorate			Nitrate
Taken (μg)	Found (μg)	Error (%)	Taken (μg)	Found (μg)	Error (%)
400	404	+ 1.00	248	250	+0.81
400	400	0.00	496	492	?0.81
400	400	0.00	992	992	0.00
800	796	?0.50	248	248	0.00
600	602	+0.33	248	245	?1.21
800	792	?1.25	496	498	+0.40

Infrared spectra for the identification of some inorganic anions using nitron as precipitant

Summary Using infrared absorption spectroscopy a method has been developed which permits the identification, either singly or in admixture, of the following anions: ferrocyanide, ferricyanide, cobalticyanide, chlorate, bromate, perchlorate, periodate, nitrate, nitrite, tungstate, molybdate and chromate. The anions are precipitated by nitron, and using the KBr-disc technique characteristic bands are obtained in the near infrared.

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Zusammenfassung Durch Infrarotabsorptionsspektroskopie lassen sich entweder allein oder in Gemischen folgende Anionen identifizieren: Cyanoferrat(II), Cyanoferrat(III), Cyanokobaltat, Chlorat, Bromat, Perchlorat, Perjodat, Nitrat, Nitrit, Wolframat, Molybdat und Chromat. Die Anionen werden mit Nitron gefällt und geben bei Verwendung einer Kaliumbromid-Linse charakteristische Banden im nahen Infrarot.

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Résumé On a développé une méthode permettant l'identification par spectrographie d'absorption infrarouge des anions suivants, séparément ou en mélanges: ferrocyanure, ferricyanure, cobalticyanure, chlorate, bromate, perchlorate, periodate, nitrate, nitrite, tungstate, molybdate et chromate. On précipite les anions par le nitron et l'on met en évidence les bandes caractéristiques dans l'infrarouge proche, par la technique à la pastille de KBr.

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Dedicated to ProfessorA. A. Benedetti-Pichler on the occasion of his 70th birthday.

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One of us (S. A. E. S.) acknowledges gratefully the award of a scholarship from the U. A. R. Government, which has enabled him to take part in this work.     

Nitron as a titrant in potentiometric determination of nitrate

A volumetric method of nitrate determination has been developed, using nitron as a titrant and detecting the end-point potentiometrically with a membrane electrode sensitive to nitrate. To get a better insight into the characteristics of the system, the acid dissociation constant of nitron was evaluated spectrophotometrically (pK(a) = 10.34). The solubility product of nitron nitrate was found to be 1.78 +/- 0.03 x 10(-6) (20 degrees , 0.05M K(2)SO(4)). The optimal nitrate concentration for titration is about 0.01M and this method may be successfully applied for determination of nitrate nitrogen in fertilizer samples.     

Association studies of tetramethylguanidinium perchlorate and tetramethylguanidinium chloride in ethanol solutions at 25°C

Practical osmotic coefficients of ethanol solutions of tetramethylguanidinium perchlorate and tetramethylguanidinium chloride were determined by the isopiestic method at 25°C. The relations for the concentration dependences of practical osmotic coefficients, mean molal activity coefficients of solutes and for the excess Gibbs free energies of solutions and partial molal excess Gibbs free energies of solutes and solvents are given in analytical form. The results obtained are compared with those reported previously; in the case of tetramethylguanidinium perchlorate with its aqueous and methanol solutions, in the case of tetramethylguanidinium chloride with its aqueous solutions. The non-ideal behavior of the systems investigated is discussed on the basis of the structure of solute species, as well as on the nature of the solvent.     

Capillary electrophoresis determination of nitrate and nitrite in high-salt perchlorate solutions for the UC dissolution study

The capillary electrophoresis method with direct UV detection is proposed for the determination of nitrite and nitrate in high-salt perchlorate solutions issued from uranium carbide dissolution. The isotachophoretic sample stacking was used to compensate for the perchlorate matrix interference. Simple electrolyte composed of 120 mM formiate buffer, pH 3.8 enabled the nitrate and nitrite determination in the presence of up to 1000-fold excess of perchlorate with 2 μM and 4 μM detection limits for nitrate and nitrite, respectively. The proposed method was applied to the determination of nitrate and nitrite in high-salt non-irradiated uranium carbide dissolution samples.     

Extraction Spectrophotometric Determination of Trace Amounts of Perchlorate Based on Ion-Pair Formation with Thionine

A simple, rapid, and sensitive extraction-spectrophotometric method has been developed for the determination of trace amounts of perchlorate. This method is based on the extraction of perchlorate as an ion pair with thionine into isobuthyl methyl ketone and measuring the absorbance of the organic phase at 603 nm. The effect of different variables such as pH, reagent concentrations, and standing time was investigated and optimum conditions were established. The effects of other cations and anions on the extraction were also studied. The calibration curve was linear in the range of 40–1000 ng mL^?1 with correlation coefficient of 0.9998. The detection limit based on 3S_b criterion was 23 ng mL^?1 and the relative standard deviation for 400 ng mL^?1 of perchlorate was 1.9%. The proposed method was applied to determination of perchlorate in water samples.     

Simultaneous determination of microgram amounts of chlorine or bromine or iodine and sulfur in organic compounds

A general method for the simultaneous and rapid determination of microgram amounts of chlorine or bromine or iodine and sulfur in organic compounds is described.The procedure is based on the combustion of the sample, containing approximately 0.005 meq of Cl or Br or I and 0.005 meq of S. by the Schöniger flask technique, using potassium hydroxide and hydrazine hydrate as absorption solution. The excess of hydrazine is eliminated with hydrogen peroxide after combustion.This method allows complete reduction of halogens to halides and oxidation of sulfur to sulfate.The halide ions are titrated with mercuric perchlorate and diphenylcarbazone as indicator; the sulfate ions with barium perchlorate and dimethylsulfonazo(III) as indicator.The results obtained are in good agreement with calculated values.     

A rapid and precise micro-heterometric determination of gold,palladium or platinum with nitron in thiocyanate solutions: A study of the reactions and of the compounds

Methods are presented for a rapid and precise determination of gold (III), pallahdium or platinuin(IV) either alone or in mixtures. The heterometric titrations were carried out in thiocyanate solutions with nitron. ~1 mg gold. ? 0.5 mg palladium or ~1.5 mg platinum (dissolved in 20 ml auqeous solution) were necessary for a determination, which lasted 5–10 minutes. The error was mostly between zero and 1%.The insoluble compounds, which were quantitatively obtained at the end-points of the titrations, had the following compositions: Au₁N₁; (Au₂N₃) : Pd₂N₃ and Pt₄N₃ (N = nitron)At pH 1–7 all these compounds were entirely insensitive to common masking agents, such as citrate, tartrate, ethylenediaminetetraacetate, pyro- and tripolyphosphate.     

Non-aqueous titration of quinine and quinidine sulphates by use of barium perchlorate

A simple non-aqueous titration method has been devised for determining the sulphates of quinine and quinidine. The sulphate is precipitated by addition of excess of barium perchlorate solution in acetic and the liberated alkaloid is then titrated in 1:2 anhydrous acetic-dioxan mixture, with an acetic acid solution of perchloric acid. The end-point is determined either visually with Crystal Violet as indicator or potentiometrically with a glass-Ag/AgCl combination electrode. The method is accurate, precise and suitable for routine analysis of pure materials and tablets.     

Self-Assembled Monolayers of Nitron: Self-Activated and Chemically Addressable N-Heterocyclic Carbene Monolayers with Triazolone Structural Motif

N-heterocyclic carbenes (NHCs) have emerged as a unique molecular platform for the formation of self-assembled monolayers (SAMs) on various surfaces. However, active carbene formation requires deprotonation of imidazolium salt precursors, which is mostly facilitated by exposure of the salt to exogenous base. Base residues were found to be adsorbed on the metal surface and hindered the formation of well-ordered carbene-based monolayers. Herein, we show that nitron, a triazolone-based compound that freely tautomerizes to a carbene, can spontaneously self-assemble into monolayers on Pt and Au surfaces, which obviates the necessity for base-induced deprotonation for active carbene formation. SAMs of nitron were found to be thermally stable and could not be displaced by thiols, and thus their high chemical stability was demonstrated. The amino group in surface-anchored nitron was shown to be chemically available for S_N2 reactions, and makes surface-anchored nitron a chemically addressable cross-linking reagent for surface modifications.     

Photometrische Bestimmung von Perchlorat mit Ferroin

Zusammenfassung Ein Verfahren zur photometrischen Bestimmung des Perchlorations wurde ausgearbeitet. Die Untersuchungslösung wird mit überschüssigem Ferroin und mit Chloroform versetzt. Der Niederschlag wird, abfiltriert und der Ferroinüberschuß im Filtrat photometrisch bestimmt. Für die Bestimmung kleiner Perchloratmengen zwischen 0,2 und 1 mg extrahiert man den gefärbten Ferroinperchloratkomplex mit n-Amylalkohol und photometriert die alkoholische Phase. Der Einfluß von Fremdionen auf die Analysenergebnisse wurde untersucht.

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Summary A method was worked out for the photometric determination of perchlorate ion. The test solution is treated with excess ferroin and chloroform. The precipitate is filtered off and the excess ferroin in the filtrate is determined photometrically. When slight amounts of perchlorate are to be determined, say between 0.2 and 1 mg, the colored ferroin-perchlorate complex is extracted withn-amyl alcohol and the alcoholic phase is photometerized. The effect of foreign ions on the analytical findings was studied.

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Résumé On a mis au point un procédé pour le dosage photométrique de l'ion perchlorate. On additionne la solution à l'étude de ferroine et de chloroforme. en excès. Le précipité est séparé par filtration et l'excès de ferroine dosé photométriquement sur le filtrat. Pour le dosage de petites quantités de perchlorate, entre 0,2 et 1 mg, on extrait le complexe coloré perchlorate de ferroine par l'alcooln-amylique et l'on effectue la photométrie sur la phase alcoolique. On a étudié l'influence des ions étrangers sur les résultats d'analyse.

     

高效液相色谱串联质谱法测定牛奶中的高氯酸盐

建立了高效液相色谱-串联质谱测定牛奶中高氯酸盐的方法.样品经1%乙酸-乙腈(体积比1:4)混合溶液提取,于6 000 r/min离心20 min后,经0.2μ m的尼龙滤膜、On-GuardⅡRP柱、On-GuardⅡAg柱和On-GuardⅡBa柱净化,最大反相性能色谱柱C12(Synergi 4u MAX-RP 8...     

Thallic perchlorate in acid medium as a reagent for oxidimetric determination of ascorbic acid in drugs and fruit

Thallic perchlorate is used for determination of ascorbic acid either by direct titration in acid medium (0.5N) or indirectly by addition of excess of the reagent and iodometric determination of the excess. The method is applicable to fruit juices and vitamin C tablets.     

Coulometric titration of bases in acetic acid and acetonitrile media

The working conditions and the results for coulometric titration of milligram amounts of some bases in 0.1M sodium perchlorate in a mixture of acetic acid and acetic anhydride (1:6), are given. Determinations were made both by coulometric back-titration or direct titration at the platinum anode. Back-titration was done in the catholyte, by coulometric titration of the excess of added perchloric acid. The titration end-point was detected photometrically with Crystal Violet as indicator. The direct titration of bases was done at the platinum anode, in the same electrolyte, to which hydroquinone was added as anode depolarizer and as the source of hydrogen ions, Malachite Green being used as indicator. Similarly, bases can be determined in acetonitrile if sodium perchlorate, hydroquinone and Malachite Green are added to the solvent. Errors are below 1 %, and the precision is satisfactory.