Spectrophotometric method for the determination of demeclocycline using sodium molybdate as analytical reagent

By means of spectroscopic methods it has been found that demeclocycline reacts with molybdate ions forming a complex compound [MoO₃HDMTC]^2–. The relative stability constant of this compound has been determined by applying spectrophotometric methods. Under optimum conditions for complex formation a very sensitive spectrophotometric method for the estimation of demeclocycline in the concentration range 5.0–35.1 g/ml is proposed. The detection limit of the method is 2.5 g/ml of demeclocycline. The relative standard deviation (n=10) varies between 0.76% and 1.46%. The method proved to be accurate and sensitive for the analysis of the demeclocycline content in tablets.     

5:6-Benzoquinaldinic acid as an analytical reagent: Determination of titanium

The reagent 5 :6 -benzoquinaldisic acid precipitates titanium(lV) completely from solution at and above pH 3.0 in the presence of rare earths. Coprecipitation of magnesium and the alkaline earths is easily prevented by the addition of ammonium chloride. Separation from iron(III), thorium or zirconium can be carried out in the presence of complexone III. magnesium sulphate being used as a demasking agent. Separation from aluminium is not possible. The titanium precipitate is not of definite composition and so it is ignited to the oxide before weighing.     

Chloramine-T (N-chloro-p-toluenesulfonamide sodium salt), a versatile reagent in organic synthesis and analytical chemistry: An up to date review

Chloramine-T (CAT), the sodium salt of N-chloro-p-toluenesulfonamide, is a low-cost mild oxidizing agent with a wide range of uses. Most importantly, it can be used in acidic, neutral, and basic conditions. As a result, it’s been widely used in chemistry, particularly in organic synthesis and analytical chemistry. Chloramine-T acts as a source of halonium cation and nitrogen anion and thus acts as base and nucleophile. It reacts with a wide range of functional groups and carries different molecular transformations. This paper thoroughly summarises and highlights the synthetic and analytical effectiveness of CAT. This study focuses on current developments as well as some older techniques in which CAT has been employed as an oxidizing agent. This review article stretches a comprehensive profile of the CAT reagent in organic synthesis and analytical chemistry, which will be very useful for further research exploration in this field.     

O-carboxyphenyl azo chromotropic acid (sodium salt) as an analytical reagent

Summary 0-carboxyphenyl azo chromotropic acid (sodium salt), named as chromotrope 2 C, is used as a new colorimetric reagent for the determination of micro amounts of thorium and aluminium. The blue-violet and red-violet complexes show maximum absorption at 590 nm and the colour systems obey Beer's law from 0.1 to 8 ppm for thorium and 0.1 to 1ppm for aluminium. However, their optimum concentration ranges are from 1.6 to 8 ppm for thorium and 0.2 to 0.8 ppm for aluminium, where the percent relative errors per 1% absolute photometric error are, respectively, 3.06 and 2.94. The composition of the complexes, as elucidated by the continuous variation method, suggests a metal to reagent ratio of 23 for thorium and a ratio of 11 for aluminium. The instability constants for the complexes are of the order of 4.044×10^–10 and 1.006 × 10^–6 at 30°C.Part I, see Z. analyt. Chem. 174, 197 (1960)     

O-carboxyphenyl azo chromotropic acid (sodium salt) as an analytical reagent

Summary O-carboxyphenyl azo chromotropic acid (sodium salt), chromotrope 2C, is introduced as a new metallochromic indicator. Its colour reactions with a few metal ions have been utilised for their quantitative chelatometric determinations with EDTA.     

Trityl tetraphenylborate as a reagent in organometallic chemistry

Trityl tetraphenylborate, prepared from trityl triflate and sodium tetraphenylborate, is shown to be a useful hydride and methyl anion abstraction reagent for organometallic compounds. It reacts with (η⁵-C₅Me₅)(PMe₃)₂RuMe to give the fulvene complex [η⁴-C₅Me₄CH₂)(PMe₃)₂RuMe]BPh₄, and with (η⁵-C₅H₅)₂ZrMe₂ in acetonitrile-d₃ to afford the cationic methyl derivative [(η⁵-C₅H₅)₂ZrMe(NCCD₃)]BPh₄.     

Solochrome Green V as a new analytical reagent

Summary The acid-base properties of Solochrome Green V have been studied with the object of testing its use as a metal indicator or colorimetric reagent. The pK values of the three steps of ionisation of the free acid were evaluated. The dye has proved to be a suitable indicator in EDTA titrations of zinc and manganese as well as a colorimetric reagent for the microdetermination of zinc. The method is highly sensitive that by its application 0.05 ppm Zn can be determined with fair accuracy.     

Chemistry as a branch of analytical chemistry

Summary An approach to the teaching of chemistry and of analytical chemistry is presented, suitable for use at the 2nd or 3rd year level. The present tendency to subdivide chemistry into many small units is countered by this suggestion to use a comprehensive course on analytical chemistry as a means of reuniting the subdivisions of modern chemistry.

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Chemie als Zweig der analytischen Chemie

Zusammenfassung Der Unterricht in Chemie und analytischer Chemie des 2. oder 3. Studienjahres wird von einem neuen Gesichtspunkt aus gesehen: der heutigen Tendenz, Chemie in diverse Teilgebiete zu zergliedern, wird der Vorschlag eines allgemeinen Lehrganges in analytischer Chemie entgegengestellt, mit dessen Hilfe eine Wiedervereinigung der Teilgebiete der modernen Chemie erzielt werden kann.

Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9. 1972 in Heidelberg, Germany.     

5: 6-Benzoquinaldinic acid as an analytical reagent: Determination of thorium and zirconium

Thorium and zirconium are determined in the presence of rare earths, alkaline earths and magnesium, when precipitated from weakly acid solution with 5:6-benzoquinaldinic acid. Thorium is completely precipitated at pH 3.0 as Th(C₁₄H₈O₂N)₄, but though zirconium is precipitated at the lower pH of 1.8, its composition is not stoichiometric and hence is ignited to the oxide before weighing. Co-precipitation of magnesium and alkaline earths is prevented by the addition of ammonium chloride.     

2'-hydroxychalcone as an analytical reagent for beryllium

Several o-hydroxychalcones were examined to develop specific reagents for the precipitation of beryllium in the presence of elements such as aluminium and iron, which occur in its ores. All these reagents showed specificity only in the presence of EDTA. Among them, the readily obtainable 2'-hydroxychalcone is proposed as a new specific reagent for beryllium. The chalcone complex can be dried to constant weight at 105-110 degrees and the conversion factor is 0.01978. A probable structure for the complex has been suggested. Quantitative separation of beryllium from aluminium and iron carried out by this method gave good results. This method was applied for the gravimetric determination of beryllium in beryl and the results were in good agreement with those obtained by the oxide and pyrophosphate methods.     

Studies on the analytical chemistry of iodonium compounds

Summary A procedure is described for the determination of the diphenyliodonium cation by weighing as the molybdophosphate. The range of the method is 10–200 mg of cation. The effects of interfering substances and the conditions of precipitation are discussed and a coefficient of variation of 0.11% has been obtained.

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Zusammenfassung Ein Verfahren zur gravimetrischen Bestimmung von Diphenyljodonium-Kation als Molybdänphosphat wurde beschrieben. Es ermöglicht die Bestimmung von 10 bis 200 mg Kation. Die Wirkung störender Substanzen und die Fällungsbedingungen wurden erörtert. Ein Variationskoeffizient von 0,11% wurde festgestellt.

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Résumé On décrit un procédé de dosage du cation diphényliodonium par pesée à l'état de phosphomolybdate. La méthode couvre le domaine de 10–200 mg de cation. On discute les effets des substances qui interfèrent et les conditions de précipitation et l'on obtient un coefficient de variation de0,11%.

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Part III: Mikrochim. Acta [Wien] 1966, 1051.     

Dimethyl carbonate as a novel methylating reagent for fatty acids in analytical pyrolysis

Dimethyl carbonate (DMC) was investigated as a mild, harmless and odorless reagent for pyrolytic methylation of fatty acids. Soybean oil was selected as test material for its high content of (poly)unsaturated fatty acids. Pyrolyses were performed at 500, 700 and 900 degrees C by means of a heated platinum filament pyrolyser on-line and off-line to the GC-MS apparatus. Methyl esters of palmitic, linoleic, oleic and stearic acid were formed as prominent products from off-line pyrolysis of soybean oil in the presence of DMC and zeolite 13X. Fatty acid methyl esters (FAMEs) were not observed at important levels in the absence of zeolite, while on-line Py-GC-MS experiments resulted principally in the formation of free fatty acids and hydrocarbons. The FAME profiles obtained from the DMC/zeolite off-line pyrolysis were compared to those resulting from tetramethylammonium hydroxide (TMAH) thermochemolysis and BF3-methanol procedure. The observed differences between pyrolysis and methanolysis methods were principally attributed to the thermal degradation of unsaturated fatty acids. The effectiveness of the DMC/zeolite pyrolytic methylation was further demonstrated by the analysis of tripalmitine and soybean seeds.     

Resorcinol as an analytical reagent for the spectrophotometric determination of uranium

A spectrophotometric study of the reaction of uranyl acetate and resorcinol shows that an orange-red coloured resorcinolate of composition 1:2 is formed. This colour reaction can be conveniently used for the spectrophotometric estimation of uranium at PH 4.72.     

Benzeneacetaldehyde-4-hydroxy-alpha-oxo-aldoxime as a new analytical reagent for the spectrophotometric determination of cobalt

Benzeneacetaldehyde-4-hydroxy-α-oxo-aldoxime is proposed as a new sensitive and selective reagent for the spectrophotometric determination of cobalt. The reagent reacts with cobalt in the pH range 8.6–9.4 to form a yellow colored 1:3 chelate which is very well extracted in chloroform. Beer's law is obeyed in the concentration range 0.05–1.3 μg ml⁻¹ cobalt. The molar absorptivity of the extracted species is 2.746×10⁴ l mol⁻¹ cm⁻¹ at 390 nm. The proposed method is highly sensitive, selective, simple, rapid, accurate and has been satisfactorily applied for the determination of cobalt in synthetic mixtures, pharmaceutical samples, biological samples and alloys.     

Isotopes as tracers in analytical chemistry

A survey is given of the availability of radioactive and of concentrated heavy isotopes in Holland and of the instruments for their measurements.The principles of the application of tracers in analytical chemistry are reviewed and examples of the different kinds are described. Finally the determination of elements by induced radioactivity and by neutron absorption is dealt with.     

A study of potassium dicyanoguanidine as a possible analytical reagent

Summary The following ions: Cu⁺⁺, Ag⁺, Hg₂ ⁺⁺, Hg⁺⁺, PtCl₆ ^–-, Pd⁺⁺, Au⁺⁺⁺ in acid solution, produced insoluble compounds with an aqueous solution of potassium dicyanoguanidine. Ferric ion produced a red coloration with the same reagent. The results obtained with PtCl₆ ^–-, Pd⁺⁺ and Fe⁺⁺⁺ are sufficiently characteristic to be used for the detection of these ions.

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Zusammenfassung Folgende Ionen geben in saurem Milieu mit einer wässerigen Lösung von Kalium-dicyanoguanidin unlösliche Verbindungen: Cu⁺⁺, Ag⁺, Hg₂ ⁺⁺, Hg⁺⁺, PtCl₆ ^–-, Pd⁺⁺ und Au⁺⁺⁺. Ferriionen geben mit demselben Reagens Rotfärbung. Die mit PtCl₆ ^–-, Pd⁺⁺ und Fe⁺⁺⁺ erhaltenen Reaktionsprodukte sind ausreichend charakteristisch, um für den Nachweis dieser Ionen verwendet werden zu können.

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Résumé Les ions suivants: Cu⁺⁺, Ag⁺, Hg₂ ⁺⁺, Hg⁺⁺, PtCl₆ ^–-, Pd⁺⁺, Au⁺⁺⁺, en solution acide, ont donné des composés insolubles avec une solution aqueuse du dérivé potassé de la dicyanoguanidine. L'ion ferrique a donné une coloration rouge avec le même réactif. Les résultats obtenus avec PtCl₆ ^–-, Pd⁺⁺ et Fe⁺⁺⁺ sont suffisamment caractéristiques pour être employés dans la recherche de ces ions.

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With 2 figures.     

Studies on the existence of a tautomeric equilibrium in solutions of the analytical reagent dithizone

The traditional view that solutions of dithizone in organic solvents comprise equilibrium mixtures of thiol and thione forms which are individually responsible for the characteristic strong visible absorption bands around 440 and 620 nm is examined critically. Fourier transform ₁H and ₁₃C NMR spectroscopic measurements on dithizone, seven of its alkyl-substituted homologues, and on its ₁₃C- and ₁₅N-labelled analogues point to the existence of only a single molecular species in chloroform, benzene or acetone. The marked solvatochromism, however, has yet to be explained. Modifications to established synthetic routes are reported which are especially suitable for the small-scale preparation of isotopically-labelled dithizone analogues.     

荧光试剂SPAEC的合成及分析化学特性研究

合成了新荧光试剂2-(5'-磺基-2'-苯酚-1'-偶氮)-5-乙氨基-4-甲酚(SPAEC)。用等色点光度法测得试剂的离解常数为pK1=3.42, pK2=5.46, pK3=7.99。考察了SPAEC与金属离子的螯合显色和荧光反应; 建立了测定镓、铝的反应条件, 在PH3.8-5.4或PH4.0-5.5的乙酸缓冲介质中均形成:1型具荧光活性的有色螯合物, 可相应测定15-150ppb镓及1.5-30ppb铝, 试用于半导体及合金分析。研究了Kalman滤波荧光光度法, 实现了镓与铝的同时测定, 所适应的浓度比例范围为40:1(0)-1(0):14。     

Acenaphthenequinonedioxime as an analytical reagent: Determination of nickel in mixtures

Summary The titled reagent (ANDO) has been used as a reagent for gravimetric determination of nickel and for its separation from common cations and anions. Nickel (II) precipitates quantitatively by ANDO within the pH range 6.8–8.4. After drying the precipitate at 110°, its composition corresponds to the formula Ni(C₁₂H₇O₂N₂)₂. Many commonly associated ions, except Fe(III), Co(II) and Cu(II), do not interfere. Solvent-extraction techniques have been utilized to separate Cu(II) and Co (II) from the binary mixture. For masking Fe(III) excess citrate ion has been used. Elemental analysis confirms 12 metal-ligand ratio. The complex is approximately diamagnetic ( _eff=0.95 B. M.) and gives typical d-d spectral bands as generally observed in square planar complexes involving d⁸ electronic configuration. Electronic spectra of the metal chelate in pyridine are discussed and results of thermo gravimetric analysis are also presented. I. R. and far I. R. spectral analysis indicate the involvement of strong hydrogen bridges and metal-nitrogen bond.

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Acenaphthenchinondioxim als analytisches Reagens: Bestimmung von Nickel in Gemischen

Zusammenfassung Acenaphthenchinondioxim (ANDO) wurde für die gravimetrische Bestimmung von Nickel und für dessen Trennung von üblichen Kationen und Anionen verwendet. Ni(II) wird mit diesem Reagens quantitativ ausgefällt innerhalb des pH-Bereiches 6,8–8,4. Getrocknet bei 110° entspricht der Niederschlag der Zusammensetzung Ni(C₁₃H₇O₂N₂)₂. Viele üblicherweise anwesende Ionen, ausgenommen Fe(III), Co(II) und Cu(II), stören nicht. Die beiden letztgenannten lassen sich durch Extraktionen abtrennen, Fe(III) wird mit Citrat maskiert. Das Metall-Ligand-Verhältnis beträgt 12. Die Komplexverbindung ist nahezu diamagnetisch ( _eff=0,95 B. M.) und gibt typische d-d-Spektralbanden, wie sie üblicherweise von planar-quadratischen Komplexen mit d⁸-Elektronenkonfiguration gezeigt werden. Die Elektronenspektren des Metallchelates in Pyridin wurden diskutiert und die Ergebnisse der thermogravimetrischen Untersuchung angeführt. IR- und ferne IR-Analyse weisen auf die Anwesenheit starker Wasserstoffbrücken und auf eine Metall-Stickstoff-Bindung hin.

     

5:6-Benzoquinaldinic acid as a colorimetric reagent

5:6-Benzoquinaldinic acid, like α-picolinic acid, has been utilised as a colorimetric reagent for iron (ous). Transmittancy measurements with the Lumetron 402 EF having a cell of capacity 16 ml and thickness 20 mm show that iron from 0.4 to 20 p.p.m. may be estimated, while that with Klett-Summerson photoelectric colorimeter, iron from 5 to 50 p.p.m. may be determined in a tube cell of capacity 15 ml and diam. 12 mm. The optimum range with the minimum error is from 2.4 to 14 p.p.m. The effect of diverse ions, reagent, reducing agent, cyanide and other physical conditions as temperature, time, etc. on the colour system has been investigated.