Extraction-photometric determination of thorium with chlorophosphonazo-III

A simple and rapid spectrophotometric determination of thorium is described. The thorium-chlorophosphonazo-III complex is extracted into 3-methyl-1-butanol from 2.0–3.0 M hydrochloric acid solution. Maximum absorbance occurs at 620 and 670 nm and Beer's law is obeyed at the latter wavelength over the range of 0–15 μg per 10 ml of the organic phase. The molar absorptivity is 12.2·10⁴ l mole^-1 cm^-1 at 670 nm. Thorium can be determined in the presence of fluoride, oxalate, sulfate and EDTA. Many common cations do not interfere, but uranium, zirconium and niobium interfere seriously.     

Spectrofluorimetric determination of 1-(3-chlorophenyl)-4-methyl-7,8-dimethoxy-5H-2,3-benzodiazepine

A sensitive fluorimetric method for the determination of 1-(3-chlorophenyl)-4-methyl-7,8-dimethoxy-5H-2,3-benzodiazepine (5 × 10^?8?6 × 10^?4) g ml^?1) is described. The method is based on acid hydrolysis and aldol condensation in alkaline solution to give a compound which shows intense fluorescence at 440 nm.     

Darstellung und spektroskopische Charakterisierung der reinen Bindungsisomeren [OsCl5(NCS)]2− und [OsCl5(SCN)]2−

Preparation and Spectroscopic Characterization of the Pure Bondisomers [OsCl₅(NCS)]^2? and [OsCl₅(SCN)]^2? The oxidation of [OsCl₅I]^2? with (SCN)₂ in CH₂Cl₂ yields the bondisomers [OsCl₅(NCS)]^2? and [OsCl₅(SCN)]^2?, which are isolated as pure compounds by ion exchange chromatography on DEAE-Cellulose. Only the salts of the N-isomer show significant shifts in the vibrational and electronic spectra caused by polarization of the terminal S depending on the size of the cations and the polarity of the solvents. In the IR and Raman spectra ν_CN(S), ν_CS(N) and δ_NCS are found at higher wave numbers than ν_CN(N), ν_CS(S) and δ_SCN. In the optical spectrum of the red [OsCl₅(SCN)]^2? the charge-transfer S→Os is nearly constant at 538 nm, but the N→Os transition of the yellow to violet coloured N-isomer shifts from 480 nm in organic solvents or in presence of large alkylammonium cations to 516 nm in aqueous solution and to 544 nm in the solid Cs-salt. The optical electronegativities are calculated to χ_opt(–SCN) = 2.6 and χ_opt(–NCS) = 2.6–2.8. According to spinorbit coupling and to lowered symmetry (C_4v) the splitted intraconfigurational transitions are observed at 10 K as weak peaks in the regions 600, 1000 and 2000 nm. The O? O transitions are calculated from the vibrational fine structure. The lowest level of both isomers is confirmed by peaks in the electronic raman spectra. With the parameters ζ(Os^IV) = 3200 cm^?1 and B(? SCN) = 316 cm^?1 or B(? NCS) = 288 cm^?1 there is a good fit of calculated and experimental data, resulting in the nephelauxetic series: F^? > CI^? > SCN^? > Br^? > NCS^? > I^?.     

Extraction-photometric determination of uranium(IV) with chlorophosphonazo-III

A sensitive spectrophotometric method has been developed for the determination of uranium. The uranium(IV)-chlorophosphonazo-III complex is extracted into 3-methyl-1-butanol from 1.5–3.0 M hydrochloric acid solution. Maximal absorbance occurs at 673 nm and Beer's law is obeyed over the range of 0–15 μg per 10 ml of the organic phase. The molar absorptivity is 12.1·10⁴ 1 mole^?1 cm^?1. Uranium can be determined in the presence of fluoride. sulfate and phosphate. Nitrate ion and elements (chromium, copper, iron) which affect the reduction of uranium(VI) or stability of uranium(IV) interfere.     

Flow-injection spectrophotometric determination of palladium in catalysts and dental alloys with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropyl-amino)aniline

2-(5-Bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)aniline rapidly forms a water-soluble complex with palladium in an acetate-buffered medium at pH 3.2.The molar absorptivity of the complex is 9.84×10⁴l mol^?1 at 612 nm. The calibration graph is linear over the range of 10–100 μg l^?1 palladium; the detection limit is 2 μg l^?1 and the relative standard deviation is 0.6% for 100 μg l^?1 palladium. The sample throughput is 50 h^?1. Divalent transition metals (Fe, Ni, Co) do not interfere at levels from 2 to 10 mg l^?1. Interference from copper is prevented by adding 10^?3 M EDTA solution to the carrier stream. Palladium in solutions of catalysts and dental alloys can be determined selectively, sensitively and rapidly.     

Spectrophotometric determination of cadmium with 1-[(5-chloro-2-pyridyl)azo]-2-naphthol

Summary Cadmium(II) reacts with l-[(5-chloro-2-pyridyl)azo]-2-naphthol (5-C1--PAN) in aqueous solution; the complex can be extracted with chloroform at pH 9–11 to give a red solution with an absorption peak at 566 nm. The colour in chloroform is stable and the system conforms to Beer's law; optimal range in the chloroform layer for measurement at 1.00-cm cells is 0.1–1 ppm cadmium. Common cations and anions do not interfere. Large amounts of some cations can be masked by potassium cyanide, the cadmium cyanide complex being demasked by formaldehyde. The proposed method is one of the most sensitive procedure for the determination of cadmium. The molar absorptivity in the chloroform extract is 6.6· 10⁴ 1 mole^–1 cm^–2 at 566 nm.

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Zusammenfassung Cadmium reagiert mit 1-(5-Chlor-2-pyridyl) azo-2-naphthol, 5-C1--PAN, in wäßriger Lösung; der rote Komplex kann bei pH 9–11 mit Chloroform extrahiert werden und hat ein Absorptionsmaximum bei 566 nm. Die chloroformische Lösung ist stabil und entspricht dem Beerschen Gesetz; für die Messung in l-cm-Küvetten eignen sich am besten 0,1–1 ppm Cd. Übliche Ionen stören nicht. Große Mengen einiger Kationen können mit KCN maskiert werden, wahrend [Cd(CN)₄]^2– von Formaldehyd gespalten wird. Die vorgeschlagene Methode ist eine der empfindlichsten für die Bestimmung von Cd. Die molare Extinktion des chloroformischen Extraktes betragt bei 566 nm 6,6 · 10⁴ 1 · mol^–1 · cm^–2.

     

Synthesis and characterization of poly(1,4‐bis((E)‐2‐(3‐dodecylthiophen‐2‐yl)vinyl)benzene) derivatives

New amorphous semiconducting copolymers, poly(9,9‐dialkylfluorene)‐alt‐(3‐dodecylthienyl‐divinylbenzene‐3‐dodecylthienyl) derivatives (PEFTVB and POFTVB), were designed, synthesized, and characterized. The structure of copolymers was confirmed by H NMR, IR, and elemental analysis. The copolymers showed very good solubility in organic solvents and high thermal stability with high T_g of 178–185 °C. The weight average molecular weight was found to be 107,900 with polydispersity of 3.14 for PEFTVB and 76,700 with that of 3.31 for POFTVB. UV–vis absorption studies showed the maximum absorption at 428 nm (in solution) and 435 nm (in film) for PEFTVB and at 430 nm (in solution) and 436 nm (in film) for POFTVB. Photoluminescence studies showed the emission at 498 nm (in solution) and 557 nm (in film) for PEFTVB and at 498 nm (in solution) and 536 nm (in film) for POFTVB. The solution‐processed thin‐film transistors showed the carrier mobility of 2 × 10^?4 cm² V^?1 s^?1 for PEFTVB‐based devices and 2 × 10^?5 cm² V^?1 s^?1 for POFTVB‐based devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3942–3949, 2010     

Temperature dependence of unperturbed dimensions for isotactic poly(2-hydroxyethyl methacrylate)

The unperturbed dimensions of isotactic poly(2-hydroxyethyl methacrylate) (PHEMA) were evaluated from intrinsic viscosity measurements in water, ethanol, 1-propanol, 2-propanol, and 2-butanol under θ conditions over the temperature range of 3.7–32.1°C. The smallest value of unperturbed dimensions (K_θ) and the largest negative temperature dependence of unperturbed dimensions and the polymer–solvent interaction parameter (B) were obtained in aqueous θ solvent relative to the corresponding organic θ solvents. These results were interpreted by the hydrophobic interaction between the hydrophobic groups of isotactic PHEMA and water solvent. The temperature coefficient of the unperturbed dimensions, d ln〈r〉/dT, obtained in this study has a negative value of ?1.44 × 10^?3 deg^?1 under chemically similar θ solvents such as ethanol, 1-propanol, 2-propanol, and 2-butanol where specific solvent effects are eliminated or minimized. In order to obtain the thermodynamic parameters for mixing between isotactic PHEMA and solvents, the plots of the polymer–solvent interaction parameter versus reciprocal absolute temperature (1/T) were carried out. Both the entropy of dilution and enthalpy of dilution show the negative values for water, methanol, and t-butanol, whereas the positive ones for ethanol, 1-propanol, 2-propanol, and 2-butanol. This result indicates that the solution of isotactic PHEMA behave as exothermal systems in the former class of solvents and endothermal ones in the latter class of solvents.     

Extraction-spectrophotometric determination of traces of palladium by reaction between zinc(II) dibenzyldithiocarbamate and palladium(II)/2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

The simple and highly sensitive determination of palladium is based on the reaction between Pd(II)/5-Br-PADAP and Zn(II) DBDTC complexes in 1,2-dichloroethane or toluene at pH 9.7. At 530 nm, the molar absorptivity is about 0.8 × 10⁵ l mol ^?1 cm ^?1. Beer's law is obeyed in the concentration range 0.1–1.2 μg ml ^?1 Pd. Relative standard deviations are 2–5%. Metal ions reacting with either of the organic reagents interfere.     

N-p-tolyl-2-furohydroxamic Acid as the Extracting and Spectrophotometric Reagent for Vanadium(V)

Abstract

A simple and rapid spectrophotometric determination of vanadium(V) is described. The vanadium-N-p-tolyl-2-furohydroxamic acid complex is extracted into chloroform form 6–8 molar hydrochloric acid solution. Maximum absorbance occurs at 540 nm and Beer's Law is obeyed over the range of 0–15 μg of vanadium in the organic phase. The molar absorptivity is 3.0 × 10³ mole^?1 cm^?1 at 540 nm.

Vanadium could be determined in high purity niobium and tantalum metals, cast iron, steel, non ferrous alloys and silicates. Vanadium could be determined in the presence of several commonly occurring cations.     

Spectrophotometric determination of uranium with 1-[(5-Methyl-2-pyridyl)azo]-2-naphthol

Summary Uranium(VI) reacts with 1-[(5-methyl-2-pyridyl)azo]-2-naphthol (5-Me--PAN) in aqueous solution. The complex can be extracted with chloroform at pH 7.0–11.5 to give a red solution with an absorbance peak at 560 nm. The color is stable and the system conforms to Beer's law at the range of 1.5–8 ppm uranium in chloroform layer. Common anions and cations do not interfere. Large amounts of interfering cations can be masked by potassium cyanide, EDTA or triethanolamine. The proposed method is a selective procedure for the determination of uranium. The molar absorptivity in the chloroform extract is 2.1×10⁴ l mole^–1 cm^–1 at 560 nm.

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Zusammenfassung Uran(VI) reagiert mit 1-[(5-Methyl-2-pyridyl)azo]-2-naphthol(5-Me--PAN) in wäßriger Lösung unter Bildung einer mit Chloroform bei pH 7,0–11,5 extrahierbaren, roten Komplexverbindung mit einem Absorptionsmaximum bei 560 nm. Die Färbung ist beständig und folgt dem Beerschen Gesetz zwischen 1,5 und 8 ppm Uran. Die üblichen Ionen stören nicht. Große Mengen störender Kationen können mit Kaliumcyanid, ÄDTA oder Triäthanolamin maskiert werden. Die vorgeschlagene Methode ist für die Uranbestimmung selektiv. Die molare Extinktion des Chloroformextraktes beträgt 2,1×10⁴ l·Mol·^–1 cm^–1 bei 560 nm.

     

Studies in ring-opening polymerization. III. 5-methyl-5-propyl and 5-methyl-5-isopropyl-1,3,2-dioxathiolan-4-one 2-oxide

5-Methyl-5-propyl-1,3,2-dioxathiolan-4-one 2-oxide (MPAS) and 5-methyl-5-isopropyl-1,3,2-dioxathiolan-4-one 2-oxide (MiPAS), which are isomers of the previously studied 5,5-diethyl-1,3,2-dioxathiolan-4-one 2-oxide (DEAS), have been synthesized and their polymerizability compared with that of the last compound. The two unsymmetrically substituted monomers polymerize by a mechanism which is substantially identical to that of their symmetrically substituted counterpart. In dry nonhydroxylic solvents the rate-determining process is the primary scission of the ring, which takes place with elimination of sulfur dioxide and concurrent ring contraction to form an α-lactone intermediate. In this reaction, the parent acid, produced by reaction of the monomer with adventitious traces of moisture, acts as the initiating species. The resultant polymers are all hydroxyl/carboxyl-terminated, but, whereas those derived from the two unsymmetrically substituted monomers are amorphous and readily soluble in a variety of organic solvents, those derived from the diethyl-substituted ring have been shown to be highly crystalline materials which dissolve in very few solvents. The relative polymerization rates are illustrated by the first-order rate constants for decomposition in nitrobenzene at 90°C: DEAS, 20.1 × 10^?5 sec^?1; MiPAS, 11.0 × 10^?5 sec^?1; MPAS, 9.7 × 10^?5 sec^?1. The role of the substituents in determining the magnitude of these constants is discussed in terms of both the Thorpe-Ingold effect and electron donation at C-5.     

Spectrophotometric determination of traces of gallium and indium with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-naphthol (PAN) reacts with either gallium or indium at pH 5–6 giving a red complex in an aqueous medium in the presence of N.N-dimethyl-formamide. The maximum absorption of both PAN complexes of gallium and indium in an aqueous solution is at 545 mμ. The gallium-PAN complex shows a characteristic enhancement of color by addition of small amounts of ethers. Based on this selective enhancement reaction, gallium can be determined in the presence of other metals without separation. The results of determining gallium and indium in the presence of each other are reported. Both gallium and indium form M₂(PAN)₃; but in the presence of certain organic solvents, a different gallium complex, Ga(PAN)₅, and the same indium complex, In₂(PAN)₃, are formed. The reaction of PAN with cadmium can be masked by iodide; an example of determining indium in the presence of cadmium is given. The PAN method has a sensitivity of 0.003 μg/cm² for gallium and 0.005μg/cm² for indium and an absorptivity of 24,900 for the Ga-PAN complex and of 24,500 for the In-PAN complex, respectively. The methods have been successfully applied to the determination of both gallium and indium in germanium thin films.     

Bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulpho propylamino)phenolato]cobaltate(III) as a counter ion for the extraction and spectrophotometric determination of long-chain quaternary ammonium salts and tertiary alkylamines in the presence of each other

The singly charged complex anion bis[2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulphopropylamino)phenolato]cobaltate(III) is intensely purple-violet and is stable over the pH range 1–13. Its absorption spectrum remains the same over this pH range. At pH2, it forms extractable ion pairs with long-chain quaternary ammonium ions and protonated alkylamines. Only the quaternary ammonium ions are extracted into chloroform at pH 11, hence separate extractions allow both types to be determined. The absorbance of the organic phase is measured at 594 nm. The apparent molar absorptivity is 7.0 × 10⁴ l mol^?1 cm^?1. Calibration graphs for zephiramine, benzethonium and hexadecylpyridinium ions are linear over the range 0.1–2 × 10^?6 M. The only interference found was from anionic surfactants. The method is applied to hair and fabric conditioners.     

Spectrophotometric study of the ruthenium(III,II)–2,2′,2″- terpyridine system

Ruthenium(III) reacts with 2,2′,2″-terpyridine in aqueous solution at pH 3.0–4.5, when heated at 85 °C for 2 min, giving a green cationic complex with an absorbance maximum at 690 nm. The color is stable for at least 25 h. The system conforms to Beer's law. The optimal range for measurement (1.00-cm optical path) is 2–10 p.p.m. Ru; the molar absorptivity is 8.3 ·10³. Ruthenium(II) reacts with terpyridine at pH 5.5 to develop an amber cationic complex (absorption maximum at 475 nm) on heating at 95° C for 45 min. The color is apparently stable indefinitely. The system conforms to Beer's law; the optimal range is 1–5 p.p.m. Ru; the molar absorptivity is 1.45·10⁴ l mol^?1 cm^?1. Common anions do not interfere; separation as RuO₄ is necessary when iron and a few other transition cations are present. The green complex, a strong oxidant, is converted to the ruthenium(II) complex by oxidation of water, slowly at room temperature, or more quickly by longer heating and/or higher temperature, and by increase of pH. The Ru(II) complex can be converted to the Ru(III) complex by strong oxidants such as Ce(IV). In the amber complex, the reaction ratio is 1 Ru: 2 terpyridine, in which the ligand is tridentate, whereas in the green complex the reaction ratio is 1 Ru : 3 terpyridine, the latter acting only as a bidentate ligand. Short gentle warming of a mixture of ruthenium(III) and terpyridine first produces a transient unidentified blue-colored species (absorbance at 790 nm).     

Determination trace amounts of thallium after separation and preconcentration onto nanoclay loaded with 1-(2-pyridylazo)-2-naphthol as a new sorbent

A procedure has been proposed for the separation and preconcentration of trace amounts of thallium. It is based on the adsorption of thallium ions onto organo nanoclay loaded with 1-(2-pyridylazo)-2-naphthol (PAN). Thallium ions were quantitatively retained on the column in the pH range of 3.5–6.0, whereas quantitative desorption occurs with 5.0?mL of 5% ascorbic acid and thallium was determined by flame atomic absorption spectrometry. Linearity was maintained between 0.66?ng?mL^?1–15.0?µg?mL^?1?in initial solution. Detection limit was 0.2?ng?mL^?1?in initial solution and preconcentration factor was 150. Eight replicate determinations of 2.0?µg?mL^?1 of thallium in final solution gave a relative standard deviation of ±1.48%. Various parameters have been studied, such as the effect of pH, breakthrough volume and interference of a large number of anions and cations and the proposed method was used to determine thallium ions in water and standard samples. Determination of thallium ions in standard sample showed that the proposed method has good accuracy.     

Spectrophotometric Determination of Cadmium(II) Using p,p′‐Dinitro‐SYM‐Diphenylcarbazid in Aqueous Solutions

Abstract

A sensitive and selective spectrophotometric method is proposed for the rapid determination of cadmium(II) using, p,p′‐dinitro‐sym‐diphenylcarbazid, directly in aqueous solution. The reaction between cadmium(II) and p,p′‐dinitro‐sym‐diphenylcarbazid occurs immediately in strong basic media (0.02 N sodium hydroxide solution). The complex shows a maximum of absorption at 630–640 nm, and the absorbance remains stable for at least 24 h. The method allows the cadmium determination over the range 0.5–6.0 µg mL^?1, with a molar absortivity of 2.05×10⁴ L mol^?1 cm^?1 and features a detection limit of 0.13 ppm. The interferences caused by several ions [Ca(II), K(I), Ba(II), Al(III), Pb(II), Zn(II), Cl^?1, NO₃ ^?, SO₄ ^2?], which are present in most of environmental samples, were determined. The validation of the spectrophotometric method was done by recovery test of cadmium(II) in tap water and sea water. The results show that the proposed method has been successfully applied to the determination of cadmium(II) in water samples.     

An improved spectrophotometric determination of manganese(II) with 1-(2-quinolylazo)-2,4,5-trihydroxybenzene with applications to medicinal plants and chemical reagents

The effects of organic solvent, time and temperature on the colour-forming reaction are described. For nine solvents tested, the molar absorptivities were in the range 2.0×10⁴?6.7×10⁴ mol^?1 cm^?1; best sensitivity was obtained with a 1:1 water/2-propanol solution after a standing time of 35 min; temperature should be controlled to ±2°C. Beer's law was obeyed for 0–1.45 μg ml^?1 Mn(II). The improved method was applied to determinations of manganese(II) in various herbs and chemical reagents; the values found were in the range 5.4–48.4 μg g^?1 in herbs, and 0.001-0.012% (w/w) in reagents.     

2-取代氨基-6-甲基-5-氧代-4-正丁基-4,5-二氢-1,2,4-三氮唑并[1,5-a]嘧啶类衍生物的合成

以2-溴丙酸甲酯、α,α-二氯甲基甲醚和胍唑为原料, 经缩合以及环化反应制得2-氨基-6-甲基-5-氧代-4,5-二氢-1,2,4-三氮唑并[1,5-a]嘧啶. 为了提高其在有机溶剂中的溶解性, 该化合物再同1-溴丁烷发生亲核取代反应得到了2-氨基-6-甲基-5-氧代-4-正丁基-4,5-二氢-1,2,4-三氮唑并[1,5-a]嘧啶, 然后与芳基醛和叔丁基异氰发生Ugi多组分反应, 合成了一系列具有潜在催吐活性的2-取代氨基-6-甲基-5-氧代-4-正丁基-4,5-二氢-1,2,4-三氮唑并[1,5-a]嘧啶类衍生物, 产品结构经质谱、核磁共振谱及元素分析确认.     

The spectrophotometric determination and solvent extrāction of osmium with o-(β-benzoylthiourido)benzoic acid as reagent

o-(β-Benzoylthiourido)benzoic acid is proposed as a spectrophotometric reagent for the determination of osmium. The brownish yellow complex formed is soluble in alcohol and in other organic solvents. The colour system obeys Beer's law from 3 to 18 p.p.m. of osmium at 410 mμ with an optimum range of 3–15 p.p.m., where the percent relative error per 1% absolute photometric error is 2.75%. A 1:1 complex is formed and the dissociation constant is of the order of 10^-5. With prior extraction of palladium as the axide complex with n-butanol, osmium can be separated from almost all ions, including those of platinum metals, by extraction witli ethyl acetate.