The influence of molecular geometry on the fluorescence spectra of biphenyl and the polyphenyls

The shapes of the fluorescence spectra of rigid solutions (in ethanol at 77 K) of biphenyl,p-terphenyl, andp-quaterphenyl are shown to depend on the wavelength of the exciting light: the spectral resolution enhances with increasing wavelength of excitation. These spectra are interpreted in terms of a model wherein the equilibrium configuration of the fluorescent state is planar, but that of the ground state deviates from planarity.Some other results reported in the literature are also discussed and it is concluded that the ground states of the singly and doubly charged ions of these molecules, as well as the lowest triplet states of the neutral molecules, are nearly planar.     

Determination of gossypol solubility

To improve the extraction of gossypol from the cotton seeds, the solubility of gossypol in different solvents and at different concentrations of micelles was studied. Petroleum ether, hexane, and extraction benzol were used as solvents. Model micelles were prepared from the cotton oil free of gossypol; concentration of micelles ranged from 0 to 50%. Pure gossypol was added to the micelles in the amount sufficient for formation of saturated solution. The solution was then heated to a temperature close to the boiling point of the respective solvent for 10 minutes. The undissolved gossypol was then filtered off, washed and degreased with petroleum ether, dried and weighed. The amount of dissolved gossypol was determined by the difference between the initial and remaining amounts. Solubility of gossypol in the micelles was found to rise with the increase in the oil content. The solubility grew with the increase in the boiling point of a solvent. At micelles concentrations of 0-25%, solubility of gossypol increased in proportion to the increase in oil concentration. Further increase in the concentration resulted in marked rise in solubility, which reached 2.83% in the pure oil.     

Spectrum and polarizability of polyphenyls in the Pariser-Parr-Pople approximation

The Pariser-Parr-Pople approximation is used to calculate the electronic structure, electronic absorption spectrum, and polarizability for biphenyl, terphenyl, and quaterphenyl. The self-consistent MO are taken as basis functions for the multiconfiguration approximation. The minimum number of singly excited configurations is included. Bond orders, bond lengths, transition energies, oscillator strengths, and wave functions of the excited states are given in that approximation. The results are compared with published data and, where possible, with experiment. Calculation of the -electron polarizability with allowance for configuration interaction is discussed. The agreement with experiment is satisfactory for all the characteristics calculated.     

Determination of the solubility of organic compounds

Summary Estimations of solubility are carried out by observing with a magnifying lens the substance while it is exposed to air laden with vapor of the solvent.

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Zusammenfassung Teilchen der Substanz werden auf einem schmalen Objektträger abwechselnd einem mit dem Dampf des Lösungsmittels beladenen und einem reinen Luftstrom ausgesetzt, während sie durch ein Vergrößerungsglas beobachtet werden. Der zur Verflüssigung erforderliche Zeitraum ist offen-kundig durch den Löslichkeitsgrad bedingt.

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Résumé Une petite particule de substance placée sur une petite lame porte-objet est soumise alternativement à un courant d'air chargé de la vapeur du solvant et à un courant d'air pur tandis qu'elle est observée à l'aide d'une loupe. Le temps nécessaire à la liquéfaction dépend évidemment du degré de solubilité de la substance.

     

Determination of polychlorinated biphenyl compounds in indoor air samples

A simple procedure for the determination of six non-coplanar polychlorinated biphenyls (PCBs) in medium volumes of indoor air is described. Samples are forced at 6 m3/h through a device consisting of a quartz filter connected to the end of a conventional solid-phase extraction cartridge containing 60 mg of functionalized styrene-divinylbenzene. PCBs retained on the sorbent are directly eluted with 2 ml of hexane. Those associated to airborne particulate matter are microwave extracted in 10 min using 15 ml hexane-acetone (1:1). The proposed procedure is favorably compared to the use of polyurethane cylinders for the concentration of PCBs in terms of solvent consumption and rapidity of the desorption step. Furthermore, the functionalized sorbent showed higher breakthrough volumes than Amberlite XAD-2 for PCBs in gas phase. Quantification limits between 2 and 40 pg/m3 were obtained for six PCBs (from di- to heptachlorobiphenyls) using GC-electron-capture detection.     

Determination of one compound in the presence of a single interference. Linear absorbances method

Summary The paper exposes the theoretical and experimental principles of an analytical procedure for the determination of one compound in the presence of another with an overlapping absorption spectrum, without the need to use any standard solutions of the latter. The proposed method was applied to the determination of binary mixtures of known composition in order to assess its accuracy and precision.     

Determination of rosuvastatin in the presence of its degradation products by a stability-indicating LC method

A forced degradation study was successfully applied for the development of a stability-indicating assay method for determination of rosuvastatin Ca in the presence of its degradation products. The method was developed and optimized by analyzing the forcefully degraded samples. Degradation of the drug was done at various pH values. Moreover, the drug was degraded under oxidative, photolytic, and thermal stress conditions. Mass balance between assay values of degraded samples and generated impurities was found to be satisfactory. The proposed method was able to resolve all of the possible degradation products formed during the stress study. The developed method was successfully applied for an accelerated stability study of the tablet formulation. The major impurities generated during the accelerated stability study of the tablet formulation were matches with those of the forced degradation study. The developed method was validated for determination of rosuvastatin Ca, and the method was found to be equally applicable to study the impurities formed during routine and forced degradation of rosuvastatin Ca.     

Determination of the solubility of organic compounds. II

Summary In general, solid particles liquify when they are exposed to air laden with the vapor of a liquid in which they are soluble. There are exceptions, however, which may be explained by assuming the formation of a solvate.

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Zusammenfassung Feste Teilchen verflüssigen sich im allgemeinen, wenn sie Luft ausgesetzt sind, die mit dem Dampf einer Flüssigkeit geladen ist, in der sie löslich sind. Es wurden aber Ausnahmen gefunden, die möglicherweise durch die Bildung von Solvaten erklärt werden können.

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Résumé Généralement, les particules solides se liquéfient si elles sont exposées à l'air chargé de la vapeur d'un liquide dans lequel elles sont solubles. Il existe cependant des exceptions que l'on peut expliquer en supposant la formation de solvates.

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On the occasion of the hundredth return ofFriedrich Emich's birthday.

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The authors wish to express their appreciation to ProfessorO. F. Steinbach for his suggestions and advice.     

Water solubility of regioselectively 2,3-O-substituted carboxymethylcellulose

A series of 2,3-O-carboxymethylcelluloses (CMC's), which are regioselectively substituted at the C-2 and C-3 position, were prepared and their water solubility was examined. It was found that the lower limit for the degree of substitution (DS) value of water-soluble 2,3-O-CMC is about 0.3. This value was almost the same as that of CMC prepared in a slurry of isopropyl alcohol/water with isopropyl chloroacetate and sodium hydroxide, showing that the uniform alkylation is rather important to convert cellulose into water-soluble derivatives.     

Determination and correlation of the solubility for diosgenin in alcohol solvents

Using a laser monitoring technique, the solubility of diosgenin in ethanol, 1-propanol, 1-butanol, isobutyl alcohol, tert-butanol, 1-pentanol, and iso-octyl alcohol was measured over the temperature range from (290.15 to 330.15) K at atmospheric pressure. Its corresponding (solid + liquid) equilibrium data will provide essential support for industrial design and further theoretical studies. From the experimental results, the solubility of diosgenin in ethanol, 1-propanol, 1-butanol, isobutyl alcohol, tert-butanol, 1-pentanol, and iso-octyl alcohol was found to increase with increasing temperature and decrease with the increase of the polarity of the alcohols solvents. The Apelblat equation, the ideal model and the λh equation were used to correlate the solubility values. The results showed that the three models mentioned above agreed well with the experimental data.     

Study by inverse gas chromatography of the solubility of rifabutin in water in the presence of cyclodextrin

Inverse gas chromatography was used to study the stability of rifabutin and cyclodextrin complexes in water. The thermodynamic mixing functions were determined in the system rifabutin?cyclodextrin?water. Addition of hydroxypropyl-β-cyclodextrin to rifabutin creates in water a thermodynamically stable complex, with the solubility of rifabutin in water thereby raised and this antibiotic made more bioavailable in curing of tuberculosis.     

Determination of phenol in the presence of sulfite (sulfur dioxide) by the 4-aminoantipyrine spectro-photometric method

The interference of sulfite (sulfur dioxide) with the 4-aminoantipyrine (4-AAP) spectrophotometric method for phenol is discussed for procedures without distillation, and with distillation in the absence and presence of copper(II) sulfate. Sulfite represses the color development in all these procedures. Without chloroform extraction, the maximum tolerable amounts of sulfite in the procedures without distillation, distillation without copper(II) sulfate, and distillation with copper(II) sulfate are 15, 10, and 20 mg/100 ml, respectively. For the extraction method, the limits are 4.0, 4.0, and 10 mg/ 100 ml, respectively. Copprer(II) sulfate catalyzes the air-oxidation of sulfite. Phenol can be determined in the presence of large amounts of sulfite by treating with sulfide to form polythionates and thiosulfate; excess of sulfide is removed with copper(II) sulfate, sulfuric acid is added, the phenol is distilled, and the 4-AAP method is applied. Improvements are made in the overall accuracy of the 4-AAP method.     

相溶解度法研究不同环糊精对丹皮酚的增溶作用

采用相溶解度法,通过测定丹皮酚在不同温度不同浓度的β-环糊精(β-CD)、羟丙基-β-环糊精(HP-β-CD)、羟乙基-β-环糊精(HE-β-CD)、取代度为4的磺丁基醚-β-环糊精(SBE4-β-CD)以及取代度为7的磺丁基醚-β-环糊精(SBE7-β-CD)中的溶解度,绘制相溶解度曲线,丹皮酚的溶解度均随5种环糊精浓度的增加而成线性增加,相溶解度曲线为AL型,说明丹皮酚与环糊精以1∶1包合,实验结果表明,5种环糊精对丹皮酚均有增溶作用且SBE7-β-CD的增溶效果最佳.