Electrochemical detection of tryptophan metabolites following high-performance liquid chromatography.

Electrochemical detection of tryptophan metabolites following separation on a reversed-phase high-performance liquid chromatography column was compared with other means of detection. Of 29 compounds studied, 26 could be detected at a sensitivity comparable to that of fluorescence derivatisation procedures. Response was linear over a wide range of concentrations and selectivity was shown to be superior to ultraviolet detection when analysing urine. Additionally, it was possible to control selectivity so that only those tryptophan metabolites from the tryptophan hydroxylase pathway were detected. This is of particular value in the study of distrubances of serotonin metabolism and is unique to this type of detector.     

Catalysts for the determination of oxygen in organic compounds

Summary Thermal decomposition of metal-organic complexes of nickel, cobalt and iron has given catalysts which are very effective at about 900° for the conversion of carbon dioxide, water and other oxygencontaining sample decomposition products to carbon monoxide in the direct determination of oxygen in organic compounds when using a modified Unterzaucher type apparatus. A copper catalyst similarly prepared required a temperature of 1030° whereas a manganese complex decomposition product was ineffective.

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Katalysatoren zur Sauerstoffbestimmung in organischen Substanzen

Zusammenfassung Durch thermische Zersetzung metallorganischer Komplexe von Ni, Co und Fe erhält man Katalysatoren, die die Umwandlung von CO₂, H₂O und anderen sauerstoffhältigen Zerfallsprodukten zu CO bei etwa 900° C bei der direkten Sauerstoffbestimmung in einer modifizierten Unterzaucher-Apparatur sehr wirksam fördern. Ein ähnlich hergestellter Cu-Katalysator erfordert 1030° C und das Zersetzungsprodukt eines Mn-Komplexes ist unwirksam.

     

Coumarins fromPhlojodicarpus sibiricus

Phlojodicarpin [8-(2,3-epoxy-1-hydroxy-3-methylbutyl)-7-methoxycoumarin, C₁₅H₁₆O₅, mp 143–145°C, [] _D ²⁵ -37.5°], and isophlojodicarpin [8-(1,2-epoxy-3-hydroxy-3-methylbutyl)-7-methoxycoumarin, C₁₅H₁₆O₅, mp 132–134°C, [] _D ²⁵ -102.5°] have been isolated from the epigeal part ofPhlojodicarpus sibiricus. The results of the IR, UV, PMR, and mass spectrometry of these compounds are given.Institute of Chemistry, Academy of Sciences of the Mongolian Peoples' Republic, Ulan-Bator. Irkutsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 47–49, January–February, 1981.     

The preparation of hot-pressed chalcogenide spinels. II. Stoichiometry and optical transparency in CdCr2S4 and CoCr2S4

The compounds CdCr₂S₄ and CoCr₂S₄ have been hot pressed into disks that are highly transparent in the infrared. Stoichiometry has been altered by varying the $\text{Cr}{}^{\mathrm{3+}}\text{M}{}^{\mathrm{2+}}$ ratio, where M²⁺ is Cd²⁺ or Co²⁺. The effects of nonstoichiometry on optical transmission were determined. Excess M²⁺ attenuates the transmission much more than excess Cr³⁺.     

Determination of traces of perchlorate in chlorate solutions

Perchlorate present in chlorate solutions is determined gravimetrically as tetraphenylphosphonium perchlorate after destruction of chlorate by addition of hydrochloric acid. Interference of Fe(III) and Cr(III) is prevented by complexing with tarartic acid. Replicate analyses of a sodium chlorate solution containing NaClO(3), NaCl, Na(2)Cr(2)O(7), and 390 ppm NaClO(4) showed 405 ppm NaClO(4) (standard deviation 19 ppm, 12 results).     

Synthesis of 4-alkyl-substituted 1,2,3,4-tetrahydropyrimidin-2-ones by the Biginelli reaction

p-Toluenesulfinic acid is an effective catalyst for condensation of acetoacetic ester with urea and aliphatic or aromatic aldehydes, leading to formation of 4-substituted 6-methyl-5-ethoxycarbonyl-1,2,3,4-tetrahydropyrimidin-2-ones.M. V. Lomonosov State Academy of Fine Chemical Technology, Moscow 117571, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 979–982, July, 1998.     

Pyrimidines

The condensation of -substituted acetophenones with benzylidenebisurea in an acid medium has given 5-R-2-oxo-4,6-diphenyl-1,2,3,4-tetrahydropyrimidones. The analogous condensation of propiophenone forms 5-methyl-2-hydroxy-4,6-diphenylpyrimidine. The tetrahydro derivatives obtained are readily dehydrogenated to 5-R-2-hydroxy-4,6-diphenylpyrimidines.For part XX, see [1].     

A pharmaceutical information manager's viewpoint on R & D information resource management

An overview of the environment (from my perspective) related to information resource management in pharmaceutical R & D has been presented. Some notions of organizational preference (functional), employee selection (chemist turned information scientist), automation (user friendly, cost effective), and the value of project teams (information transfer) have been noted. Difficulties associated with keeping our innovative tools sharp were observed. Finally, we noted that our bottom line--productivity--should first consider what is useful (effectiveness) and then learn how to do it well--efficiency. Success in the management of information resources depends on the proactive delivery of information packets which find their way into problem solving and decision support for scientists or line managers.     

Photoionization of the Ar2 dimer

The relative photoionization cross section for Ar₂ was measured in the wavelength region 820–860 Å. The spectrum shows detailed autoionization structure throughout this region with no contribution from direct ionization. The appearance potential of Ar⁺₂ corresponds to 856.5 ± 1.5 Å.     

Water-soluble copolymers. XXV. Ion-binding studies of N-substituted acrylamide copolymers using potentiometric and spectroscopic methods

Spectroscopic and potentiometric methods have been used to study the ionic properties of several N-substituted acrylamide copolymers that display unusual ion-binding character. The ionic groups and the amide groups (both on the same repeating unit and on adjacent acrylamide units) in the copolymers are found to chelate calcium ions. The stabilizing effect of this amide chelation is found to be dependent on copolymer composition. A model is proposed to explain the unusual binding behavior of the acrylamide polymers. This involves the formation of an intramonomer chelate or one with neighboring acrylamide units that prevent precipitation of the polymers.