Analyse organique fonctionnelle: Analyse thermogravimétrique des dinitro-2,4 phénylhydrazones

The authors have traced and studied the thermolytic curves of 2,4-dinitrophenyl-hydrazones of 14 aldehydes and of 19 ketones with regard to their use in gravimetric analysis.     

Source à impulsion de puissance élevée. Etudes préalables en vue du dosage des halogènes

For determining halogens with the aid of a high-power pulsed source a preliminary study is required in order to choose the polarity of the sample so that the highest possible detection power is achieved. Our study concerned the effects of temperature and background intensity on the detection power.     

Quelques facteurs importants en thermogravimétrie

Résumé Les auteurs rappellent l'importance de certains facteurs expérimentaux en thermogravimétrie: vitesse d'échauffement et masse de la substance échantillon, contrôle et analyse de l'atmosphère du tube laboratoire, nature et forme du creuset. Ils montrent ainsi les avantages consécutifs à la diminution de la prise d'essai jusqu'aux valeurs du milli- ou même du microgramme, dans le cas des produits purs.

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Summary The authors point out the importance of certain experimental factors in thermogravimetry: rate of heating and weight of the sample taken, control and analysis of the laboratory tube, nature and shape of the crucible. They thus show the consecutive advantages residing in the diminution of the size of the sample to values in the milli- or even the microgram range in the case of pure products.

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Zusammenfassung Die Verfasser heben die Bedeutung gewisser experimenteller Umstände bei der Thermogravimetrie hervor: die Geschwindigkeit der Temperatursteigerung, die Masse der Probe, die analytische Kontrolle der Laboratoriumsatmosphäre, Art und Form des Tiegels. Sie weisen auf die Vorteile der Verkleinerung der Einwaage bis zur Größenordnung von 10^–3 bis 10^–6 g bei reinen Produkten hin.

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Extraits de la conférence présentée lors duSymposium international sur l'Analyse Thermique à laNorthern Polytechnic, Londres, 13–14 Avril 1965.     

LC–MS/MS quantification of ractopamine in bovine and swine muscle: stability of matrix-matched calibration solutions

Accreditation and Quality Assurance - Ractopamine is used as an animal feed additive, but its adverse effects led to the necessity of the current monitoring programs of ractopamine residues in food...     

Study of the thermal behavior of bicuíba oil (Virola bicuhyba)

Bicuíba belongs to the Virola bicuhyba (Schott ex Spreng.) Warb species, Miristicaceas (Myristicaceae) family, which is frequently found in the Atlantic Forest of South and Southeast Brazil. Extraction of the Bicuíba oil was carried out and characterized by gas chromatography. The composition of in nature of this oil indicates that there is a predominance of saturated fatty acids with ~35 % lauric acid and ~40 % myristic acid. Details concerning the thermal behavior were evaluated by thermogravimetry, differential thermal analysis, and differential scanning calorimetry under oxygen and nitrogen atmospheres, showing thermal stability between 208 and 210 °C, respectively. Additionally, the kinetic studies were evaluated from several heating rates with a sample mass of 5 and 20 mg in open crucibles. The obtained data were evaluated with the isoconversional method kinetic, where the values of activation energy (E _a/kJ mol^?1) were plotted in function of the conversion degree (α).     

Preparation and Optical Properties of Novel 3-Alkoxycarbonyl Aza- and Diazacoumarins

A series of 14 new 3-alkoxycarbonyl 6-aza-, 7-aza-, and 6,8-diaza-coumarins was prepared using various strategies involving either a Knoevenagel or a Pechmann condensation reaction. The coumarin nucleus displays different reactive functional groups allowing straightforward derivatization. The optical properties of the new azacoumarins were measured in methanol.     

An S = 6 cyanide-bridged octanuclear FeIII4NiII4 complex that exhibits slow relaxation of the magnetization

The synthesis and structural and magnetic characterization of an S = 6 cyanide-bridged octanuclear FeIII4NiII4 (1) complex is described. Ac susceptibility and mu-SQUID measurements suggest that fast magnetization relaxation is present in zero-field due to quantum tunneling of the ground spin state (QTM) while application of small magnetic fields induces slow relaxation of the magnetization.