Determination of the immunosuppressive drug tacrolimus in its dosage forms by high-performance liquid chromatography

Summary A high-performance liquid chromatographic (HPLC) method has been developed and validated for the determination of FK506, a new immunosuppressant, in bulk drug samples and dosage forms. Equilibration between FK506 (I) and its tautomeric compounds (II and III) was accomplished artificially in water-dehydrated alcohol (11) employed as an extraction solvent. After reaching equilibrium, separation of I, treated as the representetive of equilibrated FK506, from its related substances was achieved by reversed-phase HPLC on a C₁₈ column with water-isopropyl alcohol-tetrahydrofuran (522, v/v) as the mobile phase, and detection at 220 nm. Component I in dosage forms could be recovered satisfactorily and determined with good precision. The calibration graph was linear over the range 2–6 g for I.     

Trennung, Nachweis und Bestimmung von Benzidin, α- und β-Naphthylamin

Summary Three methods (photometry, TLC, HPLC) are proposed for the separation, detection and determination of the cancerogenic compounds benzidine, - and -naphthylamine in drinking water. The necessary detection limit of 0.1 g/l has been achieved.     

New instruments and methods for enthalpimetric analysis and calibration

A review is given of recently developed instruments used in thermometric analysis and new methods of direct injection enthalpimetry.In the past two years, several types of Tronac (Orem, Utah) and Setaram (Lyon, France) calorimeters have been developed. A new mixing cell construction led to development of a flow instrument for automated thermometric analyses (Technicon, Tarrytown N. Y.). A new type of Hungarian instrument, Ditermanal (Orion, Budapest) permits arbitrary analyses.At the Technical University in Brno, small table twin isoperibol instruments allowing the direct analyses of solid samples have been developed. The use of PTC thermistors and a calibration device improved the accuracy of measurements.Many new methods of silicate and lime analysis, water determination, etc. have been elaborated.

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Zusammenfassung Eine Übersicht über die zur thermometrischen Analyse eingesetzten, entwickelten Instrumente und neuen Methoden der Direkt-Injektion Enthalpimetrie wird gegeben.In den zwei vergangenen Jahren wurden verschiedene Kalorimetertypen TRONAC (Orem, Utah) und SETARAM (Lyon, France) entwickelt. Eine neue Mischzellenkonstruktion ermöglichte es ein Durchflussinstrument für automatische thermometrische Analysen (TECHNICON, Tarrytown, N. Y.) zu entwickeln. Ein neuer ungarischer Instrumententyp, DITERMANAL (ORION, Budapest), ermöglicht die Durchführung von Schiedsanalysen.An der Technischen Universität Brno wurden kleinen Zwillings-Isoperibol-Tisch Instrumente entwickelt, welche auch die direkten Analysen fester Proben ermöglichen. Der Einsatz von PTC-Thermistoren und einer Eichvorrichtung erhöhte die Messgenauigkeit.Viele neue Methoden der Silikat- und Kalkanalyse, Wasserbestimmungen usw. wurden erarbeitet.

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Résumé On passe en revue les instruments récemment mis au point et utilisés en analyse thermométrique ainsi que les nouvelles méthodes d'enthalpimétrie par injection directe.Dans les deux dernières années, divers types de calorimètres ont été mis au point: TRONAC (Orem, Utah) et SETARAM (Lyon, France). La réalisation d'une nouvelle cellule de mélange a permis de mettre au point un appareil à flux pour les analyses thermométriques automatiques (TECHNICON, Tarrytown, N. Y.). Un nouveau type d'instrument hongrois, DITERMANAL (ORION, Budapest) permet d'effectuer des analyses arbitrales.A l'université technique de Brno de petites tables instruments jumeaux isopériboliques permettant aussi d'effectuer des analyses directes des corps solides ont été réalisés. L'application de thermistors PTC et un dispositif pour l'étalonnage augmentent l'exactitude des mesures.Des méthodes nouvelles nombreuses pour l'analyse des silicates, des pierres calcaires, de l'eau, etc., ont fait l'objet d'études.

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, . (, ) (, ). (H, , -). (, ) . , . . , , .

     

On the interpretation of differences in mechanisms, kinetics and dynamics of oxidation reactions on metal and oxide catalysts

Langmuir-Hinshelwood type mechanisms with competitive adsorption are suggested to be more typical for metal catalysts, since, unlike on oxide systems, oxidizable substance and molecular oxygen can be adsorbed on the same (reduced) active sites. Therefore, multiple steady states and critical phenomena are more characteristic for catalysis on metals.

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, - , , () . .

     

Catalytic properties and phase composition of multicomponent catalysts for oxidative ammonolysis of propane

Studies of the phase composition and catalytic properties of several complex oxide catalysts for oxidative ammonolysis of propane indicate that the active phases of these catalysts are antimonates of the respective metals. Phosphorus and tungsten additives to the catalysts promote the formation of such phase compositions, i.e. the formation of antimonates and the binding of excess antimony oxide.

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. , ; , .

     

State of copper ions, bond energy of oxygen and catalytic properties in hydrogen oxidation for a copper-magnesium system

The bond energy of surface oxygen in a copper-magnesium catalyst and its reactivity are shown to be greatly dependent on the structure of the nearer environment of copper ions. For catalysts prepared at low temperatures (773 K) this structure changes from a symmetrical square planar in CuO to an octahedral with various degrees of axial distortion depending on the copper content.

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, . , (773 ), CuO .

     

Oxidation of ethylene to ethylene oxide: A tpr study on fresh and aged catalysts

The deactivation of a silver catalyst was investigated after six years of industrial production of ethylene oxide. Temperature-programmed reduction was used to characterize the chemical nature of the silver and its reactivity towards oxygen. The fresh and some aged catalysts were examined, also after different thermal treatments.During the industrial run, the surface species were modified and some oxygen diffused into the bulk of the metal. Aging caused permanent changes in the characteristics of the silver, resulting in a different interaction with oxygen. The TPR spectra exhibited a trend along the reactor axis, suggesting a correlation with the degree of deactivation of the catalyst.

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Zusammenfassung Die Desaktivierung eines Silberkatalysators wurde nach 6-jährigem Einsatz zur industriellen Produktion untersucht. Temperaturprogrammierte Reduktion wurde angewandt, um die chemische Natur des Silbers und dessen Reaktivität gegenüber Sauerstoff zu charakterisieren. Frische und einige gealterte Katalysatoren wurden nach verschiedenen thermischen Vorbehandlungen untersucht. Die Alterung verursachte bleibende Veränderungen in charakteristischen Eigenschaften des Silbers, was in der unterschiedlichen Wechselwirkung mit Sauerstoff zum Ausdruck kommt. Die TPR-Resultate zeigen einen Trend entlang der Reaktorachse, was auf eine Korrelation mit dem Grad der Desaktivierung des Katalysators hindeutet.

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. () . , , . . , , . , .

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The experimental contributions by F. Genoni and G. Valassina are gratefully acknowledged.     

Oxidation of ethanol on platinum/alumina and copper oxide catalysts

The oxidation of ethanol on CuO, CuO/Al₂O₃ and Pt/Al₂O₃ catalysts has been studied at various concentrations of alcohol, oxygen and water vapor in the reaction mixture. The reaction order and activation energies have been determined for both complete and partial oxidation processes. A consecutive oxidation scheme is suggested.

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CuO, CuO/Al₂O₃ Pt/Al₂O₃ , . . .

     

ESR measurements of concentration for strong surface acceptor centers on zeolites and Al2O3 using nitroxide radical TEMPON

A method to measure concentrations of strong surface acceptor centers on aluminosilicate catalysts by their titration with a solution of TEMPON (2,2,6,6-tetramethyl-4-oxypiperidine-1-oxyl) is suggested. The concentration of these centers corresponds to that of CO test molecules for the strongest acceptor centers (_CO 2210 cm^–1) obtained using IR spectroscopy. It is shown that for ZSM-5 zeolites most of these centers are localized on their external surface.

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. - - CO (_CO 2210 cm^–1). , ZSM-5 .

     

Ammoxidation of propylene over binary and ternary mixed oxides of Bi, Sb and Sn

The ammoxidation of propylene has been investigated at 673 K in a pulse reactor over binary and ternary oxide mixtures of SnO₂, Sb₂O₄ and Bi₂O₃. While the oxidation activity of these catalysts stems from the presence of Sn and Bi, the selectivity is attributed mainly to Sb. In the case of some ternary oxides, 4-methyl-pent-2-enonitrile could be observed among the oxidation products, proving that dimerization of propylene may occur under ammoxidation conditions.

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673 SnO₂, Sb₂O₄ Bi₂O₃. Sn Bi, , , Sb. B 4---2-, .

     

Adsorption and hydrogenation of unsaturated aldehydes over rhodium black

Hydrogenation selectivity of conjugated ethylenic bonds of unsaturated aldehydes over rhodium black is shown to be determined by intramolecular interactions in surface complexes due to the electronic structure of the initial unsaturated aldehydes.

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- , .

     

Formation and thermal decomposition of silicon oxynitride compounds. Part III

The formation of a previously unknown compound with stoichiometry Li₆SiN₂O₂ was found during studies on the reactivity of Li₂SiN₂ with Li₂O, of SiO₂ with Li₃N and of Li₃SiNO₂ with Li₃N.

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Zusammenfassung Die Bildung einer bisher unbekannten Verbindung der Stöchiometrie Li₆SiN₂O₂ wurde bei Untersuchungen der Reaktivität von Li₂SiN₂ mit LiO, von SiO₂ mit Li₃N und von Li₃SiNO₂ mit Li₃N beobachtet.

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Li₆SiN₂O₂ Li₂SiN₂ , , Li₃SiNO₂ .

     

Reactivity of aromatic nitrons with alkyl and alkylperoxyl radicals

The catalytic properties of Mn(II)-histidine complexes for the oxidation of indigo carmine by H₂O₂ have been studied. It has been shown that the complex Mn(II) (Histidine)₂ existing in as a dimer is the true catalyst but at high concentration of the reactant the reaction is inhibited because of complex formation between the reactant and the catalyst.

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Mn(II)- . , Mn(II)·()₂ . , .

     

Collisional energy transfer in the decomposition of 2-methyloxetane and 3-methyloxetane, I. Gas/gas collisions

The pressure dependence of the unimolecular rate constants for the thermal decomposition of 2-methyloxetane and 3-methyloxetane has been studied. The average energy transferred downward in gas-gas collision was determined by the application of RRKM theory and a stepladder model of energy transfer.

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2- 3-. , - , .

     

Individual and combined oxidation of CO and SO2 on vanadium catalysts with and without Pd additives

The function of SO₂ in CO oxidation on Pd-V catalysts is to transform a rapid heterogeneous-homogeneous process to a slower heterogeneous one. High concentrations of CO also exert the same effect. In the heterogeneous process an increase in the SO₂ concentration increasing the degree of catalyst reduction with and without Pd additives, promotes CO oxidation.

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CO - SO₂ - . CO. SO₂, , , CO.

     

Valence states and solubility limits in ternary iron-tin-antimony mixed oxide catalysts

The electrical conductivity study of a series of ternary Fe–Sn–Sb mixed oxides with 5 at. % Fe has shown that iron dissolves in the structure of SnO₂ as ferric ions and, consequently creates acceptor centers which compensate the doping effect of Sb⁵⁺ ions simultaneously dissolved, thus increasing the maximum dissolution of pentavalent antimony and shifting thereby the apparition limit of Sb³⁺ ions towards higher Sb contents.

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Fe–Sn–Sb c 5 . %- Fe , SnO₂ , , Sb⁵⁺, . , Sb³⁺ Sb.

     

Hydroxylation selectivity of phenol and O-protected phenols in the Fe(III)-catechol-H2O2 system

Oxidation selectivity of phenol and its O-protected derivatives in the Hamilton system has been studied. Modification of OH groups by acyl substituents and addition of -cyclodextrin markedly enhance paraselectivity of this reaction.

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O- . , OH- - - .

     

Kinetics of phase transformations in Cu-Al and Cu-Zn-Al alloys

The non-isothermal kinetics of the solid-state reactions taking place in Cu-Al and Cu-Zn-Al alloys were studied by DTA and X-ray measurements. It was found that the degree of conversion, which represents the change in the reacting system, is a function of the area increase in the DTA peak. The kinetic analysis shows that DTA is a useful method for the study of formal kinetic laws. From thef() functions, conclusions on the mechanism of the phase transformations can be drawn.

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Zusammenfassung Die nicht-isotherme Kinetik von in Cu-Al und Cu-Zn-Al-Legierungen verlaufenden Festkörperreaktionen wurden mittels DTA und Röntgenmessungen untersucht. Es wurde festgestellt, daß die Zunahme der Fläche des DTA-Peaks abhängig von dem die Veränderungen im Reaktionssystem repräsentierenden Konversionsgrad ist. Die kinetische Analyse zeigt, daß die DTA eine nützliche Methode zur Untersuchung der formalen kinetischen Gesetzmäßigkeiten ist. Aus den Functionenf() können Schlußfolgerungen hinsichtlich des Mechanismus der Phasenübergänge gezogen werden.

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, Cu-Al Cu-Zn-Al. , , , . . f() .

     

Effects of copolymers modifying PVC and of mixing ability of components in thermal dehydrochlorination and decomposition of blends

The thermal dehydrochlorination and decomposition in air and in nitrogen of films made of PVC and blends of PVC and VC/VAC, MBS, MMA/MA or ABS were studied. Both processes take place at higher temperature in air than in nitrogen. In air, ABS and MMA/MA cause an apparent increase in the decomposition temperature of PVC, whereas in nitrogen these copolymers accelerate its decomposition.The influence of modifying copolymers on the thermal dehydrochlorination and decomposition of PVC depends not only on the type, but also on the quantity of copolymer.Small amounts of modifying copolymers in samples affect their thermal stability in the opposite way to larger contents of the copolymers. This shows that the structure of films with an incompatible mixture of PVC and copolymers plays the major role in the degradation processes.

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Zusammenfassung Die thermische Dehydrochlorierung und die Zersetzung von aus PVC und Gemischen von PVC mit VC/VAC, MBS, MMA/MA oder ABS hergestellten Filmen wurden in Luft- und StickstoffatmosphÄre untersucht. Beide Prozesse verlaufen in Luft bei höheren Temperaturen als in Stickstoff. In Luft verursachen ABS und MMA/MA eine scheinbare Erhöhung der Zersetzungstemperatur von PVC, in Stickstoff jedoch beschleunigen diese Kopolymeren die PVC-Zersetzung. Die Beeinflussung der thermischen Dehydrochlorierung und der Zersetzung von PVC durch modifizierende Kopolymere hÄngt nicht nur von der Natur, sondern auch von der Menge des Kopolymeren ab. Kleine Mengen von modifizierenden Kopolymeren beeinflussen die thermische StabilitÄt gerade in entgegengesetzter Weise wie grö\ere. Es scheint, da\ die Struktur der Filme mit inkompatiblen Mischungen von PVC und Kopolymeren in den Degradationsprozessen die Hauptrolle spielt.

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/, , / . , . / , . , . . , .

     

Investigation of surface phenomena on solid catalysts by simultaneous thermogravimetry and DTA

Thermogravimetry and simultaneous DTA were used to investigate the phenomena of adsorption, desorption and surface reactions on solid catalysts. The measurements were carried out with NaX and X-type ion-exchanged zeolites and silica-alumina gels (Ketjen) treated with sodium hydroxide in the presence of carbon dioxide. On the basis of the quantitative results it is possible to give an interpretation of the surface phenomena and to establish the existence of various active centres on the surfaces of the catalysts. In the case of the adsorption of carbon dioxide on X-type zeolites, the quantity of carbon dioxide adsorbed is much smaller on ion-exchanged zeolites than on NaX.

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Zusammenfassung Thermogravimetrie und simultane DTA wurden zur Untersuchung der Adsorptions-, Desorptions-Erscheinungen und Oberflächenreaktionen an festen Katalysatoren eingesetzt. Die Messungen wurden and NaX und Zeolithen des Typs X sowie an Silika-Aluminiumoxidgelen Ketjen durchgeführt, welche mit Natriumhydroxid in Gegenwart von Kohlendioxid behandelt worden waren. Aufgrund der quantitativen Ergebnisse ist es möglich eine Deutung der Oberfiächenerscheinungen zu geben und die Existenz verschiedener aktiver Zentren an der Katalysatorenoberfläche nachzuweisen. Im Falle der Adsorption von Kohlendioxid an Zeolithen des Typs X ist die Menge des adsorbierten Kohlendioxids am Ionenaustauscher viel niedriger als am NaX.

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Résumé Application de la TG et de l'ATD simultanées à l'étude des phénomènes d'adsorption, de désorption et de réactions de surface sur des catalyseurs solides. Les mesures ont été effectuées avec des zéolites échangeuses d'ions de type NaX et X ainsi qu'avec des gels Ketjen silice-alumine traités par NaOH en présence de CO₂. Les résultats quantitatifs permettent de donner une interprétation des phénomènes de surface et d'établir l'existence de divers centres actifs à la surface des catalyseurs. Dans le cas de l'adsorption de CO₂ sur les zéolites de type X, la quantité de CO₂ adsorbé est beaucoup plus faible que sur les zéolites de type NaX.

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DTA , . - NaX X - « », . . X, - , NaX.