Development and Validation of an HPLC Method for Determination of Ceftiofur Sodium

An isocratic high-performance liquid chromatographic method has been developed for assay of ceftiofur sodium in drug substance and in sterile powder for injection. Chromatography was performed on a 250 mm × 4.6 mm, 5 μm particle, C₁₈ column with a 78:22 (v/v) mixture of 0.02 m disodium hydrogen phosphate buffer (pH adjusted to 6.0 with 85% orthophosphoric acid) and acetonitrile as mobile phase, at a flow rate of 1.0 mL min⁻¹. The separation was monitored by UV detection at 292 nm. Validation of the method for linearity and range, intra- and inter-day precision, accuracy, specificity, recovery, robustness, and limits of quantification and detection yielded good results. The calibration plot was linear from 20.0–120.0 μg mL⁻¹ and the correlation coefficient was 0.9999. It was shown that ceftiofur was degraded under acidic, alkaline, oxidative, and photolytic conditions. The method was found to be stability-indicating and could be used for routine analysis of ceftiofur sodium for injection.     

Dimorphie von SrTa4O11 - ein Schritt von der tetragonalen Bronzestruktur zur Struktur von CaTa4O11

Dimorphism of SrTa₄O₁₁–a Step from the Tetragonal Structure of Bronzes to the Structure of CaTa₄O₁₁ Hexagonal SrTa₄O₁₁ is a new modification and isostructural with CaTa₄O₁₁. It was obtained by heating the already known SrTa₄O₁₁ in a chlorine atmosphere at 1000–1100°C. The Guinier powder pattern could be indexed with the following hexagonal unit cell: a = 6.25 Å; c = 12.33 Å. In air at 1180°C SrTa₄O₁₁(hex.) changes into the well-known TTB-modification (corresponding to the tetragonal tungsten bronzes). The transition of SrTa₄O₁₁(TTB) to SrTa₄O₁₁(hex.) was only observed in the presence of a transporting agent (Cl₂) or a mineralizer (melt of B₂O₃) at temperatures below 1100°C. This transition could not be achieved by means of a solid state reaction. In a (Ca, Sr) Ta₄O₁₁ solid solution with at least 78 At.-% Ca the hexagonal form could be stabilized even at temperatures where otherwise the TTB-modification occurred.     

Primary yields of CH3O and CH2OH radicals resulting in the radiolysis of high purity methanol

The triethylsilane radical R₃^•Si, produced by radiolysis in an airfree methanol/silane-system, acts as a specific scavenger for the CH₃^•O and ^•CH₂OH transients with rate constants, k₁₄(R₃^•Si + CH₃^•O) = 1.1 x 10⁸ dm³ mol^-1s^-1 and k₁₅(R₃^•Si + ^•CH₂OH) = 0.7 x 10⁸ dm³ mol^-1s^-1, resulting in R₃Si—OCH₃ (triethylmethoxysilane) and R₃Si—CH₂OH (triethylsilylmethanol). By increasing the silane concentration (range: 10^-2-6 mol dm^-3 R₃SiH) the formation of the otherwise major products of methanol radiolysis, formaldehyde and glycol, is successively reduced to nil. The yield of R₃Si—CH₂OH, studied under the same conditions, passes a maximum at about 0.8 mol dm^-3 R₃SiH and then also diminishes. On the other hand, the yield of R₃Si—OCH₃ is increased correspondingly and reaches an interpolated value of G = 3.75 ± 0.1 at 4 mol dm^-3R₃SiH. This indicates that the radical CH₃^•O (G = 3.75 ± 0.1) is the primary radiolytic transient of methanol in addition to H, e^-_sol etc., but not ^•CH₂OH species. The latter one is obviously formed by the secondary reaction: CH₃^•O + CH₃OH→ CH₃OH + ^•CH₂OH.     

Investigation of minerals and of lunar samples (14163, 14258) by simultaneous thermal and X-ray analysis

Summary A new thermoanalytical technique Thermo-Molecular Beam Analysis (TMBA) is described which one allows to continuously follow the weight change in the sample by measurement of its gaseous reaction products, which are analysed simultaneously by mass spectrometry. In addition, the X-ray powder pattern of the sample is recorded at the same time as a function of temperature. Only small, 3–10 mg, samples are needed. The various applications and the information on reaction kinetics which can be obtained with the TMBA-method are discussed in detail for three examples: crystallization of lunar glass, thermal decomposition of Ni-oxalate dihydrate and of calcite. One of the main advantages of this new method is the possibility to follow not only the kind and concentration of gases which are evolved during a reaction, but also to identify the solid reaction products, especially metastable phases, and thermal expansion characteristics.

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Simultane thermogravimetrische und röntgenographische Untersuchung von Mineralien und Mondgesteinsproben (14163, 14258)

Zusammenfassung Eine neue thermoanalytische Methode Thermo Molecular Beam Analysis (TMBA) ermöglicht die kontinuierliche Messung der Gewichtsveränderungen einer Probe über die bei der Zersetzung eines Stoffes abgegebenen gasförmigen Reaktionsprodukte. Neben der gleichzeitigen massenspektrometrischen Analyse wird zusätzlich simultan das Röntgenpulverdiagramm der Probe in Abhängigkeit der Temperatur aufgenommen. Die dabei benötigten Probenmengen sind verhältnismäßig sehr gering (3–10mg). Die vielseitigen Anwendungsmöglichkeiten sowie die speziellen Informationen über reaktionskinetische Details dieser Methode sind an Hand von mehreren Beispielen ausführlich diskutiert: Thermischer Abbau von Nickeloxalat-Dihydrat, Zersetzung von Calcit und Kristallisation von Mondgläsern. Der wesentliche Vorteil dieser Methode ist, daß nicht nur die Art und die Menge der abgegebenen Gase während des Reaktionsablaufes kontinuierlich registriert werden, sondern auch die Änderungen im Ausgangsprodukt, d.h. der festen Reaktionsprodukte, vor allem metastabile Zwischenphasen und das thermische Ausdehnungsverhalten beobachtet werden können.

Results on lunar samples were presented at the Third Lunar Science Conference, 10.1.–13.1.1972 in Houston, Texas, U.S.A.     

Laser micro mass analysis of bulk polymeric samples

Laser micro mass spectrometry (LAMMS) was used for organic micro-analysis of bulk polymeric samples with a lateral resolution of about 3 m. The experiments were performed with a LAMMA 1000 instrument which was modified by the addition of a transmission illumination system for the observation of thin sections and a heating/cooling sample stage with sample transfer lock. It was found that crystallites or agglomerates of low-molecular-weight compounds could be identified by both molecular ions and characteristic fragments, and cyclic oligomers in bulkpolyamide 6 could be detected as cationized species if cations were present in the sample. On the other hand, the identification of high-molecular-weight polymers, e.g., in inclusions, was based on structurally significant fragments of the repeat unit. For samples with a low absorbance at the laser wavelength used, this fragment ion yield could be maximized by evaporating a thin absorbing layer onto the sample surface. If thin sections could be prepared from a sample a micro-FTIR analysis was possible. Such experiments gave results which were complementary to those of the corresponding LAMMS analysis.     

Efficient cellulose solubilization by a combined cellulosome-β-glucosidase system

The cellulosome, the multienzyme complex of the cellulase system ofClostridium thermocellum, that mediates the solubilization of insoluble cellulose, is strongly inhibited by the major end product, cellobiose. By combining a purified β-glucosidase fromAspergillus niger with the cellulosome, accumulated cellobiose was hydrolyzed thereby resulting in a dramatic enhancement (up to 10-fold) of cellulose degradation. The observed enhancement was expressed both in the rate and degree of solubilization of microcrystalline cellulose, compared with that observed for the unsupplemented cellulosome. Near-complete conversion of cellulose to glucose could be obtained from dense substrate suspensions (up to at least 200 g/L).     

Titan

Ohne Zusammenfassung