Spectrophotometric Determination of Tetracyclines in Pure Form and in Pharmaceutical Preparations,by a Molybdenum Blue Method

Abstract

A new and sensitive spectrophotometric method has been developed for the determination of tetracyclines either in a pure form or in Pharmaceuticals, by a molybdenum blue method. The procedure is based on the observation that, in sulphuric acid medium, tetracyclines reduce ammonium molybdate to molybdenum blue, the absorbance of which is proportional to the amount of antibiotic present. The variables affecting development of the color have been investigated and the conditions optimized. Beer's law is obeyed for up to 20 μg/ml of tetracycline HCl and oxytetracycline HCl, 28 μg/ml of demeclocycline HCl, 18 μg/ml of chlortetracycline HCl, 32 μg/ml of doxycycline HCl and 40 μ/ml of rolitetracycline. Molar absorptivities (1 mol^?1 cm^?1) and Sandell's sensitivities (μ cm^?2 per 0.001 absorbance unit) are, respectively: tetracycline HCl 4.9×10⁴ and 0.0098, oxytetracycline HCl 5.4×10⁴ and 0.0092, demeclocycline HCl 1.6×10⁴ and 0.0313, chlortetracycline HCl 5.5×10⁴ and 0.0094, doxycycline HCl 3.4×10⁴ and 0.0141, rolitetracycline 2.7×10⁴ and 0.0195.     

A New Colorimetric Reagent for Carbon Monoxide

Abstract

A new colorimetric reagent for carbon monoxide is described. The reaction sequence apparently involves reduction by carbon monoxide of [PdCl₄]^2-, which then reduces [Fe^III EDTA]^? to [Fe^IIEDTA]^2-. The latter undergoes ligand exchange with 2,2′-dipyridyl or 1,10-phenanthroline to form the more stable colored [FeL₃]²⁺, which is measured spectrophotometrically. Sodium molybdate enhances the overall reaction. The color intensity produced is non-linear but reproducible. The method is unique in that a soluble colored compound is produced rather than a metal sol.     

Solubilities and Ksp Values of the Less Soluble Anion Salts of “Nitron” (1,4-Diphenyl-3-anilino-1,2,4-triazoline)

Abstract

The solubilities and K_sp values at 25°C for the following anion salts of nitron are reported: VO₄ ⁼, Cro₄ ⁼, Cr₂O₇ ⁼,WO₄ ⁼, MoO₄ ⁼, BF₄ ^?, NO₃ ^?, NO₂ ^?, SeO₃ ⁼, S₂O₈ ⁼, SCN^?, Fe(CN)₆ ^?3, Fe(CN)₆ ^?4, Fe(CN)₅NO⁼, I^?, IO₄ ^?, CIO₃ ^?, CIO₄ ^?, BrO₃ ^?, and picrate^?. A total of 58 anions were tested.     

Growth and characterization of isotopically enriched 40Ca100MoO4 single crystals for rare event search experiments

Calcium molybdate is considered as a very promising scintillator material for experimental studies of rare processes. This paper reports on the production and characterization of a ⁴⁰Ca¹⁰⁰MoO₄ scintillator. Using the Czochralski technique, a crystal of high optical quality with total mass 0.55 kg, 42 mm diameter (minimum) and 53 mm 1ength of the cylindrical section was produced from isotopically enriched raw materials, containing 96.1% of ¹⁰⁰Mo and 99.964% of ⁴⁰Ca. To satisfy the requirement of low intrinsic radioactivity the purity of the materials was monitored at different stages of the production process and it is shown that the concentration of ²³⁸U and ²³²Th in the final crystal does not exceed 0.05 ppb. The scintillation properties of ⁴⁰Ca¹⁰⁰MoO₄ were measured over the 8 – 300 K temperature range and it is found that the light yield of the ⁴⁰Ca¹⁰⁰MoO₄ crystal is very similar to that of the CaMoO₄ reference scintillator. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Intensification of corrosion resistance of 2 K epoxy coating by encapsulation of liquid inhibitor in nanocontainer core of sodium zinc molybdate and iron oxide

A unique approach for the synthesis of an iron oxide-blended sodium zinc molybdate nanocontainer using an ultrasound-assisted method and its application for 2?K epoxy polyamide nanocomposite coatings has been presented. Sodium zinc molybdate blended with iron oxide was used as the core of the nanocontainer and layer-by-layer assembly of oppositely charged species of polyelectrolyte and inhibitor was made over this core of nanoparticles. The release of imidazole from iron oxide-blended sodium zinc molybdate nanocontainer has been quantitatively evaluated in water at different pH. It has been observed that imidazole plays a major role in the release profile of polyelectrolyte-modified nanocontainer and deciding the corrosion inhibition characteristics. Addition of 4 wt% nanocontainer in coatings results in shifting of corrosion potential (E_corr) value towards positive direction. The maximum concentration of imidazole released at the end of 1?h was found to be 0.545?mg?L^?1/g of nanocontainer at pH of 10. The results of corrosion rate analysis, Tafel plots and electrochemical impedance spectroscopy studies of an iron oxide-blended sodium zinc molybdate nanocontainer-based coatings indicated better inhibition performance compared with neat coating.     

Revised phase diagram of Li2MoO4-ZnMoO4 system, crystal structure and crystal growth of lithium zinc molybdate

Orthorhombic lithium zinc molybdate was first chosen and explored as a candidate for double beta decay experiments with ¹⁰⁰Mo. The phase equilibria in the system Li₂MoO₄-ZnMoO₄ were reinvestigated, the intermediate compound Li₂Zn₂(MoO₄)₃ of the α-Cu₃Fe₄(VO₄)₆ (lyonsite) type was found to be nonstoichiometric: Li_2−2xZn_2+x(MoO₄)₃ (0≤x≤0.28) at 600 °C. The eutectic point corresponds to 650 °C and 23 mol% ZnMoO₄, the peritectic point is at 885 °C and 67 mol% ZnMoO₄. Single crystals of the compound were prepared by spontaneous crystallization from the melts and fluxes. In the structures of four Li_2−2xZn_2+x(MoO₄)₃ crystals (x=0; 0.03; 0.21; 0.23), the cationic sites in the face-shared octahedral columns were found to be partially filled and responsible for the compound nonstoichiometry. It was first showed that with increasing the x value and the number of vacancies in M3 site, the average M3-O distance grows and the lithium content in this site decreases almost linearly. Using the low-thermal-gradient Czochralski technique, optically homogeneous large crystals of lithium zinc molybdate were grown and their optical, luminescent and scintillating properties were explored.     

Subsolidus area of the AlVO4−Al2(MoO4)3 system

The behaviour of Al₂(MoO₄)₃ towards AIVO₄ in the subsolidus area, over the whole component concentration range, has been studied using the DTA and XRD methods. The experimental results have been presented in the form of a phase diagram. It has been found that components of the system of interest do not remain in equilibrium, and AlVO₄?Al₂(MoO₄)₃ system is not a real two-component system, even in the subsolidus area.     

Preparation of iron molybdate catalysts for methanol to formaldehyde oxidation based on ammonium molybdoferrate(II) precursor

It was demonstrated that iron molybdate catalysts for methanol oxidation can be prepared using Fe(II) as a precursor instead of Fe(III). This would allow for reduction of acidity of preparation solutions as well as elimination of Fe(III) oxide impurities which are detrimental for the process selectivity. The system containing Fe(II) and Mo(VI) species in aqueous solution was investigated using UV–Vis spectroscopy. It was demonstrated that three types of chemical reactions occur in the Fe(II)–Mo(VI) system: (i) formation of complexes between Fe(II) and molybdate(VI) ions, (ii) inner sphere oxidation of coordinated Fe(II) by Mo(VI) and (iii) decomposition of the Fe–Mo complexes to form scarcely soluble Fe(III) molybdate, Mo(VI) hydrous trioxide and molybdenum blue. Solid molybdoferrate(II) prepared by interaction of Fe(II) and Mo(VI) in solution was characterized by EDXA, TGA, DTA and XRD and a scheme of its thermal evolution proposed. The iron molybdate catalyst prepared from Fe(II) precursor was tested in methanol-to-formaldehyde oxidation in a continuous flow fixed-bed reactor to show similar activity and selectivity to the conventional catalyst prepared with the use of Fe(III).