Selective extraction and separation of iron(III) with 4-methylpentan-2-ol

4-methylpentan-2-ol is used for quantitative extraction of iron(III) from 5.5-6M hydrochloric acid. The iron(III) is then stripped with water and determined titrimetrically. Te(IV), Se(IV), ascorbate, fluoride and thiocyanate interfere must be absent. Mo(VI), W(VI) and Au(III) are co-extracted but do not interfere in the determination.     

Impurity analysis of gentamicin bulk samples by improved liquid chromatography-ion trap mass spectrometry

Several gentamicin bulk samples from different origins were investigated using an LC/MS method.LC equipped with ion trap MS with positive ionization was performed on a Capcell Pak C18(AQ) column with the mobile phase containing 50 mM trifluoroacetic(TFA) and methanol.Impurities present in batches of gentamicin bulk samples were elucidated and compared according to their fragmentation behavior.In total seventeen impurities present in samples,five impurities were not elucidated and two compounds were identifi...     

Thermal Studies of Metal-quinone Complexes Role of Aqua Coligations with Copper(II) in Coordination of 2-hydroxy-1,4-naphthoquinone

Copper(II) complexes of lawsone (2-hydroxy-1,4-naphthaquinone, Lw) with variety of aqua ligation viz. Cu-1, [Cu(Lw)₂(H₂O)]₂; Cu-2, [Cu(Lw)₂(H₂O)₂] and Cu-3, [Cu(Lw)₂(H₂O)₂]₂ have been synthesized. The role of water as counter ligand on coordination propensity of redox active lawsone in naphthoquinone/naphthosemiquinone (NQ/NSQ) forms is quantified by studies of pyrolytic reactions, using non-isothermal TG and DTA techniques, coupled with IR studies. Mixed (NQ) (NSQ) ligation in Cu-1 and Cu-3 required energy of activation, E_a ∼67 kJ mol⁻¹ of (NQ) and ∼41 kJ mol⁻¹ of (NSQ). Comparable energies of aqua ligand (∼43 kJ mol⁻¹) with NSQ ligand in Cu-1 and Cu-3, dictate charge distributions in lawsone coordinations. A large difference between E_a of aqua and p-NQ ligand indicates coordination of lawsone in its fully oxidised quinone form in Cu-2. From thermoanalytical studies schematic oxidative decomposition mechanisms are proposed for Cu-1 and Cu-3. From pyrolytic reactions enthalpies are estimated by DTA technique. This revised version was published online in August 2006 with corrections to the Cover Date.     

Development and validation of a liquid chromatographic method for monitoring of process-related synthetic organic impurities of profenofos in technical products

A simple and rapid reversed-phase high-performance liquid chromatographic method for the monitoring of process-related synthetic organic impurities of profenofos (PFS) is developed. Impurities are separated and determined on a reversed-phase Hypersil C(18) column using gradient elution of 50 mM ammonium formate buffer-acetonitrile as a mobile phase and detection at 230 nm at ambient temperature. The method is validated with respect to accuracy, precision, linearity, and limits of detection and quantitation. The method is found to be suitable not only for monitoring the reactions involved in the process development of PFS, but also quality assurance, as it can detect impurities at the level of 1.5 x 10(-8) g.     

Dark Energy： Relating the Evolutions of the Universe from the Past to the Future

Using the evolution history of the universe, one can make constraint on the parameter space of dynamic dark energy models. We discuss two different parameterized dark energy models. Our results further restrict the combined constraints obtained from supernova and the first-year Wilkinson-microwave-anisotropy-probe observations. From the allowed parameter space, it is found that our universe will experience an eternal acceleration. We also estimate the bound on the physically relevant regions both in the re-inflationary and inflationary phases.