Development of a method for the determination of danofloxacin in plasma by HPLC with fluorescence detection

A simple and sensitive HPLC method has been developed for the determination of danofloxacin (DAN) in plasma. Sample preparations were carried out by adding phosphate buffer (pH 7.4, 0.1 M), followed by extraction with trichloromethane. DAN and the internal standard, sarafloxacin (SAR), were separated on a reversed-phase column, and eluted with aqueous solution-acetonitrile (80:20 v/v). The fluorescence of the column effluent was monitored at lambda(ex) = 338 and lambda(em) = 425 nm. The retention times were 2.80 and 4. 40 min for DAN and SAR, respectively. The method was shown to be linear from 1 to 1500 ng/mL (r(2) = 0.999). The detection and quantitation limit were 1 and 5 ng/mL, respectively. Mean recovery was determined as 80% by the analysis of plasma standards containing 150, 750 and 1500 ng/mL. Inter- and intra-assay precisions were 4.0% and 2.4%, respectively.     

Determination of atomic parameters from powder diffraction intensity ratios

The basis for a systematic use of intensity ratios is given in order to determine positional and occupational parameters. Given a series of N powder diffraction intensities, the matrix of intensity ratios is defined. Expressing them as vectors, it is shown that they form a subset of $\text{1}\text{2}\text{(N}{}^2\text{? N)}$ elements in a vectorial space with dimension N ? 1. Since any intensity ratio may be obtained from the product or division of other ratios, their vectorial representation is used to define a criterion for independence for a set of ratios, transforming the product in a sum of the corresponding vectors. Any set of N ? 1 independent ratios may be used in the determination of atomic parameters. In order to find the most suitable set, it is proposed to assign an index to each intensity ratio, which depends upon the difference between observed and calculated values and their derivatives with respect to the parameters to be determined. Then, an independent set of intensity ratios is chosen among those with higher indices, for each point of a convenient grid in the space of the parameters, finding the best set at each point. Finally, the best absolute set is defined as that with the minimum value of an agreement indicator between observed and calculated values. An illustrative example of the procedure indicated above is shown, and the results are compared with those obtained by other powder integrated intensity methods. In this work, comparison with the Rietveld profile refinement method is not considered.     

Crystal and molecular structure of a 1:1 complex of potassium perchlorotriphenylmethide and 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane)

(C₆Cl₅)₃ C^– K⁺, C₁₂H₂₄O₆ is monoclinic, space groupP2₁ withZ=2,a=10.491(2),b=18.016(7),c=11.670(6) , =103.11(3)°,V=2148(1) ³, finalR=0.039 for 2339 observed reflections at room temperature. The overall shape of the perchlorotriphenyl free radical is given by the angles between the mean planes of each ring (around 70°). The K⁺ ion lies at the centre of the 18-membered macrocyclic ring. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. 82012 (19 pages).     

Systematic synthesis and characterization of the derivative complexes of the tetrafluoroaminechromate(III) Anions. — crystal structure of the (en-H2)[CrF4(en)]Cl

Summary The new complexes (aa-H₂)[CrF_4(aa)]Cl, where aa = ethylenediamine, 1,2-diaminopropane or 1,2-diaminocyclohexane, have been systematically synthesized and characterized. The crystal structure of (en-H₂)[CrF₄(en)]Cl (en = ethylenediamine) has been resolved indicating that the four fluorine atoms are ligands and the chloride is ionic. The cation is the diprotonated ethylenediamine ligand. Synthesis of the analogous complex with 1,3-diaminopropane (tn) failed. The hydrolysis of these complexes with concentrated HBr give compounds of formula [CrF₂(H₂O)₂(aa)]Br, which upon solid phase heating yield the dehydrated [CrF₂Br(H₂O)(aa)].     

Syntheses and magneto-structural study of several polynuclear copper(II) complexes derived from 1,3-Bis(dimethylamino)-2-propanolato

The syntheses, structural characterization, and magnetic behavior of the three new polynuclear copper(II) complexes with formulas [Cu(4)(eta(2):mu-CH(3)COO)(2)(mu-OH)(2)(mu-OH(2))(mu-bdmap)(2)](ClO(4))(2).H(2)O (1), [Cu(8)(NCO)(2)(eta(1):mu-NCO)(4)(mu-OH)(2)(mu(3)-OH)(2)(mu-OH(2))(3)(mu-bdmap)(4)](ClO(4))(2)x2H(2)O (2), and [Cu(9)(eta(1):mu-NCO)(8)(mu(3)-OH)(4)(OH(2))(2)(mu-bdmap)(4)](ClO(4))(2).4H(2)O (3), in which bdmapH is 1,3-bis(dimethylamino)-2-propanol, are reported. Tetranuclear complex 1 crystallizes in the triclinic system, space group P, with unit cell parameters a = 12.160(1) A, b = 13.051(1) A, c = 13.235(1) A, alpha = 110.745(1) degrees , beta = 109.683(1) degrees , gamma = 97.014(1), and Z = 2. Octanuclear complex 2 crystallizes in the monoclinic system, space group C2/c, with unit cell parameters a = 26.609(1) A, b = 14.496(1) A, c = 16.652(1) A, beta = 97.814(1) degrees , and Z = 4, and nonanuclear complex 3 crystallizes in the monoclinic system, space group C2/c, with unit cell parameters a = 24.104(1) A, b = 13.542(1) A, c = 24.355(1) A, beta = 109.98(1) degrees , and Z = 4. The magnetic behavior of the three complexes has been checked showing strong antiferromagnetic coupling in all the cases.     

Synthesis,resolution, and reactivity of benzylmesitylphenylphosphine: a new p-chiral bulky ligand

The synthesis of P,P'-dimesityl-P,P'-diphenyldiphosphine and benzylmesitylphenylphosphine is described as well as the resolution of the latter ligand by means of homochiral organometallic complexes. The absolute configuration of the phosphine is assigned by NMR spectra, using the homochiral palladacycle as a reference point. The configuration has been confirmed by single crystal X-ray diffraction. Molecular mechanics calculations were performed in [PdCl-(R)-(+)-C10H6CH(Me)NH2(PBnMesPh)], and showed that the rotation around the Pd-P bond is restricted in this complex. [Pd(eta3-2-MeC3H4)Cl(PBnMesPh)] was obtained and used as a precursor in the catalytic hydrovinylation of styrene. Benzylmesitylphenylphosphine has a strong tendency to form phosphapalladacycles by activation of one of the ortho-methyl groups. The formation of this metallacycle from cyclopalladated N-donor derivatives by a ligand-exchange reaction is also described.     

High-volume sampling of airborne polychlorobiphenyls with amberlite xad-2 resin

Polyurethane foam, polyurethane foam coated with DC-200, Florisil, and Amberlite XAD-2 resin have been evaluated in a small-scale comparative study of their ability to sample airborne polychlorobiphenyls. XAD-2 resin has an excellent collection efficiency for tetrachlorobiphenyl at 1 l min^-1 flow rates and is also suitable for high-volume air sampling. A high-volume air sampler was modified to sample both particulate and vapor-phase polychlorobiphenyls by incorporating the XAD-2 resin behind a glass fiber filter. When the sampling system was operated at a flow rate of 0.7 m³ min^-1 for 24 h, the collection efficiencies for tetrachlorobiphenyl and Aroclor 1221 were 96.5% and 83.0%, respectively.     

Free-radical polymerization of styrene in worm-like micelles

The solubilization of styrene in wormlike micelles of the cationic surfactant, cetyltrimethylammonium tosilate (CTAT), and its polymerization is examined here by UV spectroscopy, oscillatory rheometry, small angle X-ray scattering, polarizing light microscopy, and transmission electron microscopy. At low CTAT concentrations, the polymerization of styrene yields small and rigid rods in coexistence with wormlike micelles that form from the excess surfactant after the polymerization process. At high CTAT concentrations, polymeric rods (of large aspect ratio), spheroid polymer particles, and wormlike micelles coexist. The polymerization rate is second order, indicating that polymerization reactions end mainly by bimolecular termination.     

Morpholine‐2,5‐dione

In the title compound, C₄H₅NO₃, the morpholine ring adopts a boat conformation that is distorted towards twist–boat, the boat ends being the two Csp³ atoms of the ring. The mol­ecular packing is stabilized by the establishment of strong inter­molecular NH⋯OC hydrogen bonds, which give rise to centrosymmetric dimers, and a network of weak CH₂⋯OC hydrogen bonds, where each dimer inter­acts with eight neighbouring morpholine­dione rings.