Search results for "Oct"
showing 10 items of 3052 documents
Synthesis, crystal structure and magnetic properties of the malonato-bridged bimetallic chain [Mn(II)Cu(II)(mal)2(H2O)4]·2H2O
2000
Abstract The first malonato-bridged bimetallic chain of formula [MnCu(mal)2(H2O)4]·2H2O (1) (H2mal=malonic acid) was prepared and its structure determined by X-ray diffraction methods. Each copper atom in 1 is in a square planar environment formed by four malonate-oxygens from two malonate ligands. The manganese atom is six-coordinated with four water molecules and two cis-coordinated malonate-oxygens from two malonate groups building a distorted octahedral surrounding. The malonate group acts simultaneously as bidentate and monodentate ligand towards copper and manganese atoms respectively, leading to a bimetallic chain. Two structurally different carboxylato-bridges exhibiting an anti–syn…
Preparation and structural studies on the tBu2Sn(IV) complexes with aromatic mono- and dicarboxylic acids containing hetero {N} donor atom
2004
Nine complexes of 'Bu2Sn(IV)(2+) were obtained in the solid state with ligands containing -COOH group(s) and aromatic (N) donor atom. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. It was found that in most cases the -COO- groups are co-ordinated in monodentate manner. Nevertheless, in some of our complexes, the -COO- group forms bridges between two central {Sn} atoms resulting in the formation of an oligomeric structure, a motif that is characteristic only to the nicotinate compound. These pieces of information and the rationalisation of the experimental Sn-119 Mossbauer nuclear quadrupole splittings, Delta, - according to the point charge model forma…
Agencias de calificación, mercados financieros y modelos de responsabilidad
2014
Tesis doctoral inédita cotutelada por la Universitá degli Studio di Palermo, Facoltá di Giurisprudenzia, Scuola Dottorale Internazionale "Tullio Ascarelli" Diritto - Economia - Storia y la Universidad Autónoma de Madrid, Facultad de Derecho, Departamento de Derecho Privado, Social y Económico. Fecha de lectura: 17 de marzo 2014
Flow injection-chemiluminescence determination of octyl dimethyl PABA in sunscreen formulations
2002
Abstract A sensitive flow injection (FI) procedure was developed for the determination of the UV-filter octyl dimethyl PABA in sunscreen formulations based on its chemiluminescence (CL) induced by potassium permanganate in sulfuric acid. Both second-order and log–log calibration graphs can be used to perform the analysis. Ninety injections per hour can be carried out, which means a sample throughput of 18 h −1 if five injections per solution are performed. The limit of detection (3 σ ) was 25 ng ml −1 . The interference effects of the excipient and other UV filters are studied. Sunscreen formulations containing octyl dimethyl PABA were analysed by both the proposed FI-CL method and a liquid…
Determination of synthetic antioxidants in dairy products and dietetic supplements by micellar liquid chromatography with direct sample injection
2000
A simple and rapid HPLC method for the determination of synthetic antioxidants (propyl gallate, tert-butylhydroquinone, 2,4,5-trihydroxybutyrophenone, nordihydroguaiaretic acid, octyl gallate, 3-tert-butyl-4-hydroxyanisole and dodecyl gallate) in powdered and liquid milk, cream of milk and dietetic supplements is described. The samples are diluted or solved in a micellar solution, filtered and directly injected. The retention behavior of the antioxidants on a C18 column, with micellar mobile phases containing SDS (0.05–0.15 M), n-propanol (1–9%, v/v) and 10 mM phosphate at pH 3, has been studied by using mathematical models. Retention is predicted with errors below 3%. To optimize the mobil…
Direct injection of edible oils as microemulsions in a micellar mobile phase applied to the liquid chromatographic determination of synthetic antioxi…
1999
Abstract A simple and quick procedure for analysis of hydrophobic samples by direct injection in a liquid chromatograph, without previous extraction, has been developed. The sample is solved in a water/sodium dodecyl sulphate/n-pentanol microemulsion without destroying the microemulsion structure, and injected. A micellar mobile phase containing 0.1 M SDS, 2.5% n-propanol and 10 mM phosphate of pH 3 is used. The procedure is applied to the determination of synthetic antioxidants (propyl gallate, tert-butylhydroquinone, 2,4,5-trihydroxybutyrophenone, nordihydroguaiaretic acid, octyl gallate, 3-tert-butyl-4-hydroxyanisole and dodecyl gallate) in sunflower, corn and olive oils. Linear calibrat…
Determination of UV-filters in sunscreens by HPLC.
2001
Simultaneous determination of six internationally authorised organic UV-filters in sunscreen formulations was performed by HPLC with UV spectrophotometric detection. The filters determined were: sulisobenzone, oxybenzone, octyl dimethyl PABA, octyl methoxycinnamate, octyl salicylate and homosalate. A C18 stationary phase and a mobile phase of ethanol water acetic acid (70 : 29.5 : 0.5) were used with a flow rate of 0.5 mL/min. UV measurements were carried out at 313 nm. The time required for the analysis was 25 min and the limits of detection were between 0.2 and 2 mg/L, except for sulisobenzone, which gave a limit of detection of 20 mg/L. The procedure proposed provides an accurate, fast a…
Determination of the UV filters worldwide authorised in sunscreens by high-performance liquid chromatography
2001
Simultaneous determination of organic UV filters worldwide authorised in sunscreen formulations was performed by HPLC with UV spectrophotometric detection. The filters determined were: benzophenone-4, benzophenone-3, butyl methoxydibenzoylmethane, octyl dimethyl PABA, octyl methoxycinnamate, homosalate and octyl salicylate. A C18 stationary phase and an isocratic mobile phase of ethanol-water-acetic acid (70:29.5:0.5) containing 65.4 mM of hydroxypropyl-beta-cyclodextrin, were used with a flow-rate of 0.6 ml/min. UV measurements were carried out at 313 nm. The time required for the analysis was 20 min and the limits of detection were between 1.5 and 2.3 mg/l. The procedure proposed provides…