Spectrophotometric determination of quercetin with VO2+

Summary The coloured complex formed on reaction of quercetin (3,3, 4, 5,7-pentahydroxyflavone) with vanadyl sulphate is used as the basis for a sensitive and reproducible spectrophotometric method for estimation of quercetin. The 11 complex exhibits maximum absorption at 425 nm in aqueous ethanol (80% v/v) adjusted to pH 3.3. Beer's law is followed over the quercetin concentration range of 0.3–20 g/ml. The molar absorptivity is 1.4×10⁴ l·mole^–1·cm^–1. This method can be used for the determination of quercetin isolated from biological sources. In the metal complex, the 4-carbonyl and 3-hydroxy groups of the quercetin are involved.

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Zusammenfassung Der bei der Umsetzung von Quercetin (3,3, 4, 5,7-Pentahydroxyflavon) mit Vanadylsulfat entstehende gefärbte Komplex wurde als Grundlage für eine empfindliche und reproduzierbare spektrophotometrische Bestimmung von Quercetin verwendet. Die maximale Absorption dieses 11-Komplexes beträgt in wäßrigem Äthanol (80% v/v) bei pH 3,3 und 425 nm. Bei Quercetin-Konzentrationen zwischen 0,3 und 20 g/ml gilt das Beersche Gesetz. Der molare Extinktionskoeffizient beträgt 1,4·10⁴ l· mol^–1·cm^–1. Das Verfahren kann zur Quercetinbestimmung nach Isolierung aus biologischem Material verwendet werden. An der Komplexbildung ist die 4-Carbonyl- und die 3-Hydroxygruppe des Quercetins beteiligt.

     

Strong blue emission from Pr3+ ions through energy transfer process from Nd3+ to Pr3+ via Yb3+ in tellurite glass

Energy transfer excited upconversion emission in Nd3+/Pr3+-codped tellurite glass have been studied on pumping with 800 nm wavelength. The upconversion emission bands from Pr3+ ion are observed at the 488, 524, 546, 612, 647, 672, 708 and 723 nm due to the (3P0 + 3P1)-->3H4, 3P1-->3H5, 3P0-->3H5, 3P0-->3H6, 3P0-->3F2, 3P1-->3F3, 3P0-->3F3 and 3P0-->3F4 transitions, respectively. The addition of ytterbium ions (Yb3+) on the upconversion emission intensity is also studied and result shows an eight times enhancement in the upconversion intensity at 488 nm from Pr3+ ions. The pump power and concentration dependence studies are also made. It is found that Yb3+ ions transfer its excitation energy to Nd3+ from which it goes to Pr3+. No direct transfer to Pr3+ is seen. This is verified by codoping Nd3+ and Pr3+ into the host.     

Diquark stars with extended scalar diquarks and their stability

Within the framework of an effective -theory, an attempt is made to study diquark stars and their stability with extended scalar diquarks (ESD). In this context, an equation of state (EOS) for the ESD gas is obtained. We find the EOS for the ESD gas to be stiffer than that for a point-like diquark and/or quark gas. This EOS is then used to investigate various properties of the diquark stars. In particular, the mass and radius of the maximum mass star with ESD matter turn out to be larger than those obtained with point-like diquark and/or quark matter. However, they are in conformity with the predictions available for soliton and boson stars. The stability of ESD stars against radial oscillations is also investigated. Received: 18 May 1999 / Revised version: 19 November 1999 / Published online: 14 April 2000     

Reaction of polyperoxides with triphenylphosphine

The triphenylphosphine deoxygenation of the polyperoxides, poly(styrene peroxide), poly(methyl methacrylate peroxide), and poly(α-methylstyrene peroxide) proceed via the phosphorane intermediates, which in the presence of moisture hydrolyze to give the respective diols. At higher temperatures and under dry conditions the phosphorane decomposes into epoxide and triphenylphosphine oxide. The reaction has been studied by ¹H-, ¹³C-, and ³¹P-NMR spectroscopy. The results obtained are consistent with a concerted insertion of the biphile, triphenylphosphine, into the peroxy bond and this reaction pathway seems to be new as far as the chemistry of polyperoxides is concerned. Though the aim of this investigation was to test the selective deoxygenation of polyperoxide by triphenylphosphine as a method of preparing polyethers, it turned out to be a fruitful method of synthesis of stereospecific diols. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1167–1172, 1997     

Rapid quantification of cyanamide by ultra-high-pressure liquid chromatography in fertilizer,soil or plant samples

A rapid and simple method for determination of cyanamide in fertilizer, soil and plants has been developed. In this method, cyanamide is extracted with 2% acetic acid and the extract separated by centrifugation. It is then purified by passing through a membrane filter. The extract was derivatized with 6-aminoquinolyl-N-hydroxysuccinimidyl-carbamate and the derivatized compound separated by ultra-high-pressure liquid chromatography. It is then detected with a UV detector at 260 nm by the same method as is used for amino acid analysis. The proposed method is fast, simple and cheap and also has good selectivity and sensitivity for the determination of cyanamide in a wide range of biotic and abiotic materials.     

Room-temperature ferromagnetism in Sn1−xMnxO2 nanocrystalline thin films prepared by ultrasonic spray pyrolysis

Sn_1−xMn_xO₂ (x=0.01-0.05) thin films were synthesized on quartz substrate using an inexpensive ultrasonic spray pyrolysis technique. The influence of doping concentration and substrate temperature on structural and magnetic properties of Sn_1−xMn_xO₂ thin films was systematically investigated. X-ray diffraction (XRD) studies of these films reflect that the Mn³⁺ ions have substituted Sn⁴⁺ ions without changing the tetragonal rutile structure of pure SnO₂. A linear increase in c-axis lattice constant has been observed with corresponding increase in Mn concentration. No impurity phase was detected in XRD patterns even after doping 5 at% of Mn. A systematic change in magnetic behavior from ferromagnetic to paramagnetic was observed with increase in substrate temperature from 500 to 700 °C for Sn_1−xMn_xO₂ (x=0.01) films. Magnetic studies reveal room-temperature ferromagnetism (RTFM) with 3.61×10⁻⁴ emu saturation magnetization and 92 Oe coercivity in case of Sn_1−xMn_xO₂ (x=0.01) films deposited at 500 °C. However, paramagnetic behavior was observed for the films deposited at a higher substrate temperature of 700 °C. The presence of room-temperature ferromagnetism in these films was observed to have an intrinsic origin and could be obtained by controlling the substrate temperature and Mn doping concentration.     

Type and distribution of chemical groups from controlled photo-oxidation of gyroid nanoporous 1,2-polybutadiene

Photo-oxidation of nanoporous polymers is little studied. The high UV penetration depth and high surface concentration in these materials give unprecedented possibilities both in fundamental work on surface photochemistry and in nanotechnological applications related for example to patterned hydrophilicity or refractive index. This is a quantitative study of the photo-oxidation products of nanoporous gyroid 1,2-polybutadiene in air. Irradiation of the porous sample with UV in the wavelength range of 300-400 nm enables tuning of the hydrophilicity of the nanoporous polymer through formation of hydrophilic chemical groups, carboxyl and hydroxyls, mainly onto the large air-polymer interface. The nature and abundance of the chemical groups induced by photo-oxidation is identified by solid-state ¹³C-NMR and FTIR spectroscopy. The distribution of photo-oxidation groups, both relative to the nanometre-scale polymer-air interface, and as a function of irradiation depth in the sample, is studied by gravimetry, titrimetry, ATR-FTIR and energy dispersive X-ray spectroscopy in scanning electron microscopy.     

Stability of extended scalar diquark stars vis-à-vis soliton stars

Motivated by relatively large values of the maximum mass (M = 8.92M⊙) and radius (R = 507 km) obtained for an extended scalar diquark star within the framework of an effective φ⁴-theory (S K Karnet al [1]) some interesting observations are made with regard to the stability of stellar objects describable in general in terms of the polynomial field theories     

Octahedral titanium(IV) complexes with five novel hydroximic acid ligands: Synthesis,spectroscopic characterization,and <Emphasis Type="Italic">in vitro</Emphasis> activities on IMR-32 and CHO cell lines and ten bacterial strains

Complexes with the composition TiCl₄L₂ where L = benzohydroxamic acid, 2-hydroxybenzo-hydroxamic acid, acetohydroxamic acid, hydroxyurea, and N-hydroxy-N-phenylbenzamide have been synthesized by reaction of titanium tetrachloride with 2 equiv of the corresponding hydroxamic acids. The structure of these complexes has been studied by analytical and spectroscopic (FT-IR, UV-Vis, MS, ¹H and ¹³C NMR) techniques. The free ligands and the complexes have been tested in vitro to evaluate their activities against IMR-32 (neuroblastoma) cancer cell line, CHO p-40 (Chinese hamster ovary) normal cells, and ten pathogenic bacterial strains.