Flow-injection spectrophotometric determination of dipyrone in pharmaceutical formulations using ammonium molybdate as chromogenic reagent

A simple and rapid flow-injection spectrophotometric method is reported for the determination of dipyrone in pharmaceutical formulations. The method is based on the reaction of dipyrone with ammonium molybdate in acidic medium to produce blue molybdenum, which was detected spectrophotometrically at 620 nm. The analyte was determined in a single-line flow system. The calibration curve obtained was linear in the range of 5x10(-4) to 8x10(-3) mol L-1 for dipyrone concentration and the precision ( s r =1.7%) was satisfactory. The method proved to be selective and adequately sensitive. Application of the method to the analysis of pharmaceutical samples resulted in excellent accuracy; the percent mean recoveries were in the range 95.3%-101% and relative errors less than 5.0% for five pharmaceutical formulations were found.

Flow-injection spectrophotometric determination of dipyrone in pharmaceutical formulations using ammonium molybdate as chromogenic reagent

A simple and rapid flow-injection spectrophotometric method is reported for the determination of dipyrone in pharmaceutical formulations. The method is based on the reaction of dipyrone with ammonium molybdate in acidic medium to produce blue molybdenum, which was detected spectrophotometrically at 620 nm. The analyte was determined in a single-line flow system. The calibration curve obtained was linear in the range of 5x10(-4) to 8x10(-3) mol L-1 for dipyrone concentration and the precision ( s r =1.7%) was satisfactory. The method proved to be selective and adequately sensitive. Application of the method to the analysis of pharmaceutical samples resulted in excellent accuracy; the percent mean recoveries were in the range 95.3%-101% and relative errors less than 5.0% for five pharmaceutical formulations were found.

ISOLATION AND PROPERTIES OF MOLYBDENUM SERIES OF HETEROPOLY BLUE WITH KEGGIN STRUCTURE

The present paper reports the methods for preparing and isolating 8 kinds of 1:12 molybdenum series of heteropoly blue complexes KyHzXMo12O40 . nH2O (X=Si, P, As, Ge). The products were characterized by elemental analyses, potential titration, polarograms, cyclic voltammetry, IR spectra, visible-UV spectra, X-ray powder diffraction, XPS and P-31 NMR. The single crystal structure of 4-electron molybdenum-silicon heteropoly blue was measured and the positions of reduced molybdenum atoms were determined, i.e. they were located at Mo(3), Mo(7), Mo(8) and Mo(10). The experimental results show that the heteropoly blue remains Keggin structure. ESR spectra of heteropoly blue solids were first studied, from which it was found that the delocalization extent of 2-electron heteropoly blue and 4-electron heteropoly blue is smaller than that of 1-electron heteropoly blue. The study of thermal properties shows that the thermal stability increases with the increase of the reduction extent of heteropoly blue. The study of redox properties shows that the oxidizing power order of heteropoly blue changes in different mediums, and the polarographic half-wave voltage is found to be dependent on the electronegativity of the hetero atom linearly. It is found that the phosphorus heteropoly blue and arsenic heteropoly blue show a strong anti-acid property.

THE SYNTHESIS AND CRYSTAL-STRUCTURE OF MOLYBDENUM-SILICON BLUE

The single crystal of heteropoly blue, HsSiMo12O40.12H2O, the reduced product of molybdenum-silicon heteropoly acid, was prepared by electrochemical reduction and evaporation in nitrogen atmosphere. The Crystal structure of the product was determined. The heteropoly blue H8SiMo12O40.12H2O, Crystallizes space group P1BAR a = 1.3769 (3) nm, b = 1.4346 (4) nm, c = 1.4134 (4) nm, alpha = 120.47 (2)-degrees, beta = 110.70 (2)-degrees, gamma = 66.11 (2)-degrees, Z = 2, R = 0.0608. The heteropoly blue anion was determined to have Keggin Structure and alpha-isomer and it remained the structure of the unreduced heteropoly acid anion. But the distortion of the structure and the changes of bond length and bond angle take place obviously. The four Mo5+ Positions were determined in the structure.

Morphology-controllable synthesis and characterization of single-crystal molybdenum trioxide

Molybdenum trioxide nanobelts and prism-like particles with good crystallinity and high surface areas have been prepared by a facile hydrothermal method, and the morphology could be controlled by using different inorganic salts, such as KNO3, Ca(NO3)(2), La(NO3)(3), etc. The possible growth mechanism of molybdenum trioxide prism-like particles is discussed on the basis of the presence of HI and the modification of metal cations. The as-prepared nanomaterials are characterized by means of powder X-ray diffraction (PXRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and ultraviolet and visible spectroscopy (UV-vis). TEM and HRTEM micrographs show that the molybdenum trioxide nanobelts and prism-like particles have a relatively high degree of crystallinity and uniformity. BET specific surface areas of the as-prepared molybdenum trioxide nanocrystals are 67-79 m(2)g(-1). XPS analysis indicates that the hexavalent molybdenum is predominant in the nanocrystals. UV-vis spectra reveal that the direct band gap energy of the annealed molybdenum trioxide prism-like particles shows a pronounced blue shift compared to that of bulk MoO3 powder.

A chromic molybdenum phosphate with a tunnel structure: hydrothermal synthesis and structure of (NH3CH2CH2NH3)(2) center dot (NH3CH2CH2NH2)(3)center dot[NaCr2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 6H(2)O

A chromic molybdenum phosphate, (NH3CH2CH2NH3)(2).(NH3CH2CH2NH2)(3).[NaCr2Mo12O30(PO4)(HPO4)(3)]. 6H(2)O, involving molybdenum present in V oxidation, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction and IR spectrum. Deep brown-red crystals are formed in the triclinic system, space group P (1) over bar, a = 12.067(2), b = 14.677(3), c = 21.290(2) Angstrom, alpha = 80.940(10)degrees, beta = 82.960(10)degrees, gamma = 76.61(2)degrees. The structure of the title compound may be considered to be two [Mo6O15(HPO4)(H2PO4)(3)](5-) units bonded to a chromic atom, although several P-O groups are not protonated on account of coordination with a Na+ cation. The one-dimensional tunnels were formed in the solid of the title compound. (C) 2000 Elsevier Science B.V. All rights reserved.

A manganese molybdenum phosphate with a tunnel: hydrothermal synthesis, structure and catalytic properties of (NH3CH2CH2NH3)(10-)H3O)(3)(H5O2)Na-2[MnMo12O24(OH)(6)(PO4)(4)(PO3OH)(4)]-[MnMo12O24(OH)(6)(PO4)(6)(PO3OH)(2)] center dot 9H(2)O

A manganese molybdenum phosphate, (NH3CH2CH2NH3)(10)(H3O)(3)(H5O)Na-2[MnMo12O24(OH)(6) (PO4)(4)(PO3OH)(4)][MnMo12O24 (OH)(6)(PO4)(6)(PO3OH)(2)]. 9H(2)O, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. The structure of this compound may be considered to be two [Mo6O12(OH)(3)(PO4)(2)(HPO4)(2)](7-) units bonded together by a manganese atom, although several P-O groups are not protonated on account of coordination to a Na+ cation. One-dimensional tunnels were formed in the solid. A probe reaction of the oxidation of acetaldehyde with H2O2 using this compound as catalyst was carried out in a liquid-solid system, showing that the manganese molybdenum phosphate has high catalytic activity in the reaction.

A nickel molybdenum phosphate with tunnel: Hydrothermal synthesis and structure of (NH3CH2CH2NH3)(4)center dot(NH3CH2CH2NH2)center dot Na center dot[Ni2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 6H(2)O

A nickel molybdenum phosphate, (NH3CH2CH2NH3)(4).(NH3CH2CH2NH2). Na .[Ni2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]. 6H(2)O, invoicing molybdenum present in V oxidation, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Deep brown-red crystals are formed in the triclinic system, space group P (1) over bar, a = 12,011(2), b = 14,612(3), c = 21.252(4) Angstrom, alpha = 80.54(2)degrees, beta = 83.10(2)degrees, gamma = 76.29(2)degrees, V = 3561.4(12) Angstrom(3), Z = 2, lambda(MoK alpha) = 0.71073 Angstrom (R(F) = 0.0529 for 9880 reflections), Data mere collected on a Siemens P4 diffractometer at 20 degrees C in the range of 1.75 degrees < theta < 23.02 degrees using the omega-scan technique. The structure was solved by direct methods using the program SHELXTL-93 and refined with the method of fun-matrix least-squares on F-2. The structure of the title compound may be considered to be two [Mo6O15(HPO4)(H2PO4)(3)](5-) units bonded together with a nickel atom, although several P-O groups are not protonated on account of coordination with a Na+ cation, The one-dimensional tunnels were formed in the solid of the title compound. A probe reaction of the oxidation of acetaldehyde with H2O2 using the title compound as catalyst was carried out in a liquid- solid system, showing that the title compound had high catalytic activity in the reaction, (C) 1999 Academic Press.

A ferric molybdenum phosphate with a tunnel: hydrothermal synthesis and structure of (NH3CH2CH2NH3)(2)center dot(NH3CH2CH2NH2)(3)center dot Na center dot[Fe2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 7H(2)O

A new ferric molybdenum phosphate containing a tunnel structure and crystallographically different clusters has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. A probe reaction of the oxidation of acetaldehyde with H2O2 using the tide compound as catalyst was carried out in a liquid-solid system, showing that the title compound had high catalytic activity in the reaction. (C) 1998 Elsevier Science S.A. All rights reserved.

Electrochemical preparation of microelectrodes modified with non-stoichiometric mixed-valent molybdenum oxides

A compact non-stoichiometric molybdenum (VI, V) oxide of blue film was grown on carbon fiber (CF) microelectrode surface be cycling the potential between + 0.2V and - 0.70V in a freshly prepared Na2MoO4 solution containing 5 x 10(-3) mol/L H2SO4. The quantity-of the oxide is controlled by the charge passing the electrode. The electrochemical pretreatment of CF microelectrode not only mises the deposition velocity of molybdenum oxide on CF surface, but also improves greatly the cyclic voltammetric behavior of the molybdenum oxide film prior to the electrodeposition. The cathodic processes are believed to yield the hydrogen molybdenum oxide bronzes HxMoO3(0 < x < 2), or substoichiometric lower molybdenum oxides with the formula MoO3-y(0 < y < 1). The anodic response results from the reversible oxidation of molybdenum bronze/Mo(V) centers [or perhaps Mo(IV) in more reduced coatings], to Mo(VI). Further information was gained about the chemical composition and valent state of Mo from XPS and SEM.

ELECTROCATALYTIC PROPERTIES OF MIXED-VALENCE MOLYBDENUM OXIDE THIN-FILM MODIFIED MICROELECTRODES

A compact blue conducting mixed-valence Mo (VI,V) oxide film was grown on the surface of a carbon fibre (CF) microelectrode by cycling the potential between +0.20 and similar to 0.70 V SCE in freshly prepared Na2MoO4 solution in H2SO4 (pH 2). The thicknes

ELECTROCHEMICAL PREPARATION OF MICROELECTRODES MODIFIED WITH NONSTOICHIOMETRIC MIXED-VALENT MOLYBDENUM OXIDES

A blue, conductive, compact, mixed-valent Mo(VI, V) oxide film was grown on carbon fiber (CF) microelectrode surface by cycling the potential between +0.20 and -0.70 V vs. SCE in a fresh prepared Na2MoO4 solution (pH = 2, H2SO4). The thickness of the oxid

Synthesis and characterization of solid molybdenum(VI) complexes with glycolic, mandelic and tartaric acids. Photochemistry behaviour of the glycolate molybdenum complex

The complexes (NH4)(2)[ MoO2( C2H2O3)(2)]center dot H2O, (NH4)(2)[MoO2(C8H6O3)(2)] and (NH4)(2) [MoO3(C4H4O6)]center dot H2O were prepared by reaction of MoO3 with glycolic, mandelic and tartaric acids, respectively. The complexes were characterized by elemental and thermal analysis, IR spectroscopy and X- ray diffraction. Crystals of the glycolate and tartarate complexes are orthorhombic and the mandelate complex is monoclinic. Elemental and thermal analysis data showed that the glycolate and tartarate complexes are monohydrated. Hydration water is not present in the structure of the mandelate complex. IR spectra showed COO- is involved in coordination as well as the oxygen atom of the deprotonated hydroxyl group of the alpha-carbon. The glycolate molybdenum complexes with general formula M-2[MoO2(C2H2O3)(2)]center dot nH(2)O, where M is an alkali metal and n=1 or 1/2, were also prepared and characterized. Aqueous solutions of the glycolate complex become blue and mandelate and tartarate complexes change to yellow or brown when exposed to UV- radiation.

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