Search results for "RAV"
showing 10 items of 5866 documents
Sample preparation methods for the determination of pesticides in foods using CE-UV/MS.
2010
Much progress has been made in pesticide analysis over the past decade, during this time hyphenated techniques involving highly efficient separation with sensitive detection have become the techniques of choice. Among these, methods based on separation with mass spectrometric detection have resulted in greater likelihood of identification and are acknowledged to be extremely useful and authoritative methods for the determination of pesticide residues but the inherent advantages of the use of CE as a separation technique are well-known and can be summarized as high separation efficiency, low analysis time, high resolution power, and low consumption of samples and reagents. Although UV is the…
Spectrophotometric Determination of Hydralazine with 2-Hydroxy-1-naphthaldehyde in Pharmaceuticals
1991
Abstract A new extraction-spectrophotometric method for the determination of hydralazine, based on its reaction with 2-hydroxy-1-naphthaldehyde at 25 °C, is described. The calibration curve was linear between 0.4 and 6 mg/mL of hydralazine. The molar absorbtivity of the product at 408 nm is 40 900 L · mol − 1 · cm − 1 . The method described was applied to the analysis of hydralazine in pharmaceutical preparations containing reserpine, hydrochlorothiazide, bendrofluorthiazine, propranolol, and other substances. The agreement with the U.S.P. XXI method was satisfactory for tablets and injections, but not for pellets.
Evaluation of molecular mass and tacticity of polyvinyl alcohol by non-equilibrium capillary electrophoresis of equilibrium mixtures of a polymer and…
2011
Non-equilibrium capillary electrophoresis of equilibrium mixtures (NECEEM) has been used to characterize polyvinyl alcohol (PVA). Commercial PVA samples with different molecular masses, from M(w)=15 up to 205 kDa, were used. According to the (13)C NMR spectra, the samples also differed in tacticity (stereoregularity). Mixtures of PVA and the anionic azo-dye Congo Red (CR) were injected in the presence of a borate buffer. The electropherograms gave a band and a peak due to the residual PVA-CR complex and the excess dye, respectively, plus a superimposed exponential decay due to the partial dissociation of the complex during migration. The stoichiometry of the PVA-CR complex, q=[monomer]/[dye…
Flow injection-spectrophotometric determination of metoclopramide hydrochloride.
1997
Abstract The determination of metoclopramide hydrochloride is spectrophotometrically determined by the Bratton-Marshall method in a flow injection assembly. The required nitrite is prepared on-line in the flow assembly by reducing a nitrate solution with the aid of a copperised cadmium solid-phase reactor. The calibration graph is linear over the range 0.5–85 mg l−1, with a relative standard deviation (RSD) of 0.89%, and sample throughput of 51 samples h−1. The method is easy and simple, and it is applied to determination of metoclopramide in some pharmaceutical formulations. The method eliminates the need for frequent preparation of unstable nitrite solutions.
Comparative Study on the Determination of Cephalexin in its Dosage Forms by Spectrophotometry and HPLC with UV-vis Detection
1997
This paper discusses the spectrophotometric determination of cephalexin as the intact cephalexin or as its acid-induced degradation product. Cephalexin can be determined in the range 1 × 10−5−18 × 10−5M with relative standard deviations of 5-1%. The limits of quantitation and detection were 10−5 and 0.3 × 10−5M, respectively. These procedures were compared with reversed-phase HPLC determination. No interference was observed in the presence of common pharmaceutical adjuvants. The H-point standard additions method was applied in order to correct for the possible presence of the cephalexin precursor, 7-aminocephalosporanic acid; this improves the selectivity of the UV-vis spectrophotometric me…
Rapid and simultaneous high-performance liquid chromatography assay of polyamines and monoacetylpolyamines in biological specimens
2000
A rapid, resolutive and reproducible reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for polyamines and acetylpolyamines by adopting pre-column derivatization with benzoyl chloride. In a single run lasting less than 15 min ten polyamines were separated as well as traces of benzoic acid, methylbenzoate and benzoic anhydride. These contaminants, produced during the derivatization reaction, were almost all eliminated by washing steps envisaged in the same procedure. This simple and sensitive method can be applied to routine determination of polyamines in biological samples. A fine application of this procedure to the determination of endogenous content of p…
A new selective fluorogenic probe for trivalent cations.
2012
[EN] A new selective chromo-fluorogenic probe for Fe 3+, Cr 3+ and Al 3+ is reported. Detection limits are in the ¿M range and the fluorogenic sensing ability could be observed by the naked eye when illuminated with UV-light. No response is observed with divalent cations. © 2012 The Royal Society of Chemistry.
Covalent DNA adducts formed by benzo[c]chrysene in mouse epidermis and by benzo[c]chrysene fjord-region diol epoxides reacted with DNA and polynucleo…
1997
The metabolic activation in mouse skin of benzo[c]chrysene (B[c]C), a weakly carcinogenic polycyclic aromatic hydrocarbon (PAH) present in coal tar and crude oil, was investigated. Male Parkes mice were treated topically with 0.5 mumol of B[c]C, and DNA was isolated from the treated areas of skin at various times after treatment and analyzed by 32P-postlabeling. Seven adduct spots were detected, at a maximum level of 0.89 fmol of adducts/microgram of DNA. Four B[c]C-DNA adducts persisted in skin for at least 3 weeks. Treatment of mice with 0.5 mumol of the optically pure putative proximate carcinogens (+)- and (-)-trans-benzo[c]chrysene-9,10-dihydrodiols [(+)- and (-)-B[c]C-diols] led to th…
The crevice of the picture: Behind-the-scenes look at the early cinematographic representations of the ainu people (1897-1918)
2014
El presente trabajo plantea un recorrido histórico por la representación del pueblo ainu en el cine de los orígenes. Hemos dividido el corpus en tres bloques: primero, la presencia ainu entre las primeras actualités de los Lumière rodadas en Japón. Segundo, en las actualités de la compañía Pathé y la referencia a un documental perdido de Torii Rūyzō. Tercero, en los travelogues realizados en Japón por los exploradores en los años 10 Frederick Starr y Benjamin Brodsky. Al comparar el análisis cinematográfico con la realidad social del pueblo ainu se pone de relieve cómo los documentales trataron de proyectar una etnicidad correspondiente a un tiempo anterior al momento en que fueron filmados…
Spectroscopic study of the interaction of Ni(II)-5-triethyl ammonium methyl salicylidene ortho-phenylendiiminate with native DNA.
2009
The interaction of native calf thymus DNA with the cationic Ni(II) complex of 5-triethyl ammonium methyl salicylidene ortho-phenylendiimine (NiL(2+)), in 1mM Tris-HCl aqueous solutions at neutral pH, has been monitored as a function of the metal complex-DNA molar ratio by UV absorption spectrophotometry, circular dichroism (CD) and fluorescence spectroscopy. The dramatic modification of the DNA CD spectrum, the appearance of a broad induced CD band in the range 350-400nm, the strong increase of the DNA melting temperature (T(m)) and the fluorescence quenching of ethidium bromide-DNA solutions, in the presence of increasing amounts of the NiL(2+) metal complex, support the existence of a tig…