Search results for "Spectrophotometry"
showing 10 items of 644 documents
Reversible Colorimetric Probes for Mercury Sensing
2005
The selectivity and sensitivity of two colorimetric sensors based on the ruthenium complexes N719 [bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) bis(tetrabutylammonium) bis(thiocyanate)] and N749 [(2,2':6',2' '-terpyridine-4,4',4' '-tricarboxylate)ruthenium(II) tris(tetrabutylammonium) tris(isothiocyanate)] are described. It was found that mercury ions coordinate reversibly to the sulfur atom of the dyes' NCS groups. This interaction induces a color change in the dyes at submicromolar concentrations of mercury. Furthermore, the color change of these dyes is selective for mercury(II) when compared with other ions such as lead(II), cadmium(II), zinc(II), or iron(II). The detection limit…
Isomerization and increase in the antioxidant properties of lycopene from Momordica cochinchinensis (gac) by moderate heat treatment with UV-Vis spec…
2014
International audience; Momordica cochinchinensis (gac) is a plant rich in lycopene. This pigment tends to solubilize in oil and get damaged during extraction. The impact of heating on cis-isomerization of oil-free lycopene in hexane was studied at 50 and 80°C during 240min with UV-Vis spectrometry, DAD-HPLC and TEAC test. The initial all-trans-form isomerized to the 13-cis isomer more rapidly at 80°C. After this treatment, 16% of the lycopene compounds were in the 9-cis-form. This isomer triggered an increase in the antioxidant properties which was detectable from concentrations above 9% and resulted in a change from 2.4 to 3.7μmol Trolox equivalent. It is thus possible to increase the bio…
Interpretation and Chemometric Evaluation of the Bilirubin Interference in the Kinetic Spectrophotometry Determination of Creatinine in Serum by Use …
1992
Abstract SUMMARY In an alkaline picrate medium we demonstrated the occurrence of isosbestic points over the range 520–550 nm, the position depending on the bilirubin content and less on the albumin content. Bilirubin does not markedly modify the ratt constant of the reaction between creatinine and picrate, however, it does modify the intercept of the Ln ΔA vs t, plots. The absolute value of Ln ΔA varies with the concentration, though not with time, which indicates that bilirubin acts by consuming part of the initially present creatinine irrespective of its owr concentration at the wavelengths typically used in the creatinine determination. The Ln ΔA values at the isosbestic points coincide …
Subcellular duplex DNA and G‐quadruplex interaction profiling of a hexagonal PtII metallacycle
2019
[Abstract] Metal‐driven self‐assembly afforded a multitude of fascinating supramolecular coordination complexes (SCCs) with applications as catalysts, host–guest, and stimuli‐responsive systems. However, the interest in the biological applications of SCCs is only starting to emerge and thorough characterization of their behavior in biological milieus is still lacking. Herein, we report on the synthesis and detailed in‐cell tracking of a Pt2L2 metallacycle. We show that our hexagonal supramolecule accumulates in cancer cell nuclei, exerting a distinctive blue fluorescence staining of chromatin resistant to UV photobleaching selectively in nucleolar G4‐rich regions. SCC co‐localizes with epit…
New acetophenone glucosides isolated from extracts of Helichrysum italicum with antiinflammatory activity.
2001
Three new acetophenone glucosides (4-6), three known aglycons (1-3), and a benzo-gamma-pyrone glucoside (7) were isolated from the CH(2)Cl(2), EtOAc, and BuOH extracts from the aerial parts of Helichrysum italicum. All the compounds tested showed antiinflammatory activity in a 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced mouse ear edema test, and the ID(50) value of compound 2, the most active compound, was determined.
Comparison between sodium dodecylsulphate and cetyltrimethylammonium bromide as mobile phases in the micellar liquid chromatography determination of …
2004
The retention behaviour of non-steroidal anti-inflammatory drugs (NSAIDs) using micellar mobile phases of sodium dodecylsulphate (SDS) is studied and compared with that observed with micellar mobile phases of cetyltrimethylammonium bromide (CTAB). A liquid chromatographic procedure for the determination of acemetacin, diclofenac, indomethacin, ketoprofen, naproxen and tolmetin in pharmaceutical preparations is described. The proposed system uses a Kromasil C18 analytical column and a solution of 0.15 M SDS at pH 3 with 10% 1-propanol as mobile phase. Under these conditions, the studied NSAIDs elute between 6 and 10 min at a 1 mL min(-1) flow rate. Limits of detection (LOD) are lower than 0.…
Lanthanide complexation with CMPO and CMPO-calix[4]arenes in solution: spectrophotometric and electrospray mass spectrometric approaches.
2007
The binding of lanthanide(III) cations with organophosphorous ligands like CMPO and related calix[4]arene-based derivatives have been investigated using two experimental methods. The stability constants of the lanthanum, europium and ytterbium complexes were first determined in methanol by UV absorption spectrophotometry in the presence of nitrate or chloride anions. The results showed that the stoichiometry and the stability of the complexes formed depend on the position of the CMPO moieties either on the wide or the narrow rim of the calixarene scaffold, the nature of the medium, the conformational mobility of the ligands. Complexation of lanthanum was also followed by ESI-mass spectromet…
The influence of storage method on the transparency of pig crystalline lens
2019
Este artículo se ha publicado de forma definitiva en: http://www.scielo.br/pdf/abo/v82n1/0004-2749-abo-82-01-0056.pdf Purpose: The porcine eye is frequently used as a research model. This paper analyzes the effect of different storage methods on the transparency of pig crystalline lens. Methods: A spectral transmission curve (from 220 to 780 nm) for the crystalline lens was determined experimentally after storage in different conditions: saline solution, formalin, castor oil, and freezing at -80°C. The total transmission in the visible spectrum, which was used as an index of transparency, was calculated from these curves. For comparative purposes, fresh lenses were evaluated and used as con…
Determination of scattering in intraocular lenses by spectrophotometric measurements.
2014
This study presents a method for measuring scattering in explanted intraocular lenses (IOLs). Currently, determining scattering in IOLs is usually performed by Scheimpflug cameras and the results are expressed in the units used by this apparatus. The method we propose uses a spectrophotometer and this makes it possible to measure the total transmission of the IOL by using an integrating sphere; the direct transmission is determined by the double-beam mode. The difference between these two transmissions gives a value of the scattering in percentage values of light lost. In addition, by obtaining the spectral transmission curve, information about the most scattered wavelengths is also obtaine…
Clinical efficacy of a bleaching enzyme-based toothpaste. A double-blind controlled clinical trial.
2015
Abstract Objectives To assess the efficacy of a bleaching enzyme-based toothpaste. Material and methods A randomized clinical trial was carried out, comprising 48 participants with teeth exhibiting color A3 or higher according to the Vita Classical guide. One-half of the sample received the bleaching enzyme-based toothpaste (White Kin ® ), while the other received placebo toothpaste. Both products were supplied in identical containers and had the same composition except for the active components. The teeth color was measured with a spectrophotometer. The patients were instructed to brush their teeth three times a day during 3 min with the assigned product, during 12 weeks. The color measure…