Search results for "Fluorescence"
showing 10 items of 2463 documents
Photochemical derivatization and fluorimetric determination of reserpine in a flow-injection assembly
1991
Abstract The fluorimetric flow-injection determination of reserpine was achieved with the drug being derivatized on-line by photoreaction. PTFE tubing was helically coiled around a germicide lamp located between the injection valve and detector. Two analytical procedures are proposed using either dilute acetic acid or pure methanol as the carrier stream. The influence of foreign compounds was studied and the method was applied to the determination of reserpine in pharmaceutical formulations.
Stability of tocopherols in adapted milk-based infant formulas during storage
2004
Abstract An evaluation is made of the effects of added α -tocopherol ( α -T) or α -tocopherol acetate ( α -TAc) combined with iron lactate or sulfate, storage time (up to 17 months) and storage temperature (22°C and 37°C) on the α -TAc, α -T, γ -tocopherol ( γ -T) and δ -tocopherol ( δ -T) content of infant formulas. Tocopherols were measured by normal phase HPLC and fluorescence detection after direct extraction, which allows the determination of both α -TAc and α -T. The α -TAc content was not affected by temperature or storage time, although the α -, γ - and δ -T contents, which were lower at 37°C than at 22°C, were significantly affected. The type of iron salt added (lactate or sulfate)…
Determination of α-Tocopherol in Plasma by High Performance Liquid Chromatography with Fluorescence Detection and Stability of α-Tocopherol under Dif…
2011
In order to study the clinical effects of the antioxidant alpha-tocopherol (tocofersolan, CAS 30999-06-5) a simple, robust, sensitive and reliable high performance liquid chromatography (HPLC) method using fluorescence detection for the daily measurement of alpha-tocopherol concentration in plasma is described. Several methods of HPLC analysis using fluorescence techniques are published, however, investigations of the stability of alpha-tocopherol during sample preparation under different conditions are relevant in the routine measurements and have to date not been reported. Therefore a modified method, both sensitive and robust, qualified for the day-by-day measurement of alpha-tocopherol …
Estimation of the Compatibility Between Poly(Methylmethacrylate) and Poly(Styrene Co Vinyl Phenol) Blends from Dilute Solution Measurements
2006
Abstract The compatibility of poly(methyl methacrylate) (PMMA) with poly(styrene‐co‐vinyl phenol) (PS‐VPh) with two different contents of vinyl phenol, 5.8 and 7.2%, in dilute tetrahydrofuran solutions has been investigated by size exclusion chromatography and fluorescence spectroscopy at 25°C. The chromatographic technique permits the evaluation of the preferential solvation at different PMMA/PS‐VPh ratios. Changes in the fluorescence properties of PS‐VPh, caused by its association with PMMA, were used to obtain the fraction of copolymer bound to PMMA at diverse PMMA compositions. Both techniques agree quantitatively in every system, indicating that the association increases when the PMMA …
A Microplate Assay for DNA Damage Determination (Fast Micromethod)in Cell Suspensions and Solid Tissues
1999
Abstract A rapid and convenient procedure for DNA damage determination in cell suspensions and solid tissues on single microplates was developed. The procedure is based on the ability of commercially available fluorochromes to interact preferentially with dsDNA in the presence of ssDNA, RNA, and proteins at high pH (>12.0), thus allowing direct measurements of DNA denaturation without sample handling or stepwise DNA separations. The method includes a simple and rapid 40-min sample lysis in the presence of EDTA, SDS, and high urea concentration at pH 10, followed by time-dependent DNA denaturation at pH 12.4 after NaOH addition. The time course and the extent of DNA denaturation is followed …
Critical study of and improvements in chromatographic methods for the analysis of type B trichothecenes
2001
Various analytical methods used in the analysis of type B trichothecenes (deoxynivalenol, nivalenol, 3- and 15-acetyldeoxynivalenol) in cereals were compared and optimised in this work. These methods use either GC-electron-capture detection (ECD) of trimethylsilyl, trifluoroacetyl and heptafluorobutyryl derivatives or HPLC with UV or photodiode array detection of analytes. A new HPLC procedure using fluorescence detection prior derivatisation with coumarin-3-carbonyl chloride has been also tested. Five extraction solvents and two solid-phase extraction cartridges (silica, Florisil) plus a especial clean-up column (MycoSep 225) were compared in order to obtain the best recovery of the mycoto…
H-point standard additions method for resolution of overlapped chromatographic peaks with a conventional fluorescence detector. Determination of phen…
1996
The H-Point Standard Additions Method (HPSAM) is proposed in order to resolve overlapping peaks in liquid chromatography by using a conventional fluorescence detector. The method uses as analytical signals the heights or the areas obtained at two previously selected emission wavelengths, and good results are obtained for highly overlapping peaks with highly overlapping fluorescence spectra. The principal benefits of the method are the ease of finding the required wavelengths, its insensitivity to changes in the retention time of the peak from one injection to another, and the possibility of using it in highly or only partially overlapping peaks. We have applied the method to the determinati…
A rapid spectrofluorimetric method for the determination of the degree of synchronism inSaccharomyces cerevisiae
1985
A fluorescence technique that allows direct measurement of DNA and synchrony levels inSaccharomyces cerevisiae cell cultures is reported. The spectrofluorimetric estimation of DNA with 4,6-diamidino-2-phenylindole (AT-dye) does not require prior extraction, is highly stable, and requires small quantities of cells.
Quantitative Bestimmung von Gelatine in Arzneizubereitungen durch HPLC mit fluorimetrischer Detektion
1986
Gelatine ist als pharmazeutischer Hilfsstoff fur Kapseln, Gele, Globuli und Tabletten sowie als Lebensmittelzusatzstoff unverandert wichtig. Aus Proteinen hoher Molekularmasse1 bestehend, ist Gelatine spezifischen quantitativen Bestimmungen relativ schwer zuganglich2-6.
Comparison of spectrophotometric and HPLC methods for determining sialic acid in infant formulas
2011
Abstract Two methods for determining sialic acid in infant formulas – spectrophotometry and HPLC with fluorescence detection – have been optimised and validated, the first one allows to determine total sialic acid while the second allows to differentiate the two main forms of sialic acid (N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc)). A common sample preparation procedure (hydrolysis and purification) for both methods has been proposed. The linearity (from 6 to 150 μg of total sialic acid in the assay for spectrophotometry, and from 12.5 to 250 ng and 1 to 5 ng of Neu5Ac and Neu5Gc, respectively, for HPLC) is adequate. The detection and quantification limits (0.29…